A series of lead-free [(Bi0.5Na0.5)0.94 Ba0.06](1-x)LaxTiO3 (abbreviated as BNBTLa) with x = 0, 0.01, 0.02, 0.03 and 0.04 piezoelectric compound were synthesized using solid solution method. The structure, electromechanical and electrical properties were studied in detail. X-ray diffraction (XRD) analysis confirmed a rhombohedral symmetry for undoped, while La-doped compositions displayed a pseudocubic phase. The field-emission scanning electron microscopy (FE-SEM) of BNBTLa compound presented a decrease in grain size from 1.01 μm (x = 0), to 0.82 μm (x = 0.04). The ferroelectric-relaxor transition temperature (TF-R) shifted down to room temperature and the diffusivity (γ) values ranged between 1 and 2. The P-E hysteresis loops profile became slimmer with the doping of La contents with reduction in remnant polarization Pr and coercive field (EC). A normalized strain of 485 pm/V was found for the sample x = 0.03. These characteristics of the BNBTLa system signified a transition from the ferroelectric to the relaxor phase. Therefore, the prepared ceramics offered extendable availability for environmental friendly capacitors, sensors and actuators.

Co-based alloys are promising to offer high-temperature corrosion resistance under extreme environmental conditions. Here, we report a novel approach that exploits the characteristics of the oxidation scale by making the specimens ground at three different levels to compare the effects of surface roughness in the presence and absence of external pressure. At a constant pressure of 2.5 MPa, the influence of surface roughness on the oxidation behaviour at an elevated temperature of 1050°C for 430 h has been investigated via scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer and X-ray diffraction. The results have revealed that for rough surfaces the thickness of the oxide scale with Ra = 76.0 nm is significantly higher compared to a smooth surface with Ra = 13.0 nm. Furthermore, the oxide scale on the rough surface has some micro defects and protrusion compared to smooth surfaces. Besides that, under the applied external pressure and surface roughness, more pressure- and roughness-induced cracks and discontinuity have been observed on the oxide scale.

The investigation of various factors effecting the Lead (Pb) diffusion in phosphate minerals such as apatite is still challenging in the interpretation of (U-Th)/Pb geochronology. For (U-Th)/Pb system, apatite minerals have closure temperatures in the range of 375 to 600 degrees C and therefore can be used for the investigation of mid temperature thermochronological and/or petrochronological questions i.e., the reconstruction of thermal events in Earth's crust. There is still uncertainty whether Pb diffusion in apatite is characterized by thermally activated volume and/or anisotropic diffusion profiles or is instead impacted by novel growth processes and recrystallization (chemical substitutions). As the apatite structure support extensive compositional variability, including partial or total substitution of both the cationic and anionic sites and forms solid solutions therefore, it necessitates a thorough examination of these effects and anisotropy on Pb diffusivity and (U-Th)/Pb geochronometric system. For this, a multi-scale study is carried out to examine the effects of chemical composition, anisotropy, and growth structure on the diffusion of Pb in order to better understand the behaviour of Pb diffusion in apatite. This study employed computational techniques like Density Functional Theory (DFT) and Transition State Theory (TST) at the atomic level and integrates it with the Kinetic Monte Carlo (KMC) simulations at the macroscopic level. Models of this study shows that Pb diffusion is completely anisotropic along the preferred z-axis or [001] direction and Pb readily escapes faster from Na-substituted apatite when compared to pure F-apatite and Cl-substituted apatite. Because of this anisotropy and chemical substitutions, Pb diffusivity in apatite either increases by opening of diffusion channels or decreases by blocking the diffusion channels depending on the site and type of chemical substitution. Further, in case of blocking effect the Pb diffusion occurs through workaround pathways and approaches towards the isotropic diffusion. For Na-substituted apatite, the impact of Na occupation on anisotropic Pb diffusion is significantly greater while in case of Cl-substituted apatite the Cl occupation mostly leads towards isotropic diffusion by opening the diffusion paths along other directions (mostly along the in-plane direction). Furthermore, the high closure temperatures (Tc) (e.g.,-1370 degrees C) of the modelled apatites (except the perfect Na-substituted apatite e.g.,-500 degrees C) of this study when compared to the Tc of Durango apatite obtained experimentally for the effective grain size of 100 mu m and cooling rates of 10 degrees C/Ma indicate that the effective closure temperature dominantly depends on the degree and types of chemical substitutions and play a crucial role for the closure or opening of Pb diffusion/loss in apatites.

