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Due to the long underwater propagation delays, the underwater sink node may not receive all of the requests to send RTS and DATA frames from the various underwater sensor nodes, resulting in massive collisions. We proposed an underwater Medium Access Control (MAC) protocol that takes into account the long propagation delay to evaluate the performance of the carrier sense multiple access collision avoidance (CSMA/CA) protocol utilizing a loop-based single hope underwater sensor network. The proposed protocol is designed to restore multiple RTS control packets from n underwater sensor nodes to the underwater sink node in a single slot time. The sink node received multiple RTS frames without overlapping because the n underwater sensor nodes transmitted the RTS frames at the same time, but they were received at different times at the receiver end due to differences in propagation delays that depend on the distances between the n sensor nodes and the sink node. In this paper, by altering the number of underwater sensor nodes and the size of the contention window, the proposed MAC protocol throughput is evaluated by using the underwater propagation delay.

Due to the influence of underwater acoustic multipath channel and lack of prior information, the likelihood-based MPSK modulation identification method is facing great challenges. Therefore, we proposed an identification method combining the orthogonal matching pursuit (OMP) and expectation maximization (EM) in single input and multiple output (SIMO) underwater acoustic channel. First, the blind channel is estimated and equalized by the OMP. Then, the EM is used to compensate the recovered constellation. Finally, the likelihood-based method is applied to identify the MPSK modulation. Numerical results show the proposed method can achieve more than 95% identification rate while the SNR is higher than 7 dB.

In this modern era of Internet, E-learning is very popular among Internet users, users utilize Internet to learn from their homes with little or less effort. However the need to upgrade the suite to counter the ever increasing needs of internet was recognized and IPv6 suite was approved in 1994. IPv6 not only overcomes the issue of depletion of network addresses but also provides various other features such as automation, scalability, security, and others such as multicasting etc. Migration to IPv6 is dependent on its performance against the IPv4 implemented system. In this paper evaluation of various performance metrics of e-learning network performance on IPv4 vs IPv6 implemented system were considered. The results show the difference in the performance which must be considered when adopting the newer version and/or its implication on the end-system application. A comparison of performance of IPv6 on the Linux operating system against other popular operating system such as Windows and MacOS was noted. Overall it was shown by results that the Linux implementation of e-learning over IPv6 outperformed the other commodity operating system.

A ternary nanocomposite of Fe3O4@rGO@AgI was successfully synthesized by reflux method for photodegradation of phenol. The prepared nanocomposite was characterized for the physicochemical properties through XRD, FESEM, TEM, TGA, FTIR, and PL spectroscopy techniques. Fe3O4@rGO@AgI exhibited higher photocatalytic performance of 99% phenol degradation compared to 62, 75 and 78% using Fe3O4, Fe3O4@rGO and Fe3O4@AgI nanocomposites, respectively. The superior photocatalytic performance was mainly attributed to the rapid transportation of photogenerated electrons from GO nanosheets to AgI. The addition of H2O2 has further enhanced the phenol degradation and was the optimized loading amount of 0.4 g/350 mL achieved the highest degradation efficiency. The findings revealed that basic conditions, initial phenol concentration and catalyst amounts have significant influence on the photocatalyst performance. The 81% recyclability after five continuous cycles implied the excellent stability of the photocatalyst for practical applications.

The WSNs (Wireless Sensor Networks) lead to great opportunities to explore it scientifically. In this network different numbers of SN (Sensor Nodes) are deployed in a specific area to gather information. The UWSNs (Underwater Wireless Sensor Networks) is a highly distributed network of sensor nodes deployed underwater to gather environmental information. Hence, acquirement of real-time data at enhanced data rate and to reduce power consumption is a key concern while designing routing protocol for UWSNs. In this paper, a cooperation based solution is suggested. The solution proposed here uses the DF (Decode and Forward) strategy for relying the information from the source to the destination using a relay node. The signals coming towards the destination are weighted and combined on the basis of their SNRC (Signal to Noise Ratio Combing). The simulation results verify enhancement in different factors, required for evaluation of a UWSN. After implementation of the proposed solution the stability of the network is increased which maximize the PDR (Packet Delivery Ratio). In our proposed solution the transmission is based on channel estimation, an estimate is made for higher reliable channel, which reduces retransmission of packets. Hence, sink receive the packets with lesser delay and as a result E2E (End-to-End) delay is decreased. Data is forwarded using data forwarding by neighbor nodes. It improves average energy consumption of the system. Hence the overall performance and lifetime of a UWSN is increased.

Graphene based conducting polymer composites are emerging contenders for newer optoelectronics devices like solar cells and linear / nonlinear optical devices. Beside these advanced applications, characterization approaches to analyze their liner/nonlinear optical constants, surface chemical state and structural analysis in thin film states are much needed. Herein, we reported a facile approach for the fabrication of graphene oxide (GO) and polyaniline (PANI) nano composites (PANI/GO) thin films using spin coating. Thereafter, the liner/nonlinear optical constants including first and third order nonlinear optical susceptibility were calculated using UV–vis (UV–vis) near infra-red absorption spectroscopic technique which will be an alternative to Z-scan approach and is poorly explored till now for such composites. Moreover, the increase or decrease in elemental bonding or interactions between C C, C O, C O C, C N and percentage occurrence of C OH, O C O, –NH2, –N+H=, and –N+H2– functionalities in PANI/GO composites were concisely explored using X-ray photoelectron spectroscopy (XPS). Addition to proving the amorphous nature of PANI/GO composites in their X-ray diffraction studies, an increase in intensity of GO peak was explored due to an increase in elemental interactions among the GO and PANI. The reduction in band gap (3.27 to 2.66 eV) and diameter of Sp2 carbon (19.62 to 15.96 nm) of PANI/GO thin films was observed with an increase in the GO concentration. The first order nonlinear optical susceptibility (X (1)) is influenced by π-π* and n- π* interaction. The third order nonlinear optical susceptibility (X (3)) was found in the range of 10−10 to 10-7 esu which can be further, optimized by changing the ratio of GO and PANI.

