Search Results (2,888)

The wave train generated by a moving vessel remains a persistent challenge in ship hydrodynamics, particularly in stratified oceans where internal waves contribute significantly to drag. This research investigates steady interfacial wave generation by flow past a semi-infinite curved plate in a two-layer fluid where both layers are of finite depth. Previous studies were limited by flat-plate geometries and infinite-depth approximations, neglecting the critical role of applied pressure as a design variable. We address these limitations to facilitate the engineering goal of wave drag reduction through optimal hull and pressure configurations. Using a scalar Wiener–Hopf formulation, we construct an analytical solution where the kernel is factorized via Cauchy-type integrals, bypassing the technical constraints of traditional infinite-product expansions. We derive a closed-form far-field amplitude and a wave-free condition, $M\left(\mu \right)=0$. This condition is a single complex equation, i.e., two independent real constraints. A one-parameter hull design can therefore generally only minimise the downstream wave amplitude; exact cancellation at linear order generally requires a second, independent real design freedom, such as a jointly optimised applied pressure. We quantify both regimes explicitly. Our findings demonstrate that physical stern flow patterns exhibit spatial relaxation and advection scales essential for energy transfer. This result provides a mathematically sharp framework for wave drag minimisation, quantifying the explicit performance trade-off between hull curvature and dynamic pressure control in stratified environments, and we are careful throughout to distinguish the formal linear theory cancellation from what is achievable with a single physically realisable (real-valued) design parameter. Full article

The quality factor is a key metric for evaluating the performance of micro-electro-mechanical and nano-electro-mechanical system resonators. Although reducing device dimensions enhances resonator sensitivity, it also intensifies energy dissipation, thereby degrading the quality factor. Among the dominant dissipation mechanisms in micro-/nano-resonators, support loss is strongly influenced by surface effects at small scales, particularly the surface elastic modulus and initial surface stress. In this study, support loss in a double-clamped micro-/nano-beam resonator with surface effects incorporated is investigated. A dynamic model incorporating the surface elastic modulus and initial surface stress is developed based on Euler–Bernoulli beam theory and Gurtin–Murdoch surface elasticity theory. A quality-factor calculation method is then established by combining elastic wave radiation in the supports with an energy-based formulation. The theoretical predictions are validated using a three-dimensional finite element model comprising the resonator with a surface layer, supports, and a perfectly matched layer. Further, the effects of the surface elastic modulus, initial surface stress, characteristic size, and dimensionless geometric parameters on support loss are examined. The results show that the surface elastic modulus and initial surface stress increase support loss and reduce the quality factor, with the initial surface stress exhibiting the stronger influence. The influence of these parameters becomes more pronounced as the characteristic size decreases, and variations in the length-to-thickness and width-to-thickness ratios further modify their contribution to support loss. Mechanistically, surface effects alter the effective bending stiffness and axial force, thereby changing the dynamic loads transmitted to the supports and resulting elastic-wave radiation. These findings provide theoretical insights for the design of high-quality-factor micro-/nano-devices. Full article

Beveled edges are inevitably formed in micro AT-cut quartz mesa resonators (QMRs) during the photolithography process. This local geometric variation alters the thickness distribution and edge stiffness, which in turn affects the coupling between the primary thickness-shear mode and adjacent parasitic modes. To elucidate the mechanism, we establish a vibration analysis model for the micro AT-cut QMR with beveled edge profiles based on the first-order Mindlin plate theory. The coupling between thickness-shear and flexure is the focus of the investigation. The uniform thickness regions and the beveled edge region are expressed using analytical solutions and power series expansions, respectively. The eigenfrequency equation is then derived through the interface continuity and free boundary conditions. The theoretical frequency spectra show good agreement with finite element results so that the accuracy of the proposed analytical approach is validated. A mode coupling intensity index is constructed based on the discrete Fourier spectrum of the surface displacement in the mesa region, and a modal kinetic energy ratio is introduced to characterize the modal coupling. The influence of structural parameters on the spectral characteristics and mode coupling intensity is analyzed. The results indicate that mesa parameters mainly regulate the resonance frequency and energy trapping of the primary thickness-shear mode. In contrast, due to changes in flexure stiffness of the ends and the reflection angle of elastic waves, the beveled edge parameters affect the coupling intensity between the primary thickness-shear mode and parasitic modes. The optimized parameter combinations lead to low coupling states with nearly pure thickness-shear vibration, while the mesa- and bevel-length related low coupling intervals exhibit better fabrication robustness. Full article