Millimeter wave (mm-Wave) wireless communication systems require high gain antennas to overcome path loss effects and thereby enhance system coverage. This paper presents the design and analysis of an antenna array for high gain performance of future mm-wave 5G communication systems. The proposed antenna is based on planar microstrip technology and fabricated on 0.254 mm thick dielectric substrate (Rogers-5880) having a relative permittivity of 2.2 and loss tangent of 0.0009. The single radiating element used to construct the antenna array is a microstrip patch that has a configuration resembling a two-pronged fork. The single radiator has a realized gain of 7.6 dBi. To achieve the gain required by 5G base stations, a 64-element array antenna design is proposed which has a bore side gain of 21.2 dBi at 37.2 GHz. The 8 × 8, 8 × 16, and 8 × 32 antenna array designs described here were simulated and optimized using CST Microwave Studio, which is a 3D full-wave electromagnetic solver. The overall characteristics of the array in terms of reflection-coefficient and radiation patterns makes the proposed design suitable for mm-Wave 5G and other communication systems.

A first principle study was performed to investigate the electronic and thermostructural properties of the Ti 2 AlC MAX-phase using quasi-harmonic Debye approximation. The thermodynamical properties of Ti 2 AlC MAX-phase at various temperatures and pressure were calculated via the quasi-harmonic Debye approximation and explored the role of temperature and pressure on heat capacity, bulk modulus, thermal expansion coefficient, Debye temperature, enthalpy, entropy, and Gibbs free energy. Surprisingly, both the bulk modulus and Debye temperature was observed to drop with increase in temperature. However, a rise in both occurred as the pressure gradually builds up. This suggests that the heat capacity is influenced by pressure and temperature in opposing ways. The observation of increase in both heat capacities ( C p and C v ) due to increase in temperature infers an increase in the thermal velocity of the atoms. Consequently, the thermal velocity of the atoms decreases with a decrease in pressure which affects C p and C v , respectively. In addition, the Gibbs free energy slope increased at a little rate at constant pressure. These novel results possessing improved thermostructural properties could be useful for high-temperature fatigue-resistant applications specially in a gas turbine engine.

The growth of high-efficiency phase change material (PCM) nanocomposites with good heat conduction and substantial thermal capacity was of vital significance for practical matters in the sustainable utilization of energy. A novel leakage-proof n-heptadecane-graphene nanocomposite was prepared by a direct impregnation procedure from n-heptadacne as a PCM and nanographene as a skeleton. The creation of shape-stabilized nanocomposite was checked with X-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) spectroscopy. The scanning electron microscopy (SEM) analysis illustrated that the n-heptadecane and graphene had favourable compatibility and there was no phase separation and graphene accumulation. Thermal analysis showed that the shape-stabilized nanocomposite not only had a good phase transition enthalpy (101.7 J/g) and n-heptadecane content (45.6 %) but also possessed appropriate thermal stability. The heat conduction of the obtained mesoporous nanocomposite was up to 1.527 W/mK, with a growth of 808 % compared to pure n-heptadecane. Furthermore, the optimized nanocomposite held auspicious thermal reliability, being exposed to 400 thermal cycles. Moreover, the thermoregulation tests demonstrated that the gypsum boards containing optimized nanocomposite showed a slow heat release rate and improved the building temperature profile over only the gypsum board. By virtue of the combination of n-heptadecane and thermal conductive nanographene, the obtained engineered nanocomposite might be regarded as a smart material for energy-conserving and temperature regulation in buildings.