Graphene oxide (GO) belongs to carbon family with honeycomb structure having hydroxide, carbonyl, and carboxylic moieties at its basal plane. These functionalities are decreased in reduced graphene oxide (rGO), and this boosts the intrinsic properties of GO. Herein, in this work, the effect on physical and chemical properties of GO and rGO in combination with copper-doped zinc oxide (Cu–ZnO) thin films, prepared via DC/RF sputtering, was investigated for the very first time. The deposition of Cu–ZnO over rGO (Cu–ZnO@rGO) showed remarkably superior properties and presented an extension in d-spacing without preferred plane orientation of Cu–ZnO plane, and this was found to be due to its hydrophobic nature. The decrease in band gap of composite thin films was due to the surface electric charge conducted by GO or rGO. The enhanced dielectric constant is attributed due to increase in electron–hole pairs owing to the increase in sp2 hybridization. However, sp2 network was also found to be responsible to provide the conductivity path way which increases the dielectric loss in Cu–ZnO@rGO thin films as compared to that in Cu–ZnO@GO; this might be due to aggregation of Cu–ZnO nanoparticles over the rGO films in comparison with GO as evident from the morphological analysis by AFM. The change in surface chemistry was ascribed with the ratio of COOH, C=O, C–OH and C–C bonding in the Cu–ZnO@GO and Cu–ZnO@rGO thin films as unveiled in their XPS analysis. The developed thin films exhibited enhanced antimicrobial activity against E. coli and E. faecalis which might be due to the synergistic effects of Cu–ZnO with GO or rGO.

The separation and capture of CO2 have become an urgent and important agenda because of the CO2-induced global warming and the requirement of industrial products. Membrane-based technologies have proven to be a promising alternative for CO2 separations. To make the gas-separation membrane process more competitive, productive membrane with high gas permeability and high selectivity is crucial. Herein, we developed new cellulose triacetate (CTA) and cellulose diacetate (CDA) blended membranes for CO2 separations. The CTA and CDA blends were chosen because they have similar chemical structures, good separation performance, and its economical and green nature. The best position in Robeson’s upper bound curve at 5 bar was obtained with the membrane containing 80 wt.% CTA and 20 wt.% CDA, which shows the CO2 permeability of 17.32 barrer and CO2/CH4 selectivity of 18.55. The membrane exhibits 98% enhancement in CO2/CH4 selectivity compared to neat membrane with only a slight reduction in CO2 permeability. The optimal membrane displays a plasticization pressure of 10.48 bar. The newly developed blended membranes show great potential for CO2 separations in the natural gas industry.

Underwater Optical Communication (UWOC) systems are attractive to researchers due to their ability of low power consumption, less complexity, high data rates, and covert communication. Various half-duplex (HD) UWOC systems has been proposed in this regard, but due to half-duplex characteristics, these systems have failed to improve the high throughput gain, high power efficiency and high data rates etc. Hence, we provided a review of different Full-Duplex UWOC systems using different light sources, with respect to transmission range, operational power, data rate, wavelength, and different underwater communication mediums. We observed that these FD systems have improved the communication range as well as data transfer rates, while implementing different light sources (i.e. lasers, avalanche photo diodes (APD), green and blue LEDs and lasers) in their transceivers. However, we pointed out that power inefficiency is a major issue faced by FD-UWOC systems. We also presented BER comparison of different FD-UWOC systems, implementing different modulations schemes, and pointed out that FD UWOC systems implementing un-coded 8PPM and BPSK outperformed. Finally, we concluded the paper and also highlighted some future directions for the FD-UWOC systems, and hope that our review can provide a platform for future research in the targeted area.

The existing half-duplex medium access control protocols take longer time to transmit and receive successful data packets, due to longer propagation delays. Therefore, we proposed an Enhanced Full-Duplex Medium Access Control protocol for the underwater acoustic network. The proposed protocol increases throughputs by decreasing the time for successful data transmission. The proposed protocol sets a backoff timer to access the transmission opportunity by transmitting the ID based RTS control packet to the target destination node. The target destination sends back the CTS control packet containing the data transmission and ID information, then both immediately exchange the data with each other, consuming less transmission time while performing FD communication. We evaluate the performance of the proposed protocol with respect to increase in number of underwater sensor nodes and payload size. Simulation results proved that the proposed protocol significantly increased the throughputs, compared to the existing convention medium access control protocols.

Burning velocity of different chemicals is estimated using a model from mixed population considering inverted Kumaraswamy (IKum) distribution for component parts. Two estimation techniques maximum likelihood estimation (MLE) and Bayesian analysis are applied for estimation purposes. BEs of a mixture model are obtained using gamma, inverse beta prior, and uniform prior distribution with two loss functions. Hyperparameters are determined through the empirical Bayesian method. An extensive simulation study is also a part of the study which is used to foresee the characteristics of the presented model. Application of the IKum mixture model is presented through a real dataset. We observed from the results that Linex loss performed better than squared error loss as it resulted in lower risks. And similarly gamma prior is preferred over other priors.

