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AbstractTensile stresses may lead to cracks forming at the crest of coastal slopes and subsequent slope failure, particularly under seismic load conditions. Traditional shear strength failure criteria often overestimate the tensile strength of geomaterials, and in turn the factor of safety against sliding. This paper presents an improved nonlinear analysis method for assessing the stability of slopes, while considering tension cut-off in the failure criterion as well as the detrimental effects of inertial seismic loading and pore water pressure. The method employs the principle of energy consumption to obtain solutions for the geometry of the potential sliding surface and stress distribution, while the critical slope height and the stability factor are determined by means of a particle swarm optimization algorithm. Comparison with existing methods is conducted to validate the effectiveness and accuracy of this method. Results showed that the tensile strength of geomaterials had a significant impact on the stability of the slope and its associated failure mechanism, particularly for the vertical slope. This study could avoid the assumptions of the dilatancy angle on the velocity discontinuity and critical slope sliding surface, and reflect the tensile and nonlinear characteristics of the geomaterials well. [ABSTRACT FROM AUTHOR]

The sonochemical synthesis, structural analysis, theoretical calculations, and the nonlinear optical (NLO) discovery of benzylidenehydrazono thiazolidin-4-one derivative 8, that is, (Z)-ethyl-2-((Z)-2-((E)-(4-chlorobenzylidene)hydrazono)-4-oxo-3-phenylthiazolidin-5-ylidene) acetate (C20H16ClN3O3S), are detailed. The 1H and 13C NMR data, melting point (m.p), infrared spectrum (IR), mass spectrum, and UV–visible spectrum measurements are used to confirm the authenticity of the synthesized derivative 8. The geometrical structural optimizations and theoretical properties of the synthesized compound are performed using density functional theory (DFT). The NLO properties of the synthesized derivative 8 are studied under continuous wave (cw) 473-nm laser beam via conducting the closed (C)- and open (O)-aperture (A) Z-scan techniques where the nonlinear refractive index (NLRI) and the nonlinear absorption coefficient (NLAC) are obtained, viz. 1.79 × 10−7 cm2/W and 2.72 × 10−3 cm/W, respectively, and an optical limiting (OLg) threshold of 13 mW is obtained. [ABSTRACT FROM AUTHOR]

Due to their excellent nonlinear optical characteristics, tellurium-zinc glass and perovskite structures have gained significant attention. In particular, perovskite-type BaTiO 3 shows excellent potential for application in photonics devices. This study investigates structural, linear, and nonlinear optical properties of pure tellurium-zinc glass with embedded perovskites. Both glasses were prepared using the conventional melt-quenching method, and their structural modifications were analyzed through Raman spectroscopy. Optical absorption spectra revealed a redshift in the absorption edge, indicating a decrease in the band gap energy by the presence of the perovskite nanoparticles. When adding perovskite nanoparticles, Raman scattering results demonstrated decreased bridging and non-bridging oxygen ratio and structural changes. This suggests that the perovskite nanoparticles alter the local environment by affecting the Te-O- Zn2+ or Te=O bonds, resulting in a variation of the polarizability. Finally, the average nonlinear refractive for the glass containing perovskite nanoparticles is on the order of 0.3 × 10−18 m2 W−1 in the wavelength range of 580–990 nm, which is the same as of the pure glass. Thus, while the NP particles influence the arrangement of structural units and the linear optical response, their impact is not significant in the nonlinear refractive index. The observed modifications in structural and optical properties are relevant for advancing the use of perovskites in photonics. • Pure tellurium-zinc glass and perovskite BaTiO 3 tri-doped Er/Yb/Zn embedded in tellurium-zinc glass were prepared through the melt-quenching method. • Raman spectroscopy reveals changes in bridging and non-bridging oxygen ratios. • The band gap (E g) decreases in the presence of BaTiO 3 tri-doped Er/Yb/Zn from 3.5 to 3.2 eV. • The nonlinear refraction index was assessed by the femtosecond Z–scan technique. [ABSTRACT FROM AUTHOR]

Thin films of strontium titanate, which have nonlinear properties that are promising for microwave applications, were grown on a polycrystalline aluminum oxide substrate using magnetron sputtering and high-temperature annealing. It was shown that the improvement of the film structure with an increase in the deposition temperature was clearly correlated with both an increase in nonlinearity and an improvement in the loss level. A capacitor based on an SrTiO3 film deposited at a deposition temperature of 900 °C and subjected to annealing demonstrated a tunability of 46% with a loss tangent of 0.009–0.014 at a frequency of 2 GHz. This was the first successful attempt to form a planar SrTiO3 capacitor on an alumina substrate, which exhibited a commutation quality factor of above 3000 in the microwave range. [ABSTRACT FROM AUTHOR]

Nonlinear optical properties of metallic and oxide metallic nanoparticles have been extensively studied as saturable absorbers in fiber-optic lasers in the infrared region for the generation of short and/or ultrashort pulses. In this paper, we report an experimental study of the nonlinear optical response of silver and zinc nanoparticles for continuous-wave illumination at 1550 nm. Nonlinear absorption was investigated using the power-dependent transmission and Z-scan techniques. The results obtained from the first technique showed that the zinc and silver particles behave like saturable absorbers, the modulation depths obtained were 15 % and 32 %, respectively. The Z-scan technique showed the presence of nonlinear refraction and absorption in both samples, the open aperture configuration confirmed the behavior of the materials as saturable absorbers. Additionally, the nonlocality of the nonlinear response was analyzed using a numerical model.