Violence against nurses is a global occupational health and safety issue, yet instruments that assess nurses’ attitudes towards violence from patients and their relatives are limited. This methodological study involved the development and evaluation of the Nurses’ Attitudes Towards Violence by Patients and Patients’ Relatives Scale. In the qualitative phase, 39 nurses were interviewed in depth until data saturation was reached, generating a pool of 61 items. Content validity with 15 experts (CVI = 0.90) yielded a draft of 57 items. The original quantitative sample (N = 608) was randomly divided into exploratory (n = 304) and confirmatory (n = 304) subsamples. Principal axis factoring with ProMax rotation supported a 36-item, three-factor solution that explained 52.3% of the common variance. This solution comprised the following factors: perception and causes of violence (20 items); effects of violence (13 items); and response to violence (3 items). In the original confirmatory subsample, the final model with six theory-based residual covariances was subjected to WLSMV confirmatory factor analysis, showing an overall acceptable fit (χ²(585) = 1297.5, χ²/df = 2.22, CFI = 0.900, TLI = 0.892, RMSEA = 0.063 [90% CI 0.059–0.068], SRMR = 0.093). A robustness wave involving 45 additional nurses, conducted between 27 August and 2 September 2026, produced almost identical results when combined with the confirmatory subsample (n = 349). Supplementary analyses supported composite reliability and discriminant validity, and found that measurement invariance was supported across institution type, whereas findings regarding sex invariance were interpreted as preliminary. In the original sample of N = 608, Cronbach’s α was 0.943, 0.930 and 0.842 for the three factors, and 0.950 for the total scale. Two-week test–retest reliability was r = 0.976. The scale provides a multidimensional measure of nurses’ evaluative-attributional beliefs, perceived effects and responses to violence from patients and relatives. Full article

Unethical pro-organizational behavior (UPB) is gaining scholarly attention due to its harmful consequences, yet limited research explains how employees’ perceptions of leaders’ personality traits drive such behavior. Drawing on conservation of resources theory and the Narcissistic Admiration and Rivalry Concept, this study examined whether and how perceived leader narcissistic rivalry predicts employee UPB. We argue that leaders high in narcissistic rivalry devalue and exclude others, increasing workplace ostracism. Ostracism, in turn, depletes employees’ psychological resources and motivates UPB as a compensatory strategy. We further propose that underdog expectations amplify this effect by shaping employees’ interpretations of exclusion. Using a three-wave, time-lagged survey of 383 full-time employees in South Korea and analyzing data with PROCESS Macro, results show that perceived leader narcissistic rivalry positively predicts workplace ostracism. Workplace ostracism increases UPB and mediates the relationship between leader narcissistic rivalry and UPB. Moreover, underdog expectations strengthen the positive association between ostracism and UPB, with stronger effects among employees high in such expectations. These findings identify workplace ostracism as a key resource-depletion mechanism linking leader narcissistic rivalry to unethical behavior and highlight underdog expectations as an important boundary condition. They highlight the need to manage narcissistic leadership, reduce ostracism, and strengthen ethical norms. Full article

Although perfectionism has received considerable attention from organizational scholars, research on how it enhances employee creativity remains limited. Drawing on the model of proactive motivation and trait activation theory, this study investigates the relationship between employees’ self-oriented perfectionism and creativity (including both radical and incremental creativity), with job crafting as a mediating mechanism. In addition, we incorporate work stress as a moderator and propose a moderated mediation model. Multi-wave survey data were collected from employees in several Chinese organizations. The results show that self-oriented perfectionism is positively associated with both radical and incremental creativity, and that job crafting mediates these relationships. Furthermore, work stress moderates the mediated relationships, such that the positive indirect associations are stronger when work stress is higher. Theoretical and practical implications are discussed. Full article