Data caching has emerged as a promising technique to handle growing data traffic and backhaul congestion of wireless networks. However, there is a concern regarding how and where to place contents to optimize data access by the users. Data caching can be exploited close to users by deploying cache entities at Small Base Stations (SBSs). In this approach, SBSs cache contents through the core network during off-peak traffic hours. Then, SBSs provide cached contents to content-demanding users during peak traffic hours with low latency. In this paper, we exploit the potential of data caching at the SBS level to minimize data access delay. We propose an intelligence-based data caching mechanism inspired by an artificial intelligence approach known as Reinforcement Learning (RL). Our proposed RL-based data caching mechanism is adaptive to dynamic learning and tracks network states to capture users’ diverse and varying data demands. Our proposed approach optimizes data caching at the SBS level by observing users’ data demands and locations to efficiently utilize the limited cache resources of SBS. Extensive simulations are performed to evaluate the performance of proposed caching mechanism based on various factors such as caching capacity, data library size, etc. The obtained results demonstrate that our proposed caching mechanism achieves 4% performance gain in terms of delay vs. contents, 3.5% performance gain in terms of delay vs. users, 2.6% performance gain in terms of delay vs. cache capacity, 18% performance gain in terms of percentage traffic offloading vs. popularity skewness (γ), and 6% performance gain in terms of backhaul saving vs. cache capacity.

We report the electronic and thermoelectric properties of electron- and hole-doped bulk-GaN and monolayer (ML)-GaN crystal structures using density functional theory and Boltzmann transport equations. In addition, we have studied the tuning of the band gap from the bulk to the ML which is expected to improve the thermoelectric properties of the ML-GaN. The negative formation energies show the thermodynamic stability of both bulk-GaN and ML-GaN. At the same time, there is no negative frequency in the phonon spectrum, which shows the dynamic stability of ML-GaN. The GGA (HSE)-calculated electronic band gap is 1.64 eV (3.25 eV), and 2.09 eV (3.85 eV) for the bulk-GaN and ML-GaN, respectively. Using the Phono3py code, it was found that, at room temperature, the $$\kappa _l$$ of ML-GaN along the [1 0 0] and [0 1 0] directions is 72.877 W/m-K and 20.984 W/m-K, respectively, which is much smaller than the $$\kappa _l$$ for bulk-GaN. Therefore, the figure-of-merit (ZT) predicted value is as high as 0.78 (0.98) for the electron- (hole-) doped bulk-GaN at room temperature. Furthermore, we established that reducing the dimensionality caused an increase (decrease) of the electronic conductivity (thermal conductivity). As a result, ZT significantly increased to 0.81 (1.19) for the electron- (hole-) doped ML-GaN at 800 K. The ZT  $$\ge 1$$ for a material indicates high applicability in thermoelectric device applications.

In this paper, a modified convex optimization technique is used for radiation pattern correction in a cylindrical-shaped conformal microstrip array antenna. The technique uses numerical simulations to optimize the amplitude and phase excitations, with the goal to decrease the Euclidean distance between the desired field pattern and the obtained (simulated/measured) field pattern while maintaining the main beam direction, null's location, and side lobe levels under control. Two prototypes of 1 × 4 and 2 × 4 conformal microstrip antenna array deformed from linear/planar structure to the prescribed cylindrical shape, with different radii of curvature, are studied to demonstrate the performance of the proposed technique. The proposed convex optimization model when applied to conformal antenna array possesses fast computing speed and high convergence accuracy for radiation pattern synthesis, which can be a valuable tool for engineering applications.