The present study reports the annealing induced structural as well as optical properties of Ag 2 S/As 2 Se 3 heterostructure film at different annealing temperatures. The trigonal AgAsSe 2 phase formation was confirmed from the X-ray diffraction (XRD) and selective area electron diffraction (SAED) study. The bandgap of as-prepared Ag 2 S/As 2 Se 3 film decreased on annealing. The reduction in bandgap increased the static refractive index with annealing. The Urbach energy increased from 422±3 meV to 464±2 meV whereas the optical density and extinction coefficient increased by annealing due to the formation of AgS–AsSe solid solution. The dispersion energy increased and consequently increased the oscillator wavelength and oscillator strength upon annealing. The carrier concentration and optical conductivity increased whereas the optical electronegativity decreased with annealing. The 3rd order nonlinear susceptibility (χ(3)) increased from 2.804x10−11 esu (as-prepared Ag 2 S/As 2 Se 3) to 5.132 x10−11 esu upon annealing at 200 °C. The n 2 value increased upon annealing which increased the nonlinear absorption coefficient but decreased the figure-of-merit. The contact angle value decreased (93°–47.6°) that shows the transformation of hydrophobicity to hydrophilic nature which is good for sensor applications like biological sensor. The surface roughness decreased upon annealing. The change in optical parameters upon annealing makes them the appropriate candidate for optoelectronics, dielectric and nonlinear optical applications such as memory devices, optical switch, etc. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, PEO/NiO films composed of polyethylene oxide (PEO) and nickel oxide (NiO) were fabricated using solution cast method to be used in optoelectronics applications. The PEO/NiO films are irradiated by oxygen fluence of 0.8 × 1018, 1.6 × 1018, and 2.4 × 1018 ions/cm2. The XRD as well as FTIR techniques were used to assess the effect of ion bombardment on the crystalline structures and functional group of PEO/NiO films. The absorption (A) and reflection (R) of the untreated and irradiated films was determined using UV–vis spectrophotometer in wavelength range of 200 to 1000 nm at room temperature. The data of A and R were used to calculate the parameters including band gap (Eg), absorption coefficient (α) and refractive index (n). The band gap as well as Urbach energies of un-bombarded as well as bombarded PEO/NiO films was calculated by Tauc's relationship. The band gap is reduced from 3.37 eV for PEO/NiO, to 2.66 eV, 2.57 eV and 2.50 eV after exposed to 0.8 × 1018, 1.6 × 1018, and 2.4 × 1018 ions/cm2 correspondingly, Moreover, the ubrach band tail is increased from 1.25 eV for PEO/NiO to 1.36 eV,1.41 eV and 1.45 eV after oxygen irradiation respectively. Additionally, linear optical characteristics have been calculated, including the refractive index and dielectric constant. The dispersing factors of the investigated films have also been computed using the Wemple-Di-Domenico model. The non-linear optic susceptibilities and refractive indices are calculated for un-bombarded as well as bombarded films. This work concluded that the optical behaviour of the bombarded PEO/NiO composite films were modified, indicating that these composites films can used in optoelectronics devices. [ABSTRACT FROM AUTHOR]

The rising industrial demand for technological advancement in improving their working fluids and thermal augmentation has prompted studies on various non-Newtonian fluids and nanofluids. These play momentous role in many engineering devices and electronics development. Therefore, this study seeks to examine the thermal performance of ternary hybridized magneto-couple stress nanofluids in permeable media with nonlinear thermofluidic properties. The dispersion of suspended cobalt ferrite CoFe2O4, titanium dioxide TiO2 and magnesium oxide MgO nanoparticles occurs in H2O conventional solvent. With isothermal energy, the tri-hybrid nanofluid is controlled by stretchy velocity, magnetic field, gravity and Ohmic heating. An invariant transmutation of the partial derivative model is offered using similarity variables. The complete solutions to the model are obtained via Chebyshev technique coupled with integrated collocation method. From the graphically presented results, it is revealed that strong heat transfer is provided by ternary CoFe2O4+Ti02+MgO nanofluids compared to CoFe2O4+Ti02 and CoFe2O4 nanofluids. Also, the nanofluid concentration volume fraction enhanced thermal distribution and performance in the system.

Plasmonic nanocomposites have been extensively studied for over 3 decades. According to early theoretical studies, a large enhancement of nonlinear response has been predicted. Nonetheless, the promised enhancement of coherent or Kerr‐type nonlinearities incurs major limitations related to strong absorption and saturation effects. Accordingly, diffraction‐limited interactions and long‐scale propagation in ultrafast timescales are undermined despite nanoscale‐localized electronic field enhancement. Seemingly only nanometric devices operating at low intensity regimes are benefitted from the foresaid effect. Nonetheless, numerous studies have still exploited configurable properties of the nonlinear response of plasmonic nanocomposites, such as nonlinear absorption, high‐order nonlinearities, and diffusive nonlinearities for the development of novel processes within the framework of nonlinear wave propagation described by effective medium properties. In this review, the most recent developments on the understanding of the nonlinear response of metals and plasmonic nanocomposites in various temporal regimes are presented. Furthermore, a synthesis of their experimentally determined third‐order properties obtained by various experimental techniques, along with practical considerations, is provided. Computational models used for the formulation of nonlinear wave propagation in plasmonic nanocomposites are subsequently presented, corresponding to applicable concepts. Most recent related applications are concisely summarized, indicating the directions of increasing interest in the field, and outlining shortcomings. [ABSTRACT FROM AUTHOR]

The interaction of an electromagnetic beam with a sharp boundary of a dense cold semi-limited plasma was considered in the case of a normal wave incidence on the plasma surface. The possibility of the appearance of an electrostatic field outside the plasma was revealed, the intensity of which decreased according to the power law with a distance from the plasma and the center of the beam. It was possible to form cavities with a reduced electron density, being each electromagnetic resonators, which probed deeply into the dense plasma and couldexist in a stable state for a long period. [ABSTRACT FROM AUTHOR]

