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We conduct systematic studies of the optical characteristics of plasmonic nanoparticles that exhibit C2v symmetry. In particular, we analyze three distinct geometric configurations: an L-type shape, a crescent, and a split-ring resonator shaped like the Greek letter π. Optical properties are examined using the finite-difference time-domain method. It is demonstrated that all three shapes exhibit two prominent plasmon modes associated with the two axes of symmetry. This is in addition to a wide range of resonances observed at high frequencies corresponding to quadrupole modes and peaks due to sharp corners. Next, to facilitate nonlinear analysis, we employ a semiclassical hydrodynamic model, where the electron pressure term is explicitly accounted for. This model goes beyond the standard Drude description and enables capturing nonlocal and nonlinear effects. Employing this model enables us to rigorously examine the second-order angular resolved nonlinear optical response of these nanoparticles in each of the three configurations. Two pumping regimes are considered, namely, continuous wave (CW) and pulsed excitations. For CW pumping, we explore the properties of the second harmonic generation (SHG). Polarization and angle-resolved SHG spectra are obtained, revealing strong dependence on the nanoparticle geometry and incident wave polarization. The C2v symmetry is shown to play a key role in determining the polarization states and selection rules of the SHG signal. For pulsed excitations, we discuss the phenomenon of broadband terahertz (THz) generation induced by the difference-frequency generation. It is shown that the THz emission spectra exhibit unique features attributed to the plasmonic resonances and symmetry of the nanoparticles. The polarization of the generated THz waves is also examined, revealing interesting patterns tied to the nanoparticle geometry. To gain deeper insight, we propose an analytical theory that agrees very well with the numerical experiments. The theory shows that the physical origin of the THz radiation is the mixing of various frequency components of the fundamental pulse by the second-order nonlinear susceptibility. An expression for the far-field THz intensity is derived in terms of the incident pulse parameters and the nonlinear response tensor of the nanoparticle. The results presented in this work offer new insights into the linear and nonlinear optical properties of nanoparticles with C2v symmetry. The demonstrated strong SHG response and efficient broadband THz generation hold great promise for applications in nonlinear spectroscopy, nanophotonics, and optoelectronics. The proposed theoretical framework also provides a valuable tool for understanding and predicting the nonlinear behavior of other related nanostructures. [ABSTRACT FROM AUTHOR]

Negative Poisson's ratio in auxetic structures plays a crucial role in energy absorption and impact mitigation. Origami-based lattices within the realm of auxetic structures offer the advantage of facile fabrication and design. Nevertheless, the utilization of periodic lattices in origami-based auxetic structures constrains the available design space for achieving diverse mechanical properties. Addressing this limitation, our study introduces origami-based auxetic structures with functionally graded thickness, utilizing origami-based lattices known as Tachi–Miura polyhedra. We investigated the impact of functionally graded thickness on buckling behavior and force responses through dynamic loading experiments employing 3D-printed test pieces. The experimental results indicate that functionally graded thickness induces partial auxetic deformation in lattices, and the resulting nonsymmetric deformation prevents global buckling, thereby averting bounded forces observed in structures with uniform thickness. These findings extend the applicability of auxetic structures, spanning from energy absorption to the design of cushioning structures. [ABSTRACT FROM AUTHOR]

The Kadomtsev–Petviashvili (KP) equations are nonlinear partial differential equations which are widely used for the modeling of wave propagation in hydrodynamic and plasma systems. This study aims to make a valuable contribution to the literature by providing new solitary waves to the (2+1)- and (3+1)-dimensional potential Kadomtsev–Petviashvili (pKP)-B-type Kadomtsev–Petviashvili (BKP) equations. For this, the auxiliary equation method associated with Bernoulli equation is used and new solutions for the considered equations are obtained. The stability of obtained solutions is demonstrated using nonlinear analysis. It is shown that this method for the considered pKP–BKP equations is an important step forward in an overall mathematical framework for similar equations. [ABSTRACT FROM AUTHOR]