The spectral line density of an optical frequency comb (OFC) generated in a microring resonator is fixed by the free spectral range (FSR), and hence by the resonator size: the dense combs required for spectroscopy, optical clocks, and high-capacity communications conventionally demand centimeter-scale cavities, in direct conflict with photonic integration. Here, we propose a route around this FSR–footprint trade-off using topological ring resonators (TRRs) built on a silicon valley photonic crystal (VPC) platform. Evanescently coupling two identical TRRs, an optical analog of quantum tunneling in a double-well potential, deterministically splits each resonance into a doublet of supermodes (Rabi splitting), doubling the spectral line density within a fixed bandwidth while the parallel two-ring layout occupies orders of magnitude less chip area than a single conventional ring of equivalent effective FSR. A coupled-mode-theory model quantitatively captures the splitting observed in full-wave 3D finite-difference time-domain (FDTD) simulations, and the topological protection of the valley edge states preserves the doublet against lattice disorder; a fabrication-tolerance analysis shows the splitting varies by only a few percent for nanometer-scale gap errors. Nonlinear simulations based on the coupled nonlinear Schrödinger equation indicate that the doubled supermode grid translates directly into a denser comb, increasing the generated line count from 48 to 122 under identical Kerr-only pumping conditions. An explicit nonlinear-loss budget, including two-photon and free-carrier absorption, bounds these results for silicon at 1550 nm and identifies mid-infrared silicon and TPA-free platforms such as silicon nitride as physically realistic implementations. This design study establishes coupled topological resonators as a compact, disorder-tolerant architecture for high-density comb generation, which can potentially be experimentally demonstrated. Full article

While abundant evidence supports gratitude’s positive functions, recent findings have also revealed its potential to trigger aggressive behaviors. However, existing theories struggle to fully explain this apparent paradox. To address this gap, we introduce the construct of the gratitude mindset and explore its paradoxical impact on social behaviors. Study 1 (N = 221) employed an experiment to verify the distinct effect of the gratitude mindset on altruistic and aggressive behavior. Based on a three-wave survey, Study 2 (N = 462) revealed that a gratitude-is-enhancing mindset (GIEM) was positively associated with altruistic behavior and negatively associated with aggressive behavior, whereas a gratitude-is-inhibiting mindset (GIIM) was positively associated with aggressive behavior and negatively associated with altruistic behavior. Moreover, moral imagination partially mediated the effects of GIEM on altruistic behavior and aggressive behavior; moral disengagement partially mediated the effects of GIIM on altruistic behavior and aggressive behavior. These findings suggest that the gratitude mindset has both theoretical and practical relevance for understanding social behavior. Full article

This paper studies a coupled system of viscoelastic wave equations with frictional damping, cross-tempered fractional damping, viscoelastic memory, and logarithmic source nonlinearities. The fractional damping acts across the two components, so that the fractional feedback in each equation is generated by the velocity of the other component. To handle the memory and fractional terms, we introduce suitable history and diffusive variables and reformulate the problem as an evolution system in an extended energy space. Under appropriate assumptions on the relaxation kernels, fractional parameters, and nonlinear exponent, we establish the local well-posedness of mild and strong solutions using semigroup theory. We then use a potential-well argument to prove global existence for initial data in the stable set. Under an additional decay condition on the relaxation kernels, an appropriate Lyapunov functional is constructed to establish the exponential decay of the energy. Finally, numerical simulations based on a finite-difference scheme and a physics-informed neural network (PINN) are used to illustrate the predicted decay behavior. Full article

We investigate the non-linear dynamics of de Broglie gravitational waves within a post-Minkowskian framework. Starting from the perturbative solution proposed by Feoli and Scarpetta, we derive the second-order gravitational field generated by the wave’s self-interaction. Owing to the extremely high oscillation frequency of de Broglie gravitational waves, we employ the Isaacson/Misner–Thorne–Wheeler averaging procedure to obtain an effective coarse-grained geometry. The resulting averaged theory takes the form of an effective linear perturbation theory at second order in the wave amplitude. Near the symmetry axis, the resulting spacetime exhibits a non-vanishing static curvature generated entirely by non-linear effects. We show that geodesics in this effective geometry undergo bounded transverse oscillations governed by a harmonic equation. Possible implications for de Broglie’s wave–particle framework are also discussed. Full article