Environmental pollution emanating from rapid industrialization has been considered a worldwide concern in recent years. Therefore, the scientific community is developing various kinds of new materials and techniques to minimize environmental problems. In this regard, aerogels have drawn much interest for the scientific community because of its extraordinary properties for various advanced applications, such as catalytic and energy storage devices. In this book chapter, fundamental synthesis method for preparing aerogel and its composites with metal and metal oxide has been reviewed. Moreover, properties of these aerogels can be further improved with graphene and its derivatives. Therefore, the composites of metal oxides and other inorganic materials with graphene, reduced graphene oxide, and graphene oxide have been reviewed. Water pollution is a major concern for the various countries. Different methods such as chemical oxidation process, distillation, membrane filtration, absorption, and photocatalytic are in practice to treat wastewater. However, the photocatalytic process is being considered an economical and efficient method to remove water pollutants. Therefore, the role of aerogels to cure the environmental issue by photocatalyst technique was also studied. In short, aerogels found attractive to degrade the various detrimental dyes such as methylene blue, rhodamine B, methyl orange, and congo red, etc.

The use of membrane technology in natural gas sweetening process has grown rapidly in recent years compared to other traditional purification processes. Carbon dioxide (CO2) is the main culprit of greenhouse gases produced through the combustion of fossil fuel. In this chapter, various principles and mechanisms of gas separations on the basis of solubility and diffusion are systematically reviewed. Furthermore, the development and performance of various polymeric and inorganic materials in light of the recent challenges, advantages, and disadvantages for natural gas purification are described. Development of mixed matrix membrane for natural gas purification is one of the potential solutions for the use of expensive, brittle, and highly selective inorganic materials with low cost and stable polymers. At the end of this chapter, an attempt is also made to show the research development and future direction of natural gas purification process through highly selective membrane materials. The potential of the hybrid process for natural gas purification is more advantageous and economical compared to a single membrane process.

Artificial intelligence now days are mainly dependent on deep learning techniques as it is rapidly growing and capable to outperform other approaches and even human at various problems. Intelligently utilizing resources that meets the growing need of demanding services as well as user behavior is the future of wireless communication systems. Autonomous learning of wireless environment at run time by reconfiguring its operating mode that maximize its utility, cognitive radio (CR) can be programmed and configured dynamically and their utility maximization inside a building is a challenging task. Re-configurability and perception are the key features of cognitive radio while latest machine learning techniques like deep learning is used for system adaptation. In this paper an adaptive model to enhanced cognitive radio utilization to be maximized is proposed, that is, Particle swarm optimization (PSO) in combination with Gradient-method and intends to maximize the utility of CR. For this purpose the primary objective is allocation of optimum powers to base stations (BSs), which is achieved in an iterative manner keeping in view power constraints. A novel Distributed power PSOGradient Algorithm (DPPGA) is introduced, which assures utility maximization under network power constraints. The information regarding utility and interference of an individual BS is available to all of BSs, which is a key parameter, exploited in the proposed algorithm. Simulations are carried out by considering different scenarios and results are compared with existing algorithms. The performance of proposed algorithm is remarkable.

Sea surface temperature (SST) is a critical oceanic parameter used in most of the statistical and dynamic prediction models. In association with monsoon cycle, the SST exhibits large variability in the northwestern Indian Ocean both in space and time. The present study investigates the intraseasonal variability of SST influenced by the monsoon cycle in the Sea of Oman and the Arabian Sea regions by examination of Argo datasets from 2004–2019. Significant variability is observed in the SST amplitude during the summer monsoon, where minimum value reaches 26.8°C in August in the central Arabian Sea and above 32°C in July in the Sea of Oman region. Our analysis results show that SST amplitudes are always high in the Arabian Sea regions during the transition periods and low during the summer monsoon. The lower amplitude of SST during the summer monsoon indicates strong winds forcing in the Arabian Sea regions as opposed to the Sea of Oman region where SST amplitudes always large. Our analysis results, based on Argo datasets, might be equally important for the air-sea interaction study and statistical dynamic models to predict the extreme weather events in the tropical Indian Ocean.

Due to large spectral efficiency and low power consumption, the Massive Multiple-Input-Multiple-Output (MIMO) became a promising technology for the 5G system. However, pilot contamination (PC) limits the performance of massive MIMO systems. Therefore, two pilot scheduling schemes (i.e., Fractional Pilot Reuse (FPR) and asynchronous fractional pilot scheduling scheme (AFPS)) are proposed, which significantly mitigated the PC in the uplink time division duplex (TDD) massive MIMO system. In the FPR scheme, all the users are distributed into the central cell and edge cell users depending upon their signal to interference plus noise ratio (SINR). Further, the capacity of central and edge users is derived in terms of sum-rate, and the ideal number of the pilot is calculated which significantly maximized the sum rate. In the proposed AFPS scheme, the users are grouped into central users and edge users depending upon the interference they receive. The central users are assigned the same set of pilots because these users are less affected by interference, while the edge users are assigned the orthogonal pilots because these users are severely affected by interference. Consequently, the pilot overhead is reduced and inter-cell interference (ICI) is minimized. Further, results verify that the proposed schemes outperform the previous proposed traditional schemes, in terms of improved sum rates.