This study delves into the existence, uniqueness, and stability of solutions for a nonlinear coupled system incorporating mixed generalized fractional derivatives. The system is characterized by ψ-Caputo and ϕ-Riemann-Liouville fractional derivatives with mixed boundary conditions. We provide essential preliminaries and definitions, followed by a detailed analysis using fixed point theory to establish the main results. Furthermore, we discuss the Hyers-Ulam stability of the proposed system and illustrate the theoretical findings with several examples. This study extends and generalizes various results in the literature and provides new insights into the qualitative behavior of fractional differential systems. [ABSTRACT FROM AUTHOR]

A novel vibratory thru-feed rolling process for involute splined shaft was proposed and validated on a prototype equipped with a resonant module. The effects of lubricating medium, vibration frequency, and vibration amplitude on axial load were investigated. Through experimental analysis with the nonlinear surface fitting method, the optimum process parameters were determined to be a vibration frequency of 41 Hz, amplitude of 0.5 mm, and oil lubrication. An additional experimental validation was performed under these optimal conditions, resulting in a 39.06% reduction in axial load compared to the condition with neither vibration nor lubrication. Furthermore, the dimensional accuracy and mechanical properties were still within the requirements. Specifically, the grain size was refined by 56.54%, residual compressive stress increased by 143%, and hardness improved by 31%. [ABSTRACT FROM AUTHOR]

This study introduces a new method for nonlinear structural analysis of buildings using high-order Hermitian interpolation function matrices for Timoshenko elements. This method aims to improve the accuracy of traditional beam-column finite element analyses by using higher-order shape function polynomials. Thus, a p-adaptive procedure is employed to address the potential issues of increased complexity and round-off error associated with higher-order functions. The study uses a technique for removing outliers in the p-adaptive method, which is more consistent with the theoretical approach. Moreover, a novel strategy based on the generalized alpha method is applied to reduce even more convergence problems, allowing its parameters to adapt in each instant of the time-history analysis. These adaptive parameters permit setting a low tolerance error and avoiding changing these parameters manually in time-consuming analyses. The efficiency of using fourth-order beam-column elements is also investigated. Finally, the importance of the proposed method is demonstrated through examples of building analyses, which is the base of a proposed software called MainModelingStr. [ABSTRACT FROM AUTHOR]

This research presents a simplified approach using a uniaxial restoring force model to analyze the seismic response of recycled aggregate concrete (RAC) frames. Nonlinear simulations were conducted to explore how factors like axial compression ratio, reinforcement ratio, and cross-sectional geometry affect the ductility and seismic performance of RAC sections. The findings reveal that a reduction in the axial compression ratio from 0.60 to 0.57 results in a 15% increase in ductility, while a higher reinforcement ratio leads to a 20% enhancement. In addition, rectangular sections were found to be more sensitive to variations in material strength than square sections, offering key insights for structural optimization. The method proposed here also enhances computational efficiency by minimizing resource consumption and improving the convergence of nonlinear iterative procedures. These findings provide a theoretical foundation for optimizing the design and seismic evaluation of RAC structures, promoting their broader application in engineering practice. [ABSTRACT FROM AUTHOR]

The secure condition of the tunnel face perpetually remains as a matter of substantial concern throughout the execution of tunnel-construction endeavors. Especially in composite formations, the presence of longitudinal stratigraphic interfaces makes it an exceptionally complicated issue. An improved segmented three-dimensional collapse mechanism was constructed to account for the effects of lithological mutations on the face instability characteristics of tunnels. Then, the critical support pressure was evaluated in the context of kinematic limit analysis and the nonlinear Hoek-Brown failure criterion. The validity of the proposed model was confirmed by comparison with numerical simulations and theoretical results from literature. The impact of the distance between the tunnel face and the stratigraphic interface (L), the tunnel diameter (d), and the Hoek-Brown parameters on the support pressure and collapse mode were analyzed further. The results indicate that the face stability is predominantly determined by the geological parameters of the fractured rock mass and exhibits a consistent decrement with the increase of both L and d. A decline in the geological strength index (GSI), material constant (m i) and uniaxial compressive strength (σ ci), or an escalation in the disturbance factor (D) of the fractured rock mass results in an increase in the critical support pressure and an expansion of the potential failure range. [ABSTRACT FROM AUTHOR]