The tellurium (Te)‐doped Ag60‐xSe40Tex (x = 0%, 5%, 10%, 15%) thin films of thickness ∼800 nm were prepared from the bulk sample by thermal evaporation method on a glass substrate. The X‐ray diffraction study revealed the amorphous nature of the films whereas the change in vibrational modes was noticed from the Raman spectroscopy. The composition of the films was verified by energy dispersive X‐ray analysis and the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in optical properties (linear and non‐linear) with Te addition were studied from UV‐Visible spectroscopy data and related empirical formulas. The addition of Te reduced the bandgap values significantly and the reduction in transmission resulted in the increase of the linear refractive index. The decrease in optical bandgap is due to an increase in disorder while the width of the tail in the gap increased with Te%. The optical density, dispersion energy, extinction coefficient, carrier concentration, dielectric constant, oscillator wavelength increased while the oscillator energy, oscillator strength, optical electronegativity decreased with Te content. The electrical susceptibility increased with Te content. The non‐linear susceptibilities and the non‐linear refractive index increased which is good for the nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

The Ca site of CaCu3Ti4O12 (CCTO) ceramics doped by strontium (Ca1-xSrxCu3Ti4O12, x = 0.0, 0.1, 0.2, 0.3) were accomplished by a modified sol–gel method and subsequently sintered at 980–1020 °C to improve the dielectric properties and enhance the breakdown electric field. Remarkably, the dielectric loss (tanδ) of the CSCTO ceramics sintered at 1000 °C can be lower than 0.05 in a wide frequency (20 Hz–100 kHz), especially, very low dielectric loss (tanδ) about 0.008 can be obtained in Ca0.9Sr0.1Cu3Ti4O12 ceramic which sintered at 1000 °C measured at 300 Hz. These results indicate that Sr2+ doped at the Ca2+ site of CCTO type ceramic can enhance the applicable properties of CaCu3Ti4O12 and can be used in the future practical researches. [ABSTRACT FROM AUTHOR]

The present paper illustrates the influence of the top Ag and Te thin layer on the linear and nonlinear optical properties of Ag(Te)/As50Se50 bilayer thin films. The As50Se50 and Ag(Te)/As50Se50 bilayer thin films were prepared by thermal evaporation technique under high vacuum conditions. The X-ray diffraction study showed no structural changes, whereas the UV–Visible spectroscopy data showed the changes in optical properties due to top layer deposition. From the recorded optical transmission data, the optical parameters, such as absorption coefficient, extinction coefficient, optical bandgap, Tauc parameter, Urbach energy, linear refractive Index, oscillator energy, dispersion energy, high-frequency dielectric constant and carrier concentration, were evaluated. The transmittance decreased and the absorption coefficient increased along with the increase in extinction coefficient. The optical bandgap decreased due to the increase in defect states and the degree of disorder. The dispersion of the refractive index was analyzed by the single oscillator Wemple–Di Domenico model. The third-order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n2) were calculated from the linear optical parameters using semi-empirical relations. The linear, nonlinear refractive index and (χ(3) change was found to be more in Te/As50Se50 film than that of Ag/As50Se50 film as compared with the host As50Se50 film. The surface morphology was investigated by field emission scanning electron microscopy. The tuning of optical properties by simple layer deposition on the host matrix can be used in various optoelectronic applications. [ABSTRACT FROM AUTHOR]

Problems concerning structures dynamics are being one of most important subjects in recent investigations associated with railways constructions. The need of modelling of such structures and their behaviour prediction leads to necessity of seeking new approaches, mainly due to highly increasing speeds of vehicles and traffic intensity. Comparative studies carried out on experimental data, measurements and theoretical research show that models based on multi-layered approach supported by semi-analytical approximations of solutions can give new insight into undertaken analyses. More detailed consideration of roads components and their physical properties, along with application of effective estimations allowing to avoid numerical instabilities linked with extremal dynamic variations, can be important tools in obtaining new solutions both, theoretical and engineering. This paper briefly presents a number of multilayer railway track models, with special emphasis on nonlinear track properties. Existing analytical and semi-analytical solution methods are presented with main advantages of new approaches. The theoretical double-beam system with two nonlinear layers is solved and computational examples are presented along with possibility of their transition to other multilayer structures analysis.

The properties of crystalline materials can be described mathematically by tensors whose components are generally known as property constants. Tabulations of these constants in terms of the independent components are well known for common material properties (e.g. elasticity, piezoelectricity etc.) aptly described by tensors of lower rank (e.g. ranks 2–4). General relationships between constants of higher rank are often unknown and sometimes reported incorrectly. A computer program is developed here to calculate the property constant relationships of a property of any order, represented by a tensor of any rank and point group. Tensors up to rank 12, e.g. the tensor of sixth‐order elastic constants , can be calculated on a standard computer, while ranks higher than 12 are best handled on a supercomputer. Output is provided in either full index form or a reduced index form, e.g. the Voigt index notation common to elasticity. As higher‐order tensors are often associated with nonlinear material responses, the program provides an accessible means to investigate the important constants involved in nonlinear material modeling. The routine has been used to discover several incorrect relationships reported in the literature. [ABSTRACT FROM AUTHOR]

• Synergistic effects of Er 2 O 3 doping and two stage sintering of ZnO varistors were studied. • Fully dense and fine grained ZnO varistors were prepared. • Varistors exhibited high breakdown voltage and nonlinear exponent. • Nonlinear electrical property was correlated with various barrier parameters. High performance Er 2 O 3 doped ZnO-V 2 O 5 based varistors were prepared by two stage sintering (TSS) method at T 1 = 1050 °C for 1/6 h and T 2 = 750 and 800 °C for 2.5, 10, 20 and 40 h duration. The microstructural features and electrical properties were studied by XRD, SEM, EDS and a high voltage source unit. The combined effect of TSS and Er 2 O 3 doping is very beneficial to restrain the grain coarsening of varistors. The effect of grain size reduction on nonlinear electrical properties was investigated. The results showed that superior electrical properties were obtained in doped samples via TSS than single stage one. A typical fine-grained (1.7 μm, 97.5 %TD) varistor with sufficiently high nonlinear exponent (α = 154), breakdown field (E B = 15.2 kV cm−1) and reasonably low leakage current density (J L = 0.13 mA cm-2) could be prepared with 0.5 mol.% Er 2 O 3 doping at an optimum sintering condition of T 1 /T 2 = 1050/750 °C for 40 h. [ABSTRACT FROM AUTHOR]