This article investigate the performance of various sophisticated channel coding and transmission schemes for achieving reliable transmission of H.264/AVC compressed video. The performance of the proposed schemes, namely Non-Convergent Coding (NCC), Non-Convergent Coding assisted with Differential Space Time Spreading (DSTS) and Sphere Packing (SP) modulation (NCDSTS-SP) and Convergent Coding assisted with Differential Space Time Spreading (DSTS) and Sphere Packing (SP) modulation CDSTS-SP, is analyzed using Bit Error Ratio (BER) and Peak Signal to Noise Ratio (PSNR) performance of the transmitted video stream. Channel codes incorporate artificial residual redundancy in the coded information bits, which is advantageous in the decoder side to overcome error effects and to accomplish the lowest desired BER. To cope with the very high compression ratio efficiency of the H.264/AVC video codec, our proposed system induces artificial redundancy in the compressed video bit-stream with the aid of Over Complete Mapping (OCM) and Recursive Systematic Convolution (RSC) channel codes, in order to improve the error resilience of the transmitted stream. Furthermore, overall BER reduction and improvement in objective quality performance is achieved using sophisticated transceiver design consisting of the advanced Sphere Packing (SP) modulation technique assisted by Differential Space Time Spreading (DSTS). The performance of the Iterative Soft Bit Source Decoding (SBSD) and channel decoding is analyzed using various error protection setups by allocating persistently constant overall bit rate budget. Additionally, the Iterative behavior of the SBSD assisted Recursive Systematic Convolution (RSC) code is analyzed with the aid of Extrinsic Information Transfer (EXIT) Chart. Moreover, it is observed from the experimental results that the sophisticated system design of CDSTS-SP outperforms its counterpart in terms of BER and PSNR. More specifically NCDSTS-SP results in PSNR gain of 6 dB and CDSTS-SP results in PSNR gain of 28 dB for Eb/N0 value of 10 dB, with reference to bench marker system design of NCC.

There will be a dearth of electrical energy in the prospective world due to exponential increase in electrical energy demand of rapidly growing world population. With the development of internet-of-things (IoT), more smart devices will be integrated into residential buildings in smart cities that actively participate in electricity market via demand response (DR) programs to efficiently manage energy in order to meet this increasing energy demand. Thus, with this incitement, an energy management strategy using price-based DR program is developed for IoT-enabled residential buildings. We propose a wind-driven bacterial foraging algorithm (WBFA), which is a hybrid of wind-driven optimization (WDO) and bacterial foraging optimization (BFO) algorithms. Subsequently, we devised a strategy based on our proposed WBFA to systematically manage the power usage of IoT-enabled residential building smart appliances by scheduling to alleviate peak-to-average ratio (PAR), minimize cost of electricity, and maximize user comfort (UC). This increases effective energy utilization, which in turn increases the sustainability of IoT-enabled residential buildings in smart cities. The WBFA-based strategy automatically responds to price-based DR programs to combat the major problem of the DR programs, which is the limitation of consumer&rsquo, s knowledge to respond upon receiving DR signals. To endorse productiveness and effectiveness of the proposed WBFA-based strategy, substantial simulations are carried out. Furthermore, the proposed WBFA-based strategy is compared with benchmark strategies including binary particle swarm optimization (BPSO) algorithm, genetic algorithm (GA), genetic wind driven optimization (GWDO) algorithm, and genetic binary particle swarm optimization (GBPSO) algorithm in terms of energy consumption, cost of electricity, PAR, and UC. Simulation results show that the proposed WBFA-based strategy outperforms the benchmark strategies in terms of performance metrics.

The traditional free-space and half-space analysis method ignore the reflection of the upper and lower boundaries of shallow sea and are not suitable for analyzing shallow sea problems especially at high frequency. Hence, a method combining ray theory and wave superposition theory is proposed in this paper to predict the high-frequency radiated acoustic field in shallow water. The proposed method takes into account the effect of channel boundaries on the acoustic field and has good adaptability to complex channel environments and accuracy of the calculated acoustic field.

Despite the recent advancement in graphene oxide (GO) as a host material in energy and environmental sectors, its composite thin films with metal oxides such as nickel oxide (NiO) and its optical, structural, chemical state, and photocatalytic activities have been poorly explored. Herein, we have reported the GO/NiO thin films preparation by a combination of chemical and physical deposition techniques (i.e. spin coating followed by DC/RF sputtering). The as-prepared composites thin films were characterised using Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy scanning electron microscopy, and atomic force microscopy. The surface topography confirmed the uniform deposition of NiO over thin films of GO. The XPS results showed the formation of NiC along with the partial reduction in GO into graphene with their existing four constituents, i.e. NiO, NiC, GO, in the thin film composites. The classical plasmon, Wemple and Didomenico model, was first time applied for GO/NiO to compute energy loss functions, and dispersion energy parameters. The theoretical calculated values for the deposited GO/NiO thin films were found to be in very close agreement to the standard classical plasmon values. The change in spin orbital movement of Ni is considered due to the interaction between its nanoparticles and basal planes of GO. Thin films applied for the photodegradation of recalcitrant organic pollutant 2-chlorophenol (2-CP) revealed the dependence of photocatalytic efficiency on particle size and also on the interaction of GO with NiO rather than the ratio of NiO and GO in the films.