Systems designed for nonlinear vibration isolation that incorporate chaotic states demonstrate superior capabilities in vibration attenuation, adeptly modulating the spectral constituents of vibrational noise. Yet, the challenge of eliciting low-amplitude chaotic dynamics and perpetuating these states across a diverse array of parameters remains formidable. This study proposes a pioneering strategy and technique for modulating the chaos band by incorporating a time-delayed feedback control mechanism within the framework of nonlinear vibration isolation systems.The investigation commences with an exhaustive analysis of the nonlinear dynamics, shedding light on the principles dictating the evolution of chaos. The study then advances to scrutinize the dynamics of systems with delays to elucidate the chaos-inducing processes engendered by feedback with temporal lags. Building upon the system's responses, the chaotic performance and the effectiveness of the vibration isolation are crafted. Consequently, the time-delayed feedback control parameters are identified as pivotal design variables, which are then employed to dissect the control mechanisms influenced by the time-delayed feedback on the chaos band. Utilizing the delineated control mechanism, the nonlinear vibration isolation system is precipitously transitioned from a state of stable periodicity to one of chaos, fostering low-amplitude chaotic dynamics across an expansive parameter space, and in turn, resolving the previously stated challenge. Perhaps most significantly, the mechanism for attaining low-amplitude chaos introduced here paves the way for innovative methodologies in the active vibration isolation design of similar systems. Furthermore, it is anticipated to yield theoretical guidance for the manipulation of chaos bands and the formulation of active vibration isolation strategies within the domain of nonlinear vibration isolation systems. [ABSTRACT FROM AUTHOR]

In this paper, we consider the semilinear Dirichlet problem (P ε) : − Δ u + V (x) u = u n + 2 n − 2 − ε , u > 0 in Ω , u = 0 on ∂ Ω , where Ω is a bounded regular domain in R n , n ≥ 4 , ε is a small positive parameter, and V is a non-constant positive C 2 -function on Ω ¯ . We construct interior peak solutions with isolated bubbles. This leads to a multiplicity result for (P ε) . The proof of our results relies on precise expansions of the gradient of the Euler–Lagrange functional associated with (P ε) , along with a suitable projection of the bubbles. This projection and its associated estimates are new and play a crucial role in tackling such types of problems. [ABSTRACT FROM AUTHOR]

In this article, we consider the incompressible limit of global-in-time strong solutions with arbitrary large initial velocity for the compressible viscoelastic fluids in the sense of critical Besov framework. We decouple our compressible system into two coupling sub-systems by introducing a skew symmetric matrix, which is related to the deformation tensor. This work generalizes the similar result obtained by Hu et al. (Incompressible limit for compressible viscoelastic flows with large velocity, Advances in Nonlinear Analysis 12 (2023), 20220324) to the critical functional space with respective to the natural scaling of the system. The proof relies on the dispersive property of the linear system on the high-frequency regime and the parabolic property on the low-frequency regime. The dispersion tends to disappear when λ tends to infinite, but having large λ provides strong dissipation on the potential part of the velocity and thus makes the flow almost incompressible. In addition, by exploiting the intrinsic structure of the viscoelastic system, we obtain the global uniform estimates of the solutions near equilibrium. [ABSTRACT FROM AUTHOR]

Thin structures like shells are highly susceptible to mechanical instabilities. They can undergo large nonlinear elastic deformations while exhibiting combined bending and stretching modes of deformation. Here, we propose a new displacement-based finite element (FE) formulation based on the isogeometric discretization of Koiter's nonlinear shell theory and use of the method of dynamic relaxation (DR) to solve equilibrium configurations of problems involving fine-scale and hierarchical wrinkling and buckling. No imperfection seeding is required to trigger instabilities. The use of the NURBS basis provides a rotation-free, conforming, higher-order spatial continuity such that curvatures and membrane strains can be computed directly from interpolating the position vectors of the control points using spatial finite differences. The pseudo-dissipative FE dynamical system is updated through explicit time integration and made scalable for parallel computing using a message passing interface (MPI). The proposed FE method is successfully benchmarked against several numerical and experimental results. [ABSTRACT FROM AUTHOR]