SrCO3 was used as a nonlinear-forming additive for ZnO-based ceramics. The Sr-doped ZnO ceramics were synthesized by the conventional solid-state method and their performance was studied systematically. The Sr-doped samples showed nonlinear current-voltage properties with a max nonlinear coefficient of 6.26. The structural and morphological characterizations pinpointed the formation of the intergranular phase, which was related to the segregation of Sr at the grain boundary. The electrical modulus spectra and impedance spectra were interpreted by the relaxation behaviours correlated with the grain boundary effect and oxygen vacancies. Meanwhile, the increase of the grain boundary resistance was also ascribed to the influence of Sr doping. These detailed studies demonstrated the potential of Sr-doped ZnO ceramics and provided a guidance to prepare a bismuth-free ZnO-based varistor. [ABSTRACT FROM AUTHOR]

This study expands on a previous investigation by substituting lanthanum with various trivalent ions in the compound (Ca 0.9 Sr 0.1) 0.95 A 0.033 Cu 3 Ti 4 O 12 (A = La3+, Sm3+, Sc3+, Gd3+, Y3+ and Bi3+) through solid-state synthesis. The analysis includes microstructures, optical, dielectric, and nonlinear properties. Sr2+/A3+-doped CCTO exhibits a significant reduction in grain size. The doped samples display a band gap ranging from 3.22 eV to 3.36 eV, with high dielectric permittivity (ε '≈4.51 × 103-5.37 × 104). Additionally, Sr2+/A3+ doping enhances the thermal stability compared to pure CCTO ceramic. Specifically, Sr2+/Sc3+-doped compound shows low loss tangent (tanδ≈0.04) at 60 °C, with the dielectric loss remaining below 0.1 over a temperature range from 50 °C to 160 °C. Furthermore, there is a significant improvement in breakdown voltage (E b = 8420 V/cm), which is 23 times higher than CCTO (362.5 V/cm), and the coefficient α increases from 3.28 to 12.76. These enhancements are attributed to inhibiting the formation of Ti3+ and reducing oxygen vacancies. [Display omitted] • (Ca 0.9 Sr 0.1) 0.095 A 0.033 Cu 3 Ti 4 O 12 (CSACTO) ceramics were successfully prepared by a conventional solid-state reaction method. • High permittivity (έ ≈ 4.51 × 103- 5.37 × 104). • Low dielectric loss tanδ ≈ 0.04 at 60 °C and 1 kHz. • The E b of CaCu 3 Ti 4 O 12 is improved from 362.5 to 8420 V/cm by Sr/Sc doping. [ABSTRACT FROM AUTHOR]

• Impact of heat treatment on NLO features of Nd 2 O 3 doped borate glasses embedded with Ag NPs has been investigated. • NLO features were studied in near infra-red region under ultrafast regime. • The origin of enhancement of NLO features has been highlighted. • The nonlinear results reveal the investigated glasses are beneficial for optical limiting devices. Nd3+ ions containing borate glasses embedded with silver (Ag) nanoparticles (NPs) were prepared by melting and quenching process. Thermal treatment at 450 °C for different holding durations has been performed to tune the size of the NPs embedded in the glass. The influence of growth of NPs on nonlinear optical (NLO) and optical limiting (OL) properties of glasses has been evaluated in the near–infrared spectral provenience under femtosecond pulse regime. The NLO and OL attributes evaluated using Z–scan configuration disclose the enhanced trend of two–photon absorption and nonlinear refraction coefficients and a decrease behaviour of OL threshold with the augment of thermal holding time. This enhancement in NLO coefficients and OL performance with thermal annealing duration is ascribed to the enhancement of the local field with the size of the NPs. The outcomes acknowledge the Nd3+ ions bearing borate glasses embedded with bigger Ag NPs are preferable for nanophotonic applications and optoelectronic functionalities. [ABSTRACT FROM AUTHOR]

Graphene is a unique 2D material that has been extensively investigated due to its extraordinary photonic, electronic, thermal, and mechanical properties. Excited plasmons along its surface and other unique features are expected to play an important role in many emerging photonic technologies with drastically improved and tunable functionalities. This review is focused on presenting several recently introduced photonic phenomena based on graphene, beyond its usual linear response, such as nonlinear, active, topological, and nonreciprocal effects. The physical mechanisms and various envisioned photonic applications corresponding to these novel intriguing functionalities are also reported. The presented graphene‐based technologies promise to revolutionize the field of photonics at the relatively unexplored terahertz (THz) frequency range. They are envisioned to lead to the design of compact harmonic generators, low‐power wave mixers, linear and nonlinear sensors, magnet‐free isolators and circulators, photonic topological insulators, modulators, compact coherent optical radiation sources, and subwavelength imaging devices.

A conventional ceramic processing method was applied to manufacture high‐density 20‐nm ZnO‐Bi2O3‐Mn2O3 varistor ceramics. Different cooling rates in the range of 135–540°C/h led to a relatively slight influence on the microstructure, varistor voltage, and leakage current. In contrast, these rates strongly affected the nonlinear exponent. The specific surface area of the 20‐nm ZnO nanoparticle may have led to an intense solid‐state reaction even at a low cooling rate. Superior nonlinearity, with 59.7 μA nonlinear current leakage and 273.5 μA leakage current, was achieved at the 135°C/h cooling rate. The differences in the cooling rates led to a remarkable change in the material's stability under direct current (DC)‐accelerated aging stress in the following order: 135°C/hr ˃ 270°C/hr˃405°C/hr ˃ 540°C/hr. [ABSTRACT FROM AUTHOR]

The interaction of an electromagnetic beam with a sharp boundary of a dense cold semi-limited plasma was considered in the case of a normal wave incidence on the plasma surface. The possibility of the appearance of an electrostatic field outside the plasma was revealed, the intensity of which decreased according to the power law with a distance from the plasma and the center of the beam. It was possible to form cavities with a reduced electron density, being each electromagnetic resonators, which probed deeply into the dense plasma and couldexist in a stable state for a long period.