In this work, the X-ray Photoelectron Spectroscopy (XPS) technique is utilized to analyze the surface chemical composition of particulate matter (PM) which was collected from various locations at Jeddah, Saudi Arabia. The main elements found on the surface of PM are carbon (C), oxygen (O) and silicon (Si) with combined percentage of 89.4–94.9 while traces of nitrogen (N), calcium (Ca), aluminum (Al), sodium (Na), chlorine (Cl), manganese (Mg), and sulfur (S) were also present. The analyzed XPS chemical state of C, O and Si was further used to determine their bonding with other elements occurring over the surface of PM. Carbon was found in the form of carbides (18.86%), fluorides (2.39%) and carbonates (78.75%); oxygen was observed as oxides (21.05%) and hydroxides (73.42%) of other metals; and silicon was detected as silicones (12.16%), nitrides (82.53%) and silicates (5.25%). The particle size of a PM is also of great concern for health issues, and thus has been investigated by the Field Emission Scanning Electron Microscope (FESEM). The Energy Dispersive X-ray Spectroscopy (EDS) was employed for cross verification of detected elements by XPS.

Graphene was discovered in 2004 and has attracted intensive interests because of its unique mechanical, electric, thermal, optical, and structural properties, which makes graphene a potential candidate for various applications. Graphene is being used as a composite or filler material with metals, metal oxides, and polymers for potential advanced applications in solar cells, lithium-ion batteries, photocatalysis and sensing. These applications depend upon the distinctive properties of graphene, which in turn depend on the adopted synthetic approach. This article reviews the recent developments in synthesis of graphene and related composite materials. The synthesis of graphene through exfoliation, epitaxial growth and direct growth via carbon source, and modification approaches by covalent and noncovalent methodologies are discussed. Graphene-based metal and metal oxide composites for the purification of wastewater using photolytic process are also presented.

Carbon dioxide (CO2) is the main culprit of greenhouse gases produced mainly via the combustion of fossil fuel. This paper reviewed the performance of emerging dual-layer hollow fiber membrane, its fabrication via co-extrusion process, improvement, challenges, spinning parameters, advantages and disadvantages in comparison to single-layer hollow fiber membrane for natural gas purification. Development of delamination-free dual-layer hollow fibers via co-extrusion and phase inversion technology is one of the potential solutions for the use of expensive and brittle polymers for the outer selective layer and low cost polymers with high thermal and mechanical properties for the porous inner layer.

Thin film is a subject of great interest for energy and environmental applications. Graphene oxide (GO) in this regard can play a vital role in thin film technology because of its extraordinary optoelectronics and environmentally friendly characteristics. Despite the fast development in the GO based material, there are very few reports on optoelectronics and antibacterial activity of GO thin films. Herein, GO thin films of different concentrations have been deposited on glass substrate by spin coating technique. The optical and dielectric properties of GO thin films were determined by the UV–visible technique. Crystalline nature, grain sizes, dislocation density, and lattice strain were examined through X-ray diffraction. The possible change in the π-π* and n-π* electronic transition and the band gap evaluations of GO thin films were also calculated. Raman spectroscopy was applied to check the quality and defects linked to sp2 breathing modes of GO thin films. Surface chemical state and ratio of C C, C O, O C OH, O C, and ( O) O were investigated through X-rays photoelectron spectroscopy. GO thin films were also subjected for antibacterial activity tests towards Bacillus cereus and Serratia marcescens and significantly inhibition of bacterial growth in both solid and liquid media was observed. The results emphasise the potential uses of GO thin films in optoelectronics, environmental, and medical device coating for protection against various infectious agents.

A new micron-sized leaf- two-dimensional (2D) structured zeolitic imidazolate framework (ZIF-L) and nano-sized ZIF-8 were successfully synthesised in aqueous basic solution at room temperature with the same molar ratio of reagents (Zn+ 2/Hmim = 8). Both ZIFs have attracted tremendous research interest due to their wide applications including absorption, separation, and catalysis. This phase and morphology change could be tailored by changing the concentration of base-type additive triethylamine (TEA). Also, this morphology change from 2D (ZIF-L) to three-dimensional (3D) (ZIF-8) was observed by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), attenuated total reflectance infrared (ATR-IR) spectroscopy analysis, and surface area and pore textural properties using micromeritics gas adsorption analyser. The total amount of basic sites and carbon dioxide (CO2) desorption capacity were also calculated using CO2 temperature-programmed desorption (CO2-TPD) technique. Furthermore, TEA/total mole ratio of 0.0006 was proved as transition loading between two phases. Also, the particle and crystal size of samples decreased with increasing TEA/total mole ratio. The smallest ZIF-L and ZIF-8 particles obtained were 1.6 μm and 177 nm, respectively that showed excellent thermal stability. The basicity and uptakes of CO2 improved proportionally with TEA and followed this order: ZIF-8 > ZIF-L. This study provides some new insights into zeolitic imidazolate framework by controlling crystal growth and morphology.