In maritime navigation, precise and stable ship course control is critical for operational efficiency and maritime safety, yet it is severely challenged by unpredictable marine disturbances (e.g., waves, wind, and currents) that consist of slowly varying and stochastic components. Traditional control methods, though effective under specific operating conditions, exhibit limited adaptability to the nonlinear, time-varying characteristics of marine systems and inherent dependence on accurate ship mathematical models, which easily leads to suboptimal performance and elevated navigation risks, especially under sudden and intense disturbances. To address these limitations, this study proposes a novel control strategy, namely, model-free control integrated with super-twisting sliding mode control (MFSTSMC) with a linear extended state observer (LESO), for enhanced ship course control. Derived from the ultra-local model, the proposed method integrates the simplicity and practicality of model-free control, the real-time disturbance estimation and compensation capability of LESO, and the strong robustness of STSMC. The Lyapunov stability theory is rigorously employed to prove the stability of the entire control system, ensuring that the steady-state error converges to zero. Comparative analyses are conducted on an ocean ship verification platform, with strictly unified parameters for fairness. The comparative results evaluate the proposed method under three typical scenarios: course-keeping (small ±10° and large ±70° maneuvers), course tracking (low/high-frequency sinusoidal trajectories and high-frequency 20° abrupt change trajectory), and resistance to sudden escalating disturbances. The results demonstrate that the proposed MFSTSMC with LESO significantly outperforms existing controllers in terms of tracking accuracy, response speed, stability, and disturbance rejection capability. Its superior performance originates from the synergistic effect of real-time disturbance compensation and robust sliding mode compensation, which effectively mitigates the impact of model deviations and complex marine disturbances. This study provides valuable insights for the development of advanced marine navigation control strategies, and the proposed method exhibits promising engineering application prospects for ocean ship navigation in complex dynamic marine environments. Full article

I contend that physics should provide a coherent account of reality, in addition to being an efficient algorithm for the prediction of empirical results. This article offers pictures of reality derived from theories of modern physics. In particular, it is shown that Bose quantum fields may be interpreted as pure wave fields via the Weyl–Wigner representation, the most relevant result being the existence of a stochastic vacuum field corresponding to the quantum vacuum fluctuations of the standard, canonical, formulation of field theory. That field provides explanations for the particle (photons) behavior of the electromagnetic field. Also, a realistic interpretation is offered for interference experiments with actual particles, like atoms. The interpretation of classical general relativity is standard but emphasis is given to the principle of equivalence. Problems like spacetime singularities (black holes) and the empirical violation of Bell inequalities are touched on but slightly. Asides from these problems, the main incompleteness of the article is the absence of a realistic interpretation of Fermi fields. Full article

Hydride perovskites have emerged as promising multifunctional materials for sustainable energy technologies owing to their potential for hydrogen storage and thermoelectric energy conversion. However, despite recent theoretical studies on tin-based hydride perovskites, a comprehensive understanding of the relationship between their structural, electronic, mechanical, thermoelectric, and hydrogen-storage properties remains limited. In this work, a systematic first-principles investigation of cubic XSnH₃ (X = Rb, Cs) hydride perovskites was performed using density functional theory within the full-potential linearized augmented plane wave (FP-LAPW) method, combined with Boltzmann transport calculations. The optimized structural parameters are in excellent agreement with previously reported theoretical data, confirming the reliability of the adopted computational approach. Both compounds satisfy the mechanical stability criteria and exhibit metallic electronic behavior dominated by Sn-p states around the Fermi level. The calculated thermoelectric properties reveal that the electrical conductivity decreases with increasing temperature, whereas the electronic thermal conductivity, power factor, and thermoelectric figure of merit increase continuously over the investigated temperature range. Among the studied compounds, RbSnH₃ exhibits superior thermoelectric performance together with a higher gravimetric hydrogen content (1.45 wt%) than CsSnH₃ (1.18 wt%). These findings demonstrate that alkali-metal substitution provides an effective strategy for tailoring the multifunctional properties of hydride perovskites and identify RbSnH₃ as a promising candidate for future hydrogen-storage and thermoelectric energy-conversion applications. Full article