Herein, we have developed the thin Gd@PbI2 films on FTO via a facile spin coating route and subjected to various studies. The formation of (001) oriented hexagonal phase Gd:PbI2/FTO films was confirmed by X-ray diffraction & FT-Raman spectroscopy analyses. The size was determined through Scherrer formula in 11–16 nm range. The doping of Gd and its homogeneity was tested and approved by EDX and SEM e-mapping studies. The Gd doping impact on surface morphology was inspected via SEM images and found very low dimension grains formation throughout the films area. Tauc's formula was employed to obtain energy gap and found in 2.46–2.74 eV for all Gd@PbI2 films. Absorption and refractive indices were estimated in 0.034–1.2 and 1.4–11 between 395 and 2400 nm wavelength regions. Respective dielectric constant and loss values were noted between 3.5 and 112, and 0.13 and 1.4, signify high dielectric constant and low loss values. The optical conductivity was calculated of 1016 order for all Gd@PbI2 films. SELF and VELF related values were also determined. The values of nonlinear optics related parameters were also calculated and revealed that the grown films are potential candidates for opto-nonlinear devices. [ABSTRACT FROM AUTHOR]

The coefficients embodied in a Boussinesq-type model are very important since they are determined to optimize the linear and nonlinear properties. In most conventional Boussinesq-type models, these coefficients are assigned the specific values. As for the multi-layer Boussinesq-type models with the inclusion of the vertical velocity, however, the effect of the different values of these coefficients on linear and nonlinear performances has never been investigated yet. The present study focuses on a two-layer Boussinesq-type model with the highest spatial derivatives being 2 and theoretically and numerically examines the effect of the coefficient a on model performance. Theoretical analysis show that different values for α (0.13⩽α⩽0.25) do not have great effects on the high accuracy of the linear shoaling, linear phase celerity and even third-order nonlinearity for water depth range of 0

The photo and thermal annealing induced linear and nonlinear optical properties, structural properties and surface morphology of thermally evaporated Ag/GeS bilayer thin films are reported in the present study. The related changes due to Ag diffusion into GeS layer by annealing at 200 °C and 532 nm laser irradiation have been probed. The X-ray diffraction revealed no structural change whereas the surface structure was viewed by field emission scanning electron microscopy. The optical data recorded by UV–visible spectrophotometer in the range of 500–1200 nm shows the decrease in refractive index (n) and extinction coefficient (k). The Ag diffusion into GeS layer increased the optical band gap due to the decrease of width of the localised states. The single oscillator Wemple–Di Domenico model was used to study the dispersion relation. The third order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n2) were calculated by using suitable semi-empirical relation. The change in density of defects and localised states explained the observed linear and nonlinear changes with annealing and laser irradiation. The homopolar bond to heteropolar bond transformation is noticed from X-ray photoelectron spectroscopy. The observed optical changes can be used in various optical applications. [ABSTRACT FROM AUTHOR]

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The structural and electronic properties of InAs x Sb 1-x ternary alloys are studied using plane-wave pseudopotential method based on the density functional theory. The Born effective charge, elastic constants, phonon dispersion curves, linear and nonlinear optical properties of these compounds are calculated using density functional perturbation theory. Based on the calculated phonon frequency, the specific heat at constant volume and entropy are obtained within the harmonic approximation. Moreover, due to the density functional theory band gap problem, the band gap correction is performed within the one-shot GW approximations. The distinguished role of In 4d states on the electronic energy band gap and nonlinear properties of these alloys are extensively explored by the comparison between the calculated results of Hartwigsen-Goedecker-Hutter and Trouiller-Martins-type pseudopotentials. The calculated results show that InAs x Sb 1-x alloys are mechanically stable and can be a good candidate for high-performance nonlinear optical material. The calculated results of InAs and InSb compounds are in acceptable agreement with available theoretical and experimental results, so the calculated results of InAs x Sb 1-x alloys will be helpful for future experimental and theoretical investigations. Image 1 • The calculated elastic constants show that InAs x Sb 1-x ternary alloys are mechanically stable. • The one-shot GW approximation improves the energy band gap of these ternary alloys. • The Born effective charge and thermodynamic properties of these ternary alloys are studied. • The nonlinear response properties of InAs x Sb 1-x alloys are investigated. [ABSTRACT FROM AUTHOR]

The densification, microstructure and nonlinear electrical properties of ZnO-V2O5-MnO2-Nb2O5 varistor ceramics have been investigated with different amounts (0–2 mol.%) of Er2O3 addition. The ball milled powder mixtures have been sintered at 900°C, 1100°C and 1300°C for 1 h. The microstructure shows the presence of ZnO grains as the primary phase with secondary phases like Zn3(VO4)2, ErVO4, Zn4V2O9, Er- and Mn-rich in the intergranular layers. Generation of ErVO4 and Er-rich secondary phases at triple points and grain boundaries is found to inhibit grain growth resulting in the significant reduction of ZnO grain size, although this slightly diminishes the densification process. At a particular sintering temperature, the size of ZnO grains gets reduced over ten times when Er2O3 addition is increased from 0 mol.% to 2 mol.%. The nonlinear electrical property of the varistors improves with Er2O3 addition up to 0.5 mol.% and further addition (1–2 mol.%) does not appear to be beneficial in the chosen sintering temperatures. For varistors sintered at 1100°C, average ZnO grain size reduces from 10.8 μm in Er2O3 free sample to 7.2 μm in 0.5 mol.% Er2O3 added sample; this, in turn, significantly improves nonlinear electrical properties. The breakdown field increases from 1588 V cm−1 to 2585 V cm−1 with concurrent enhancement of nonlinear exponent value from 16 to 26 when Er2O3 concentration is raised from 0 mol.% to 0.5 mol.%. [ABSTRACT FROM AUTHOR]