User Equipment (UE) is equipped with limited cache resources that can be utilized to offload data traffic through device-to-device (D2D) communications. Data caching at a UE level has the potential to significantly alleviate data traffic burden from the backhaul link. Moreover, in wireless networks, users exhibit mobility that poses serious challenges to successful data transmission via D2D communications due to intermittent connectivity among users. Users’ mobility can be exploited to efficiently cache contents by observing connectivity patterns among users. Therefore, it is crucial to develop an efficient data caching mechanism for UE while taking into account users’ mobility patterns. In this work, we propose a mobility-aware data caching approach to enhance data offloading via D2D communication. First, we model users’ connectivity patterns. Then, contents are cached in UE’ cache resources based on users’ data preferences. In addition, we also take into account signal-to-interference and noise ratio (SINR) requirements of the users. Hence, our proposed caching mechanism exploits connectivity patterns of users to perform data placement based on users’ own demands and neighboring users to enhance data offloading via cache resources. We performed extensive simulations to investigate the performance of our proposed mobility-aware data caching mechanism. The performance of our proposed caching mechanism is compared to most deployed data caching mechanisms, while taking into account the dynamic nature of the wireless channel and the interference experienced by the users. From the obtained results, it is evident that our proposed approach achieves 14%, 16%, and 11% higher data offloading gain than the least frequently used, the Zipf-based probabilistic, and the random caching schemes in case of an increasing number of users, cache capacity, and number of contents, respectively. Moreover, we also analyzed cache hit rates, and our proposed scheme achieves 8% and 5% higher cache hit rate than the least frequently used, the Zipf-based probabilistic, and the random caching schemes in case of an increasing number of contents and cache capacity, respectively. Hence, our proposed caching mechanism brings significant improvement in data sharing via D2D communications.

Because of their simple design structure, end-to-end deep learning (E2E-DL) models have gained a lot of attention for speech enhancement. A number of DL models have achieved excellent results in eliminating the background noise and enhancing the quality as well as the intelligibility of noisy speech. Designing resource-efficient and compact models during real-time processing is still a key challenge. In order to enhance the accomplishment of E2E models, the sequential and local characteristics of speech signal should be efficiently taken into consideration while modeling. In this paper, we present resource-efficient and compact neural models for end-to-end noise-robust waveform-based speech enhancement. Combining the Convolutional Encode-Decoder (CED) and Recurrent Neural Networks (RNNs) in the Convolutional Recurrent Network (CRN) framework, we have aimed at different speech enhancement systems. Different noise types and speakers are used to train and test the proposed models. With LibriSpeech and the DEMAND dataset, the experiments show that the proposed models lead to improved quality and intelligibility with fewer trainable parameters, notably reduced model complexity, and inference time than existing recurrent and convolutional models. The quality and intelligibility are improved by 31.61% and 17.18% over the noisy speech. We further performed cross corpus analysis to demonstrate the generalization of the proposed E2E SE models across different speech datasets.

The present chapter aims to describe the strategies involved in synthesis and functionalization of chitosan-built nano-hydrogel as smart drug carrier for various cationic, anionic, hydrophilic, and hydrophobic drugs at the physiological condition. An overview of nano-hydrogel processing, the desired surface-modification or induced sensitivity (induced hydrophilicity, hydrophobicity, glucose-sensing, and self-assembling) with respect to selective anionic/cationic drug loading and release mechanisms is highly stressed to discover the art of in-situ gelling system. The art of various chitosan-built nano-hydrogel and their structure–property-relationship is explained to support and establish the fact that, chitosan is the most promising biomaterial to be applied for various pharmaceutical and biomedical applications, particularly as a smart drug carrier for a variety of cationic and anionic (hydrophilic/hydrophobic) drugs.

Self-organized and vertically oriented TiO2 nanotubes (TNTs) were synthesized via anodization of Ti sheet in a glycerol-based used electrolyte. Graphite (Gt) is doped in TNTs by physical vapor deposition (PVD) under Ar-atmosphere at 700 °C using polyvinyl alcohol (PVA) as a precursor. The samples were characterized using FESEM, HRTEM, XRD, Raman, XPS, and UV–vis diffuse reflectance spectroscopy. HRTEM, XRD, and Raman analysis confirm the suppression of phase transformation from anatase to rutile due to Gt doping. The UV–vis absorption properties and photocatalytic activity of the pristine and Gt-doped TNTs have been investigated. The bandgap absorption edge of Gt-doped TNTs shifts towards a higher wavelength (~ 550 nm) compared to the pristine TNTs (~ 390 nm). Moreover, the Gt-doped TNTs show strong absorption in the visible region. This makes it a good candidate for energy-storing applications. It has been found that Gt-doped TNTs display two-fold enhanced photocatalytic activity for methyl orange (MO) degradation compared to pristine. The enhanced photo-degradation of Gt-doped TNTs is ascribed to the higher absorptivity, better crystallinity, and lower bandgap of TNTs due to Gt doping. The enhanced photo-degradation ability of Gt-doped TNTs can be used to clean industrial wastewater.