Pile foundations transmit structural loads to deeper subsoil strata whenever the soil in the vicinity of the ground surface lacks sufficient strength and stiffness to ensure an adequate factor of safety against ultimate failure or warrant settlements to remain below acceptable limits. In many in situ conditions, piles are embedded in layered subsoil medium. In several circumstances, piles are subjected to tensile loading. Large and high-rise civil infrastructure subjected to wind loading, transport infrastructure under horizontal loading due to moving vehicles, offshore structures withstanding wind and wave loading, underground structures subjected to hydrostatic pressure due to buoyancy, etc., are some examples where tension loads are imparted on the supporting piles. The imparted uplift loads in these tension piles are balanced by the negative skin friction induced at the pile–soil interface. In this paper, an analytical model using systematic application of established upper bound shear stress theory to three-layered soil configurations has been developed to formulate the ultimate uplift capacity of tension piles in three-layered soil. The model adopted appropriate correlations for upper bound interface shear stresses in different soils as well as tensile failure of pile material itself. The developed solution was validated by comparing with available experimental results. Thereafter, a case study was performed to study the influence of the variation of pile geometries and relative stiffness on ultimate uplift capacities. Important conclusions were drawn from the entire study. Full article

Oikos (οἶκος, home) is a concept that split in modernity as it became “eco”: the oikos of economics and of ecology (quantification versus study of our home). In this essay, both derivations will be touched upon since the quantification of our natural home (econometrics) is arguably the modern source of the current climate crisis, while its study (ecology) claims to name that crisis—the Anthropocene—in order to begin to cure it. What role can art history play in this agonistic drama? There is already an architectural history (as in Reyner Banham’s Los Angeles of “Four Ecologies,” 1971). Art history, too, has ecological frameworks from the 1970s that need to be unearthed; this essay argues that they must necessarily be tied to economic ones. We get no ecological art history without the social history of art. Economic relations are found in art that represents or enacts human cultural patterns of extraction (what Marx himself identified as an “irreparable rift”); parallel ecological perceptions follow the Humboldtian logics of geographical niches hosting specifically local forms of life. Art history emerged as a discipline to deal with both these modes. It is coeval with the naming of “ecology,” and its many relations to the oikos deserve to be engaged. In three acts, this brief essay charts a dramatic arc from extraction to relation, with ecology as mediation throughout. The first act looks at a significant moment in which the economic aspects of social art history were foregrounded in Michael Baxandall’s classic Painting and Experience (1972). Baxandall theorized the “experience” of capitalist reckoning as a visual practice conjoined to aesthetic valuation. Relatedly, the quality of ultramarine, visually assessed and theologically charged, was contractually bound to systems of extraction and trade. In the second act, the essay considers Earthworks artists such as Robert Smithson, and anti-Gestalt psychologists, from Anton Ehrenzweig to perception scientist James J. Gibson. Gibson’s 1979 book The Ecological Approach to Visual Perception created a second mode of approaching the oikos: as a set of productive visual “habits” formed by the human body interacting with affordances of the planet. Act Three builds a simultaneous expansion and refutation of Gibson, privileging the non-visual senses in relation to strange media objects that can be analyzed by an art historian—epistemologies departing from vision to embrace amodal senses as ways of knowing environmental disaster in the Anthropocene. This necessarily engages the cultural polemic of symbiontics. Crafted in response to the newest forms of BioArt, this new ecological theory of aesthetics draws on the philosophical category of ontics, viz, symbiontics: symbiosis as that which is. Defeating the isolation fostered in Western art (think of Dūrer’s exceptionally precise and utterly alienated 1504 Hare), the symbiontic art discussed in Act Three is fully entangled. These relational aesthetic gestures are radical—a word whose root is radix, literally, root. Symbiontics engage us in a revolution in rooted sensibility, taken up in art that is in reciprocity with life. Presenting a mutual interdependence, second-wave BioArt performs itself on a planet that is oikos—art in reciprocity with the more-than-human species that maintain this garden of a home. Full article