The recently emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a significant and topmost global health challenge of today. SARS-CoV-2 can propagate through several direct or indirect means resulting in its exponential spread in short times. Consequently, finding new research based real-world and feasible solutions to interrupt the spread of pathogenic microorganisms is indispensable. It has been established that this virus can survive on a variety of available surfaces ranging from a few hours to a few days, which has increased the risk of COVID-19 spread to large populations. Currently, available surface disinfectant chemicals provide only a temporary solution and are not recommended to be used in the long run due to their toxicity and irritation. Apart from the urgent development of vaccine and antiviral drugs, there is also a need to design and develop surface disinfectant antiviral coatings for long-term applications even for new variants. The unique physicochemical properties of graphene-based nanomaterials (GBNs) have been widely investigated for antimicrobial applications. However, the research work for their use in antimicrobial surface coatings is minimal. This perspective enlightens the scope of using GBNs as antimicrobial/antiviral surface coatings to reduce the spread of transmittable microorganisms, precisely, SARS-CoV-2. This study attempts to demonstrate the synergistic effect of GBNs and metallic nanoparticles (MNPs), for their potential antiviral applications in the development of surface disinfectant coatings. Some proposed mechanisms for the antiviral activity of the graphene family against SARS-CoV-2 has also been explained. It is anticipated that this study will potentially lead to new insights and future trends to develop a framework for further investigation on this research area of pivotal importance to minimize the transmission of current and any future viral outbreaks.

Palm oil fuel ash (POFA) is a waste material generated in large quantities by palm oil industry worldwide. To avoid the rising disposal costs and environmental issues, its positive and cost-effective utilization is the urgent requirement. An economical, single-step, and green chemical method has been adopted in this study to convert as received waste byproduct, POFA, from oil palm mills to produce precious "POFA derived graphene (PDG) nanosheets." The results analyses from different latest instrumental techniques like Raman, High-resolution transmission electron microscopy (HRTEM) and Atomic force microscopy (AFM) confirmed the successful synthesis of 1–8 layer PDG nanosheets with high yield (> 25 wt%). Parameters like temperature, the ratio of KOH: POFA, and reaction time were optimized to get the maximum yield and removal of all inorganic impurities up to

Hollow fiber membrane (HFM) technology has received significant attention due to its broad range separation and purification applications in the industry. In the current study, we applied bibliometric analysis to evaluate the global research trends on key applications of HFMs by evaluating the global publication outputs. Results obtained from 5626 published articles (1970–2020) from the Scopus database were further manipulated using VOSviewer software through cartography analysis. The study emphasizes the performance of most influential annual publications covering mainstream journals, leading countries, institutions, leading authors and author’s keywords, as well as future research trends. The study found that 62% of the global HFM publications were contributed by China, USA, Singapore, Japan and Malaysia, followed by 77 other countries. This study will stimulate the researchers by showing the future-minded research directions when they select new research areas, particularly in those related to water treatment, biomedical and gas separation applications of HFM.

Phenol and its derivatives are among the dangerous pollutants usually found in the wastewater of petrochemical and pharmaceutical industries. Photodegradation is one of the most promising techniques to treat phenol-polluted wastewater. The lack of reusability of the photocatalyst and their high agglomeration tendency have reduced its stability and efficiency. To address these limitations, a binary nanocomposite of Fe3O4@SiO2 was synthesized in this study to be used as an active photocatalyst for the photodegradation of phenol under UV irradiation. Numerous physicochemical characterizations were performed to study the morphology, crystallinity, thermal stability of the prepared nanocomposite. These techniques confirmed the effective fusion of the two entities in the newly formed nanocomposite. The efficiency of the photocatalysts was steadily enhanced over the period investigated in this study. The phenol degradation efficacy of 84% was accomplished using Fe3O4@SiO2 composite, which was higher as compared to that of single Fe3O4 (59%). The newly prepared materials can be effectively recycled by facile magnetic separation method.

Biogas upgrading is a widely studied and discussed topic and its utilisation as a natural gas substitute has gained a significant attention in recent years. The production of biomethane provides a versatile application in both heat and power generation and as a vehicular fuel. This paper systematically reviews the state of the art of biogas upgrading technologies with upgrading efficiency, methane (CH 4 ) loss, environmental effect, development and commercialisation, and challenges in terms of energy consumption and economic assessment. The market situation for biogas upgrading has changed rapidly in recent years, making the membrane separation gets significant market share with traditional biogas upgrading technologies. In addition, the potential utilisation of biogas, efficient conversion into bio-compressed natural gas (bio-CNG), and storage systems are investigated in depth. Two storing systems for bio-CNG at filling stations, namely buffer and cascade storage systems are used. The best storage system should be selected on the basis of the advantages of both systems. Also, the fuel economy and mass emissions for bio-CNG and CNG filled vehicles are studied. There is the same fuel economy and less carbon dioxide (CO 2 ) emission for bio-CNG. Based on the results of comparisons between the technical features of upgrading technologies, various specific requirements for biogas utilisation and the relevant investment, and operating and maintenance costs, future recommendations are made for biogas upgrading.

Objectives: Rate controlis a very important factor in video coding. In video communications, rate control must ensure that the coded bit stream can be transmitted effectively and make full use of the narrow bandwidth. For various sequences the impact of rate control methods is examined and algorithm for rate controller for verification model version 8.0 for moving picture expert group-4 is defined. Methods/Statistical Analysis: In this work, Rate control analysis for H.263, MPEG-4 is fulfilled. For Rate control analysis of MPEG-4 test model, verification of model version 8.0 is followd. For H.263 Test Model Number 5 (TMN5), Test Model Number 8 (TMN8) and Test Model Number 12 (TMN12) are used. For various sequences is notice that the bit rate is varied and coefficient of correlation and peak signal to noise ratio is analyzed. Findings: In this work, Rate control analysis for H.263, MPEG-4 is fulfilled. Rate Control algorithm for MPEG-4 is developed. Influence of different rate control methods is analyzed and try to find which rate control methods i.e. C-1, C-2 and C-3 is suitable for which type of sequence specifications. Applications/Improvements: The performance evaluation is put forward for consideration in this work will activate the user analyzing experimental results of various rate control methods and how optimum rate-distortion will fulfilled for MPEG-4&H.263 video codec attained.