Abstract NiO has been found to have excellent physical properties which are crucial for several significant electro-optical devices. Herein, we have designed and fabricated high-quality films of NiO with various concentrations of Ce and studied their key properties. X-ray diffraction (XRD) study confirmed the cubic phase, good crystallinity and growth direction along (111) plane in the prepared samples. The crystallite size was noticed in the range of 13–30 nm. For confirming the presence of Ce doping and its homogeneity in NiO films the EDX/SEM mapping was carried out. AFM study provided the topographic information in terms of size of the grains and roughness of all films. The grown films were found to be 70–80% optically transparent in the whole testing region. Optical energy gap was found to expand from 3.60 to 3.68 eV owing to Ce-doping. The refractive index value was noticed to be in the range from 1.7 to 2.7. The n 2 and χ (3) values for pure and Ce-doped NiO films varied from 2 × 10−10 to 1.4 × 10−11 and 1 × 10−12 to 1.1 × 10−11 esu, respectively. Obtained results indicated that Ce has strong influence on opto-nonlinear characteristics of NiO films and proposed their application in the opto-nonlinear devices. Highlights • Facile fabrication of Cu:NiO/glass films was achieved by spin coating technique. • UV–Vis–NIR study confirms high optical transparency of deposited films. • Energy gap was reduced from 3.87 to 3.8 eV due to Cu doping in NiO. • Third order nonlinear properties are enhanced due to N doping. • Values of n 2 and β are in range 8.36 × 10−9 to 1.18 × 10−9 cm2/W and 9.01 to 9.81 for all films. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Facile sol-gel spin coating technique is applied to fabricate N:ZnO/ITO thin films system. • Structural and vibrational studies confirm single phase with good crystalline nature. • EDX/SEM mapping confirm the N doping and its homogeneous distribution in ZnO films. • Fabricated films posses good optical transparency viz. ∼75–85%. • The χ 3 values are found in order of 10−8 for N:ZnO films compare to pure i.e. 10−11. Abstract Different concentrations of N (0, 1, 3 and 5 wt.%) added ZnO thin films were primed using spin coater. X-ray diffraction (XRD) patterns confirm the preferred growth orientation of all films along (0 0 2) plane, however, ITO has dominant features owing to low thickness of the films. XRD along with vibrational spectroscopy confirms the single hexagonal phase of ZnO. The crystallite size evaluated from Scherrer's equation increased with increase in N-doping concentrations and is found to lie in the range of 25–36 nm. The increased crystallite size reduces the dislocation density which confirms the reduction of defects in the films. The dislocation density (δ) is found to be 1.569, 1.369, 0.984, and 0.965 for 0, 1, 3 and 5 wt.% N doped ZnO films. N doping in ZnO was confirmed by EDX analysis and its homogeneous distribution was further confirmed by SEM mapping. AFM study confirms the formation of spherical nanoparticles whose size increase with increase in N doping, validating the XRD results. The films are found to have ∼80% transparency which is quite impressive from window layer application point of view. Absorption edge is found to be red shifted owing to N doping, indicating a reduction in energy gap. Hence energy gap was evaluated using Tauc's relation and is found to reduce from 3.43 to 3.14 eV (ΔE = 0.29 eV) with in content of N-doping. The absorption index, refractive index, real and imaginary dielectric constants were also estimated. The values of χ(1) and χ 3 are estimated to be in range of 0.3–9 and 1.0 × 10−11 - 1.0 × 10−8, respectively. The Nanocrystalline films with spherical nanocrystallites, high optical transparency and non-linear properties recommend their application in opto-electronic technology. [ABSTRACT FROM AUTHOR]

TiO2-based varistor-capacitor ceramics co-doped with fixed Nb2O5, MnO2, Sm2O3 and various content of Sb2O3 are prepared, and then the effect of Sb2O3 on electrical properties of TiO2 varistor-capacitor ceramics is investigated. The results indicate that addition of Sb2O3 effectively decreases breakdown voltage (E1mA), while having less impact on the nonlinear coefficient (α). E1mA initially increases and then decreases with Sb2O3 increasing; contrarily, relative dielectric constant (εr) decreases first and then increases. It is found that composition of 98.3%TiO2-0.8%Nb2O5-0.3%MnO2-0.3%Sm2O3-0.3%Sb2O3 is obtained with a low breakdown voltage of 2.3 V/mm, nonlinear coefficient of 2.0, high relative dielectric constant of 7.6 × 104 and low dissipation factor of 0.25, which is consistent with the narrowest grain boundary barriers in the composition. The nonlinear coefficient initially increases and then decreases with increase of Sb2O3; it reaches a maximum value of 2.9 at 0.2 mol.% Sb2O3, which is consistent with the highest grain boundary barriers in the composition. In order to explain the nonlinear current-voltage characteristics, a grain boundary defect barrier model was introduced. [ABSTRACT FROM AUTHOR]