The non-existing properties of the metamaterial surfaces can be utilized to improve the antenna radiation characteristics. In this article, a design and performance analysis of a Single Negative (SNG) metamaterial based antenna is imparted for LTE 46/WLAN and Ka-band (like in satellite communication for the receiving side) applications. The unit cell of the metamaterial surface exhibits negative permittivity and positive permeability; yielding a high magnitude positive refractive index, is used to improve and analyze the performance of the proposed monopole antenna element. The proposed SNG based antenna covers a −10 dB bandwidth from 5.35-5.69 GHz (LTE 46/WLAN) and 17.81-20.67 GHz (Ka-band). The total size of the proposed antenna element is $20.2\times 28$ .4 mm2 while a $2\times 3$ SNG metamaterial surface is used at the back of the antenna element which improves the gain from 4.52 dB to 9.13 dB for the desired Ka band and 1.17 to 5.04 dB for the LTE 46/WLAN band. Furthermore, for the LTE 46/WLAN frequency band, the impedance matching also gets better, resulting in the return loss improvement from −11 dB to −32.4 dB. Moreover, the radiation efficiency is also improved by more than 10 % for the Ka band after employing the SNG metamaterial surface. The measured results fall in good agreement with the simulated one and make the proposed SNG metamaterial based antenna design competent for the LTE 46/WLAN and Ka-band (like in satellite communication for the receiving side) applications.

This paper presents a multiple-input multiple-output (MIMO) antenna system for millimeter-wave 5G wireless communication services. The proposed MIMO configuration is composed of four antenna elements, where each antenna possesses an HP-shaped configuration that features simple configuration and excellent performance. The proposed MIMO design can operate at a very wideband of 36.83–40.0 GHz (measured). Furthermore, the proposed MIMO antenna attains a peak gain of 6.5 dB with a maximum element-isolation of −45 dB. Apart from this, the MIMO performance metrics such as envelope correlation coefficient (ECC), diversity gain, and channel capacity (CCL) are analyzed, which demonstrate good characteristics across the operating band. The proposed antenna radiates efficiently with a radiation efficiency of above 80% at the desired frequency band which makes it a potential contender for the upcoming communication applications. The proposed design simulations were performed in the computer simulation technology (CST) software, and measured results reveal good agreement with the simulated one.

This paper presents a metasurface based multiple-input multiple-output (MIMO) antenna with a wideband operation for millimeter-wave 5G communication systems. The antenna system consists of four elements placed with a 90 degree shift in order to achieve a compact MIMO system while a $2\times 2$ non-uniform metasurface (total four elements) is placed at the back of the MIMO configuration to improve the radiation characteristics of it. The overall size of the MIMO antenna is $24\times 24$ mm 2 while the operational bandwidth of the proposed antenna system ranges from 23.5-29.4 GHz. The peak gain achieved by the proposed MIMO antenna is almost 7dB which is further improved up to 10.44 dB by employing a $2\times 2$ metasurface. The total efficiency is also observed more than 80% across the operating band. Apart from this, the MIMO performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL) are analyzed which demonstrate good characteristics. All the simulations of the proposed design are carried out in computer simulation technology (CST) software, and measured results reveal good agreement with the simulated one which make it a potential contender for the upcoming 5G communication systems.