Herein, we report the synthesis of few-layered graphene oxide (GO), reduced graphene oxide (rGO), and rGO/ZnO thin films on a glass substrate by the combination of spin coating, low temperature thermal annealing, and radio frequency (RF) sputtering. A spectroscopic approach was applied for the very first time to calculate the optical and dielectric properties of GO thin films. The GO thin film was characterised for structural, optical, morphological, and surface chemical state composition properties by X-ray diffraction, UV-visible spectroscopy, atomic force microscopy, field emission scanning electron microscopy, and X-ray photoelectron microscopy. The chemical state analysis of O1s and C1s spectra evidently proved the successful reduction of GO at 200–300 °C. The change in grain size, lattice strain, and dislocation density was studied after the reduction of GO to rGO, and the band gap analysis was performed through Tauc plot relation. The optical conductivity of the GO films was estimated by the UV technique. Moreover, the dielectric constant and dielectric loss of GO and rGO thin films were also studied, and the samples annealed at high temperature showed comparatively low loss. Due to the high conductivity and low band gap of few-layered rGO, its composite with RF-sputtered ZnO (rGO/ZnO) was studied for its ability to photocatalytically degrade 2-chlorophenol.

In this article, Maximum likelihood estimation (MLE) and Bayesian estimation for Rayleigh distribution using progressive type-II censoring in the presence of outliers is considered. Inverse Gamma prior and Jeffreys prior are used for Bayesian estimation. Squared error loss function (SELF), precautionary loss function (PLF) and K-loss function (KLF) are used for obtaining the expressions of Bayes estimators and posterior risks. Credible intervals are also derived. A simulation study is presented to discuss the behavior of Bayes estimators. Applicability of the undertaken study is highlighted using three real data sets.

This paper addresses selective coordination of protections in Low Voltage critical power electrical installations. We describe a digital interlock system, developed for MV/LV power distribution in critical power facilities, with the presence of multiple power generators, including the case of meshed distribution networks. A ship is considered as a case study, with MV/LV stations operated as a closed loop, and about 20MW total loads. Ethernet links are used for connection between protective devices in each switchboard. A redundant optical fiber link based on a fast-recovery ring structure is used for connection among switchboards. This architecture allows seamless data exchange between Medium Voltage protection relays and Low Voltage circuit breakers placed in the same or in different locations in the plant. Selective interlocking is ensured even in the case one of the optical links is lost. Immunity to EM noise is also improved. Before deployment in a real installation, the designed system has been reproduced in a Hardware-In-the-Loop environment, which allows the simulation of test cases including electrical faults in each location of the plant, failure of communication devices and links, or a combination of them at different times.

High operational complexity and computational time degrades the performance of already existing Amplify-and-Forward (AF) based two time slots algorithms in the literature, used for cooperative networks, and has several issues related to bit error rate, computation time etc. Consequently, the Operational Complexity Reduction Algorithm (OCRA) for single relay cooperative network has been proposed. The error probability of bits received is derived using the harmonic and geometric means, initial value theorem, and probability density function at zero. Moreover, the proposed algorithm is evaluated with the previous proposed algorithm. The OCRA demonstrated low Bit Error Rate (BER) and high BER-Gain values, with the increase in SNR values, at particular fading conditions. The proposed algorithm demonstrated less computational time and low operational complexity, as compared to previous proposed algorithm.

Long term goals need to be set to promote the country’s circular economy (CE) as well as the cleaner environment by recycling waste materials into useful products. In pursuit of controlling environmental threats of carbon-based industrial wastes, different preprocessing techniques for their conversion into other value-added materials are being put in use. This review targets the purposeful utilization of massive amount of palm oil fuel ash (POFA), generated as a waste from power plants of palm oil processing mills in the major palm oil-producing countries. Currently, unrestrained disposal of POFA captures not only precious land but also creates environmental threats and health-related issues. Present work is an attempt to establish a sustainable cleaner production (SCP) system instead of unmanaged POFA disposal. Major palm oil producer countries should address the emerging issues of POFA related unsafe environment, energy consumption and landfill spaces by adopting reuse, reduce and recycle principles. Technically, this review also focuses on the use of POFA as a promising cementitious material in concrete production. It also maps the importance of POFA in concrete production as a cement replacement by presenting various state-of-the-art chemical reactions, mode of action of POFA for its pozzolanic reactivity in cement compositions and associated technical, environmental, and economic benefits. This will provide an alternative option and a sustainable solution for the global construction industry. It is conclusively evident from an extensive literature survey of 463 published results from last 26 years that POFA can be effectively used in concrete production to replace cement without compromising on its strength, performance, and durability. Based on the till that research work on POFA applications in the cement industry and other multiple areas, a circular economic model has been presented to support the concept of zero waste and SCP. It will stimulate the technical persons and decision-makers to make policies and strategies that can spotlight the effective use of POFA in multiple applications, primarily focusing on concrete production not only for curtailing the land and water pollution but also acquiring economic benefits.