Dense barium titanate (BaTiO3) ceramics ($d_{\text {rel}} > 95{\%}$) with a microscale grain size are obtained at 800 °C–1100 °C by a solid-state ceramic process. BaTiO3 (BT) doped with Co2+/3+ leads to a significant improvement in the properties ($d_{33}> 250$ pC/N). Soft and hard characteristics of the piezoceramics are observed depending on the dopant ions. The Co/Li acceptor dopants lead to hard piezoceramics and aging phenomena. Aged BT:Co, Li exhibits double loops and a distorted hysteresis cycle for nonpoled and poled ceramics, respectively. Ceramics poled by the increasing field process at room temperature and the field cooling process present different poled and aged states, which are dependent on the thermal history and poling process. The distorted hysteresis loops for BT:Co, Li indicate an increased internal bias field with aging time. Insertion of donor dopants, such as Nb5+ ions, significantly reduces the internal field. These behaviors are related to the presence of defect dipoles ($\text{M}_{\text {Ti}}$ ”– $\text{V}{_{\mathrm {O}}} {^{\circ }} {^{\circ }})^{x}$ due to the insertion of acceptor dopants in the B-sites following the oxygen vacancies to equilibrate charge compensation. BT:Co sintered with LiF leads to a quasi-symmetric hysteresis loop, indicating that F− may insert into an oxygen site and counteract the formation of oxygen vacancies. Dielectric drift of BT:Co, Li shows resilience to an ac electric field, which is related to the increased internal field. BT doped with 0.75 mol% Co2+/3+ and 1 mol% Li2CO3 presents hard piezoelectric behavior with a Rayleigh coefficient $\alpha = 2.53\,\,10^{-7}$ m/V and the capability to handle high electrical stress of up to 400 $\text{V}_{\text {rms}}$ /mm. [ABSTRACT FROM AUTHOR]

The study of nonlinear optical (NLO) materials is critical for the evolution of laser technology. AgBi(CrO 4) 2 crystallizes in the tetragonal lattice with a space group of I 4 ¯ is a potential candidate for the infrared (IR) region due to its high birefringence (Δn = 0.18@1064 nm), better NLO response than the KDP crystal, and relatively high electro-optical coefficients. The elastic constant of AgBi(CrO 4) 2 is ductile, and the high piezoelectric coefficients make this crystal attractive as a bifunctional material. [ABSTRACT FROM AUTHOR]

In order to improve the robustness and low-speed performance of continuous rotary electro-hydraulic servo system under influences of dynamic uncertainties, parametric perturbation, friction, other non-linear properties, and uncertainties, the robust control strategy was proposed with Adaboost prediction. Firstly, basing on the system mathematic model, the model with structured uncertainty and generalised state equation was established with parametric perturbation and external disturbances, and then the robust controller was developed by adopting [inline-formula] theory. Furthermore, Adaboost algorithm based on radial basis function (RBF) neural network was applied to design the system feedback mechanism, so the multiple weak neural network learners were obtained by using Adaboost algorithm to train system actual output and input. Also, these weak neural network learners constituted a strong learner to predict the electro-hydraulic servo system output and calculate the predictive error so as to adjust the system robust control output, so the real-time control was carried out by the robust controller. Some comparative simulated results are obtained to verify the proposed controller guarantees performances of low speed, tracking accuracy, and ability of anti-interference, which greatly expands the band of frequency response and improve the system robustness.

Abstract Nanostructured thin films of pure as well as Mg-doped Zinc Oxide (MZO) were successfully casted on glass substrates through sol-gel technique. X-ray diffraction patterns display that all deposited films exhibit good crystallinity, hexagonal wurtzite structure and are preferentially grown along (002) plane (i.e. C-axis). Surface morphology, vibrational modes and optical properties were inspected by AFM, FT-Raman and UV–Visible–NIR spectroscopy. AFM Analysis revealed the uniform nanowire growth of MZO films where each nanowire was made up of very fine nanoparticles. The grain size was found to be increased from 16 to 25 nm with increasing the Mg-doping which agreed with the crystallite sizes obtained from the XRD analysis. The linear and nonlinear optical functionals were evaluated from optical data. Further, the deposited films were subjected to Z-scan measurement and studied its different key properties. The values of χ (3) is found to be enhanced from 0.27 × 10−8 to 4.36 × 10−8 due to Mg doping. The optical limiting threshold of MZO nanostructured films are also studied, and the obtained threshold values are found in the range 1.7 to 7.4 kJ/cm2. These low values suggests that the fabricated films can be used as optical limiters to protect sensor devices from high intensity light. Graphical abstract Image 1 Highlights • Good quality MZO films were grown by sol-gel spin coating technique. • Structural and vibrational studies confirms their good crystalline nature. • The values of χ (3) is found to be enhanced from 0.27 × 10−8 to 4.36 × 10−8 by doping. • Optical limiting (OL) threshold are found in range of 1.7–7.4 kJ/cm2. • Low values of OL threshold suggests their use as guard to sensor devices. [ABSTRACT FROM AUTHOR]

The present paper deals on the investigation results of the detection of electromagnetic radiation in a glow discharge plasma of various gases. The voltage to the lamp is applied from a current source, providing a glow discharge in the lamp. It was shown that the detection efficiency depends strongly on the shape of the I-V characteristic of a gas-discharge lamp, as well as on the applied voltage (electric field). The different types of neon gas-discharge lamps were used as detectors. We also investigated the detection of a pulsed neodymium laser in air at an external electric field. Under the joint action of the laser pulse and the applied electric field, in the focusing region of the laser beam breakdown of air occurs. Thanks to the constant applied field, the created plasma behaves as a medium with a quadratic nonlinearity, which makes it possible to detect the electromagnetic radiation. [ABSTRACT FROM AUTHOR]

Abstract In this paper linear and nonlinear optical dielectric function of a slab of CdSe/ZnS quantum dot matrix associated with intersubband transitions is investigated theoretically. To this end, by using effective mass approximation and density matrix, the electronic structure and dielectric function of quantum dots are calculated. Afterwards, the Clausius-Mossotti relation and TKF model is used to calculate the effective dielectric function and susceptibility of slabs of ffc and randomly ordered quantum dots. The dependence of dielectric function, susceptibility, refractive index (RI) and absorption coefficient (AC) of the slab on the size and density of quantum dots have been studied. The results show that for all radii the AC and RI of fcc ordered quantum dots have higher magnitude than randomly ordered ones. It is also found that magnitude of the dielectric function of the slab increases by increasing radius and intensity. At fixed radii the dielectric function, RI and AC increases by increasing number density of quantum dots in the slab. Highlights • Slabs of randomly ordered quantum dots have lower absorption coefficient and refractive index than fcc ordered ones. • Dielectric function experience a red shift by increasing radius at fixed number density. • For a fixed radius, the absorption coefficient and refractive index of the slab increases by increasing number density. [ABSTRACT FROM AUTHOR]