The limited shelf life of carbon prepreg waste (CPW) from component manufacturing restricts its use as a composite reinforcement fibre on its own. However, CPW can be recycled with glass fibre (GF) reinforcement to develop a unique remediate material. Therefore, this study fabricated (1) a glass fibre-carbon prepreg waste reinforced polymer hybrid composite (GF-CPW-PP), (2) a polypropylene composite (PP), (3) a carbon prepreg waste reinforced composite (CPW-PP), and (4) a glass fibre reinforced composite (GF-PP) and reported their degradation and residual tension properties after immersion in water. The polymer hybrid composites were fabricated via extrusion technique with minimum reinforce glass-carbon prepreg waste content of 10 wt%. The immersion test was conducted at room temperature using distilled water. Moisture content and diffusion coefficient (DC) were determined based on water adsorption values recorded at 24-h intervals over a one-week period. The results indicated that GF-PP reinforced composites retained the most moisture post-168 h of immersion. However, hardness and tensile strength were found to decrease with increased water adsorption. Tensile strength was found to be compromised since pores produced during hydrolysis reduced interfacial bonding between glass fibre and prepreg carbon reinforcements and the PP matrix.

Here, the structure-dependent electronic, thermal, and transport properties of nanostructured thallium telluride (Tl 8 Pb x Sb 2− x Te 6 ) through controlled variation in Pb and Sb (x = 1.96, 1.97, 1.98, 1.99) concentrations have been investigated. In the temperature and concentration-dependent electrical conductivity measurements, the highest electrical conductivity 131.96 × 10 3 Ω − 1 m − 1 at 300 K was measured for x = 1.99 and the maximum observed Seebeck value for the optimized Tl 8 Pb 1.96 Sb 0.04 Te 6 nanoparticles was 110.7 μ V/K at 550 K. Such an increased value of the Seebeck coefficient led to the achievement of a significantly improved high-power factor, which was found to be increasing with temperature and decreasing with the increase of Pb concentration. The density functional theory calculations performed for Pb and Sb co-doped Tl 5 Te 3 resulted in the enhanced σ e and S with a significant reduction in electronic thermal conductivity ( κ e ) and is found consistent with experimentally measured κ e . The highest ZT = 0.35 and 0.18 were recorded experimentally and theoretically for Pb and Sb co-doped in Tl 5 Te 3 nanoparticles.

Abstract Protic ionic liquids (PILs) being intrinsic proton conducting ionic species are considered as potential green electrolytes for study of electrocatalytic reactions and for fabrication of IL-based fuel cells (FCs) and batteries. We have prepared a sulfate anion based protic ionic liquid (PIL), triethylammonium sulfate (TEAS) through a reaction involving transfer of proton from H2SO4 to triethylamine (TEA). 1H NMR and FT-IR spectroscopic techniques were employed for confirmation of the synthesis of TEAS and water content of the PIL was quantified using coulometric Karl–Fischer (KF) titration. 1H NMR and FT-IR analysis confirm the synthesis of the PILs and KF-titration analysis shows that TEAS contains 1.43 w/w % water. Electrical conductivity of TEAS was determined at different temperatures showing that the PIL has excellent ionic conductivity that enhances with rise in temperature of the medium. The temperature dependence of the conductivity of the PIL follows the Arrhenius equation as the logσ versus 1/T plot is linear. The electrochemical windows (EWs) of the electrolyte were found using cyclic voltammetry at Pt and Au working electrodes and found to decrease with increase in temperature of the medium. The data revealed that the surfaces of the electrodes are covered with oxide layers due to oxidation of trace water (1.43 w/w %) present in the PIL. The oxide layers growth increase and their onset potential moves to less positive values as the temperature of the PILs is increased. The data was compared with the literature and would be helpful in understanding of the surface electrochemistry in this neoteric medium for being used as potential electrolyte in industry for various electrochemical applications.

Ionic liquids (IL) are known to act as plasticizer. This work is first report to best of our knowledge, of an amphiphilic ionic liquids (IL), 1-hexadecyl-3-methylimidazolium bromide [C16mim][Br] acting not only as a plasticizer but also as a nucleating agent during crystallization of poly (vinylidene fluoride). With FTIR-ATR, XRD, DSC, and SEM, It is observed that plasticizing and nucleating role of mentioned IL is due to its self-assembling property in fluoropolymer matrix. At 1% loading of [C16mim][Br] in PVDF matrix, it speeds up the crystallization of PVDF accompanied by formation of finger like structure, while at (10%) loading, the formation of micellar structure promote plasticization and PVDF crystallizes at low temperature. Fortunately, in both cases polarized (β/γ) crystal formation is favored.