Underwater wireless communication has gained a great deal of attention in the last couple of decades because of its applications in the military, industrial, and monitoring sectors. Despite the extreme physical and MAC layer difficulties, acoustics are used for various applications among the various modes of underwater communication technologies used. While significant research efforts have been made to address these issues, the bottleneck remains in achieving high bandwidth, high throughputs, and data rate. Researchers have begun to look into full duplex (FD) implementation to improve bandwidth efficiency and increase data rate and throughput. Users can send and receive data simultaneously over the FD links, maximizing bandwidth utilization and increasing throughput. As a result, we thoroughly reviewed various FD physical layered UWAC systems and MAC layered protocols for underwater communication. The various problems that the aforementioned systems and protocols have faced, as well as the solutions suggested in previous works to solve each problem, are also highlighted. Various metrics are used to compare the performance of various physical layered FD systems and FD MAC protocols. We also explore some of the open research questions in these FD-physical layered and MAC layered protocols, as well as future research directions. Based on ample information, we suggest a cross-layered architecture based on various IBFD-SI cancellations, DA-CSMA, and FD-MAC protocols. This review provides a broad view of the current FD physical and MAC layered protocols based on acoustic communication, as well as recommendations.

The low identification rate of the Orthogonal frequency division multiplexing (OFDM) based subcarrier modulation in underwater acoustic multipath channel is an important issue. Therefore, we proposed a novel Expectation Maximization-Block-Quasi Hybrid Likelihood Ratio Test (EM-Block-QHLRT) method which effectively improved the identification rate while using the blind channel impulse response (CIR) estimation and likelihood. Initially, CIR is obtained by using clustering, and then the CIR is updated iteratively by EM-Block method. Further, the subcarrier modulation is identified using QHLRT. The influence of iteration times, the length of symbol and influence of the number of blocks in EM are analyzed by using extensive simulation. The identification rate of subcarrier modulation of binary phase shift keying (BPSK), QPSK, 8PSK and 16QAM are presented using different signal noise ratio (SNR). In addition, the identification rate of subcarrier modulation based on Average Likelihood Rate Test (ALRT) as well as QHLRT with EM are compared. Simulation results showed that the identification rate of the proposed EM-Block-QHLRT method can reach to more than 90% when SNR is higher than 5 dB. Finally, the performance of the proposed EM-Block-QHLRT method is verified using sea trial data.

A combined Finite Element Method with Normal Mode (FEM-NM) is proposed for calculation of the acoustic field radiated by a three-dimensional structural source in shallow water. The FEM is used to calculate the near range acoustic field, then the modes expansion at the vertical and azimuthal direction is performed at a certain coupling range. Hence, the true three-dimensional acoustic field at any range is obtained rapidly by the NM theory. The numerical examples show the efficiency and accuracy of this method. The coupling range and the truncation of the vertical modes hardly affect the far field results.

In the recent past, a significant increase has been observed in the use of underwater wireless sensor networks for aquatic applications. However, underwater wireless sensor networks face several challenges including large propagation delays, high mobility, limited bandwidth, three-dimensional deployments, expensive manufacturing, and energy constraints. It is crucial for underwater wireless sensor networks to mitigate all these limitations primarily caused by the harsh underwater environment. To address some of the pertinent challenges, adaptive hop-by-hop cone vector-based forwarding routing protocol is proposed in this article which is based on the adaptive hop-by-hop vector-based forwarding. The novelty of adaptive hop-by-hop cone vector-based forwarding includes increasing the transmission reliability in sparse sensor regions by changing the base angle of the cone according to the network structure. The number of duplicate packets and end-to-end delay is also reduced because of the reduced base angle and a smart selection criterion for the potential forwarder node. The proposed routing protocol adaptively tunes the height and opening of the cone based on the network structure to effectively improve the performance of the network. Conclusively, this approach significantly reduces energy tax, end-to-end delay, and packet delivery ratio.

Mixed matrix membranes (MMMs) have received worldwide attention for natural gas purification due to their superior performance in terms of permeability and selectivity. The zeolitic imidazole framework-8 (ZIF-8) blended polysulfone (PSf) membranes have been fabricated for natural gas purification. ZIF-8 was selected due to its low cost, remarkable thermal and chemical stabilities, and tunable microporous structure. The neat PSf hollow fiber membrane and mixed matrix hollow fiber membranes incorporated with the various ZIF-8 loadings up to 1.25% were fabricated. The prepared membranes were evaluated using field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and gas separation performance. The low loading of ZIF-8 nanoparticles to the MMM improved thermal stability and glass transition temperature and yielded low surface roughness. MMMs were tested using pure gases with a significant improvement of 36% in CO2 permeability and 28% in CO2/CH4 selectivity compared to the neat membrane. However, the high ZIF-8 loading reduced the separation performances. Moreover, CO2/CH4 selectivity decreased at elevated pressure (8 and 10 bar) due to CO2-induced plasticization. Previously, the incorporation of ZIF-8 particles has primarily been subjected to the fabrication of flat sheet membranes, whereas this work focused on hollow fiber membranes which are rarely investigated. Hence, the promising results obtained at low feed pressure in this study demonstrated the potential of ZIF-8 based hollow fiber membrane for natural gas purification.