Abstract Numerical verification is presented for modelling the magnetic effect of concrete structures reinforced with steel rebar. The model is based on the filling factor concept and takes into account magnetic anisotropy associated with the rebar pattern. Test problems are solved that prove applicability of the model in case of nonlinear properties of the reinforcement steel. A nonuniform field distribution is studied for a reinforced structure with an internal field source. Accuracy of simulated field maps with high gradients near ends of modelled structures has been assessed. The model has been verified in comparative computations with the use of other models. As an example, the proposed approach has been applied to a simplified magnetic model of the ITER tokamak complex. Then fields perturbations associated with the tokamak building structures have been evaluated for the gas breakdown at plasma initiation. [ABSTRACT FROM AUTHOR]

Solid state solution AgGaGe 3(1–x) Si 3x Se 8 in the range of x = 005–030 were synthesized and absorbance, FTIR, Raman spectroscopy, second harmonic generation measurements has been performed to explore linear and non-linear optical features The measured SHG intensity demonstrate significant dependence of non-linear optical properties from silica content. Analysing of Urbach’s energy and Raman spectra allowed to determine the degree of defect depending on the chemical composition and temperature. [ABSTRACT FROM AUTHOR]

Owing to mixed‐integer and non‐linear properties, the distribution network reconfiguration (DNRC) problem has been widely addressed with meta‐heuristic algorithms. To accelerate the solution process, two essential components of meta‐heuristic algorithms are investigated in this study: solution representation and fitness evaluation. Instead of the popular binary and integer numbers, decimal encoding is employed. Decoding is based on the proposed probability‐based loop destruction strategy. The fitness evaluation is based on the power flow calculation of radial network. Different from backward/forward sweep method, the advantageous direct solution technique is utilised, where the matrix generation process has been accelerated. Both improvements are based on the graph theory and fully explained with illustrative examples. Case studies are implemented on five benchmark systems. The superiority of the proposed methods over their advanced counterparts has been established with intensive comparisons. Finally, these methods are integrated into a standard particle swarm optimisation framework for the solution of DNRC. Results indicate that the proposals significantly improve the solution efficiency without the loss of quality. [ABSTRACT FROM AUTHOR]

Quantum dots of zinc gallate (ZnGa 2 O 4 ) has been synthesized by wet chemical route at a temperature of 90 °C. The structural, linear and nonlinear optical properties of ZnGa 2 O 4 were investigated. Electronic band structure calculations are carried out for ZnGa 2 O 4 , using density functional approach and the electron effective mass, hole effective mass and band gap are evaluated as 0.27m e , 16.10m e and 4.58eV respectively, from which the exciton Bohr radius is estimated to be 2.72 nm. From transmission electron microscopy, size of cubic spinel ZnGa 2 O 4 quantum dots is obtained as 8.3 nm. The theoretical band gap for ZnGa 2 O 4 estimated using Brus equation is 4.6eV and it agrees with band gap assessed from diffuse reflectance measurements. The sample shows blue emission under UV excitation. Nonlinear optical characterization of ZnGa 2 O 4 is done using open and closed aperture z scan technique and it shows saturable absorption and self-defocusing behavior making it suitable for display and nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

Oxide varistors are made of inhomogeneous material whose properties are determined by active grain boundaries. It is essential that in the microstructure of a varistor only active grain boundaries are present as only such boundaries are involved in the process of conduction. Commercial varistors are characterized by a microstructure with a large amount of electrically inactive areas which include zinc-antimony spinel, bismuth oxide, and pores. Studies on elimination of inactive grain boundaries, which are the intergranular areas rich in reaction products of varistor components and pores, lead to an improvement in the microstructure, thereby improving the electrical properties of the varistor. The results were evaluated using statistical methods, defining the percentage of active grain boundaries in the varistor. Statistical analysis showed that the best results were obtained for a bismuth oxide varistor doped with antimony oxide, containing nearly 100 % conductive grain boundaries in its body. [ABSTRACT FROM AUTHOR]

A new alkali metal borate with formula Na 6 [B 4 O 5 (OH) 4 ] 3 . 8H 2 O single crystal has been grown by slow evaporation method under room temperature condition for the first time. The structural analysis reveals that the grown crystal crystallizes in the rhombohedral space group R32 with cell parameters a = 11.27 Å, b = 11.27 Å, c = 21.27 Å and α = β = 90°, γ = 120°. The intermolecular interactions of symmetric stretching of BO 3 and asymmetric stretching of BO 4 were identified by Fourier-transform infrared spectroscopy (FT-IR). Optical investigation on the hydrated borate shows that the material possessed a high transmittance of about 60% in the entire UV- visible region with an optical absorption edge at 220 nm and the band gap was found to be 4.972 eV. The theoretical calculations were performed in order to find the linear optical constant such as linear absorption coefficient, extinction coefficient and reflectance etc. Thermogravimetric (TG)/Differential scanning calorimetry (DSC) analysis for the grown crystal displayed that the material is stable up to 116 °C and having the melting point of 145 °C. The frequency independent dielectric constant and dielectric loss were performed at different temperature. AC conductivity was studied by means of electrical relaxation process and it is due to the presence of water molecules in the compound. The third order nonlinear susceptibility (χ 3 ), nonlinear refractive index (n 2 ) and the absorption coefficient (β) are found to be in the order of 1.36 × 10 −6 esu, 3.88 × 10 −8 cm 2 /W and 0.026 × 10 −4 cm/W respectively. The strong optical limiting behaviour of the material could be attributed to the two photon absorption mechanism and negative nonlinearity due to self-defocusing effect. [ABSTRACT FROM AUTHOR]