A burgeoning literature emphasises the role of favourable external conditions and institutional design as key drivers of the survival of intergovernmental organisations. This article focuses on institutional overlap as a hitherto overlooked determinant of IGO survival. Studies on institutional complexity posit that overlap – the extent to which organisations perform similar tasks to address similar problems for some common members – may decrease the survivability of IGOs due to rule conflicts, institutional paralysis, and competitive pressures for limited resources. Contrary to this perspective, this article argues that greater overlap increases the likelihood of IGO survival for two reasons. First, similar IGOs will survive as member states use them to pursue forum-shopping strategies. Second, overlap enables IGO secretariats to draw on networks of support from other IGOs, rendering organisations that densely overlap with others more resilient. To test these propositions, the article combines data on institutional overlap in global governance and the survival of the 534 IGOs contained in the Correlates of War IGO dataset. Non-linear regression analysis finds that where organisations overlap more with existing organisations in terms of governance tasks and issue areas, the likelihood of IGO survival increases. Further analysis suggests that this result is driven by the forum-shopping strategies of powerful member states. Given that contemporary world politics is governed by an increasingly dense network of IGOs, these results hold important implications for the study of IGO survivability and the evolution of global governance more broadly. [ABSTRACT FROM AUTHOR]

The partitioning of masonry buildings in Structural Units (SUs), or aggregate of Structural Units, is a useful tool to simplify the analysis of the buildings and the study of static and seismic vulnerability. However, this allocation is affected by uncertainties, simplification, and sometimes unavoidable miscalculation due to the directionality of this subdivision. This procedure exposes the results to discrepancies due to the way the building is divided. The Castle of Rosignano is emblematic. In this paper, the dependence of the results on how the Structural Units are considered is analyzed, as well as the role of structural in plan and elevation irregularities on various SUs and their combination. Non-linear static analysis corresponding to different distributions of the building in Structural Units, the uncertainties about material properties, and different directions of the seismic action are analyzed, and the respective results are discussed here. A simplified approach, for the study of aggregate buildings on an urban scale, is based on the so-called "tabular method". Several Authors proposed and improved similar methods applied to different urban contexts. A comparison of simplified methodologies with the results of the detailed FEM analysis is also discussed and presented here. Finally, a simplified approach is proposed based on the regularity parameter of the building in aggregate. Taking the evidence from FEM analysis as a physical-mechanical base, the authors propose the quantitative definition of irregularity parameters and the use of them to determine the building vulnerabilities. The proposed procedure aimed to be a practical tool to determine, in an expeditious manner, the seismic capacity of a masonry building in aggregate. The model proposed in this paper, applied to the case of the study of Rosignano Marittimo (a typical situation of aggregate building in a historical context in Tuscany, Italy) shows emblematic results that can be extended to analogous configuration. [ABSTRACT FROM AUTHOR]

Seismic fragility analysis (SFA) is known as an effective probabilistic-based approach used to evaluate seismic fragility. There are various sources of uncertainties associated with this approach. A nuclear power plant (NPP) system is an extremely important infrastructure and contains many structural uncertainties due to construction issues or structural deterioration during service. Simulation of structural uncertainties effects is a costly and time-consuming endeavor. A novel approach to SFA for the NPP considering structural uncertainties based on the damage state is proposed and examined. The results suggest that considering the structural uncertainties is essential in assessing the fragility of the NPP structure, and the impact of structural uncertainties tends to increase with the state of damage. Subsequently, machine learning (ML) is found to be superior in high-precision damage state identification of the NPP for reducing the time of nonlinear time-history analysis (NLTHA) and could be applied in the damage state-based SFA. Also, the impact of various sources of uncertainties is investigated through sensitivity analysis. The Sobol and Shapley additive explanations (SHAP) method can be complementary to each other and able to solve the problem of quantifying seismic and structural uncertainties simultaneously and the interaction effect of each parameter. [ABSTRACT FROM AUTHOR]