The maritime industry is a critical pillar of global trade, but it faces mounting pressure to improve operational cost-efficiency amid rising costs and stringent environmental regulations. This challenge is particularly acute in constrained environments, such as Iran, where sanctions and infrastructure limitations exacerbate inefficiencies. This study develops and applies a hybrid decision-making framework to identify and prioritize the key drivers of operational cost-efficiency in Iran’s maritime sector. The framework integrates the adaptive fuzzy analytic hierarchy process (FAHP) to derive expert-based criterion weights under uncertainty with Bayesian Analysis and Markov Chain Monte Carlo (MCMC) simulations for robust probabilistic inference. Data were collected from 108 industry stakeholders across major Iranian ports. The results demonstrate that the adoption of blockchain technology (weight = 0.28), clean fuel solutions (0.25), advanced logistics optimization (0.22), and risk management mechanisms (0.25) are significantly associated with substantial perceived reductions in operational costs (15–30%) and carbon emissions (15–20%). Statistical and Bayesian validations confirmed all hypotheses with high posterior probabilities. The study provides a context-sensitive, evidence-based roadmap for strategic investment, prioritizing digital infrastructure and clean energy transition to navigate economic constraints and advance sustainability goals. The hybrid FAHP-Bayesian methodology provides a framework for complex decision-making in industrial environments.
We provide a unified theory, within the framework of the multi-phase Darcy description, on gravity current, interfacial and unsaturated flows in a vertically heterogeneous porous layer, which finds applications in many geophysical, environmental and industrial contexts. Based on the assumption of vertical gravitational-capillary equilibrium, a theoretical model is presented to describe the time evolution of the saturation field and the interface shape, imposing a general formula for the vertical distribution of intrinsic permeability, porosity and capillary entry pressure. Example calculations are then provided in the Cartesian configuration to illustrate potential implications of the theory, imposing power-law distribution of vertical heterogeneity. Seven dimensionless parameters are identified, which arise from the standard Darcy description of multi-phase flow and measure the influence of vertical heterogeneity, viscosity ratio, and the competition between gravitational and capillary forces. Four asymptotic regimes are recognised, representing unconfined unsaturated flows, confined unsaturated flows, unconfined interfacial flows and confined interfacial flows. The influence of heterogeneity is then discussed in the two unsaturated flow regimes based on the evolution of the interface shape, frontal location, saturation distribution, and the time transition between unconfined and confined self-similar flows.
Damien Bouffard, Tomy Doda, Cintia L. Ramón
et al.
The sloping boundaries of stratified aquatic systems, such as lakes, are crucial environmental dynamic zones. While the role of sloping boundaries as energy dissipation hotspots is well established, their contribution to triggering large-scale motions has received less attention. This review delves into the development of thermally driven cross-shore flows on sloping boundaries under weak wind conditions. We specifically examine ‘thermal siphons’ (TS), a dynamical process that occurs when local free convection transforms into a horizontal circulation over sloping boundaries. Thermal siphons result from bathymetrically induced temperature (i.e. density) gradients when a lake experiences a uniform surface buoyancy flux, also known as differential cooling or heating. In the most common case of differential cooling of waters above the temperature of maximum density, TS lead to an overturning circulation characterised by a downslope density current and a surface return flow within a convective environment. Field observations, laboratory experiments and high-fidelity simulations of TS provide insights into their temporal occurrence, formation mechanisms, water transport dynamics and cross-shore pathways, addressing pivotal questions from an aquatic system perspective. Fluid mechanics is a fundamental tool in addressing such environmental questions and thereby serves as the central theme in this review.
Giovanni Di Muccio, Simone Gargano, Domingo Francesco Iacoviello
et al.
Transport in nanofluidic devices is often characterized by complex electrohydrodynamic coupling. Electro-osmotic flow (EOF), i.e. the motion of fluid due to an external electric field, is one of the most common electrohydrodynamic phenomena. However, the classical continuum description of EOF cannot be directly applied at the nanoscale, and no generic experimental techniques exist to measure EOF for nanopores just a few nanometres in size. This led to the development of approximate approaches to express EOF through experimentally accessible quantities. The most popular one, derived by Gu et al. in 2003, employs nanopore selectivity measured via reversal potential experiments and expresses EOF as the sum of water molecules dragged by each ion moving through the pore. Here, combining theoretical arguments, continuum electrohydrodynamic and molecular dynamics simulations, we discuss the limitations of these approximations. Our results indicate that, although some approximate expressions contradict basic fluid dynamics scaling arguments, they still capture the order of magnitude of EOF for very narrow biological nanopores such as MspA, CytK and CsgG. Finally, we highlight some caveats of the method, particularly when dealing with non-cylindrical biological pores and the effects of localized alterations of the pore surface charge, such as point mutations commonly employed in nanopore sensing technology.
In the paper spaces of periodic functions of several variables were considered, namely the Lorentz space L2,τ(Tm), the class of functions with bounded mixed fractional derivative Wr2,τ, 1 ≤ τ < ∞, and the order of the best M-term approximation of a function f ∈ Lp,τ(Tm) by trigonometric polynomials was studied. The article consists of an introduction, a main part, and a conclusion. In the introduction, basic concepts, definitions and necessary statements for the proof of the main results were considered. One can be found information about previous results on the mentioned topic. In the main part, exact-order estimates are established for the best M-term approximations of functions of the Sobolev class Wr2,τ1 in the norm of the space Lp,τ2(Tm) for various relations between the parameters p,τ1,τ2.
In this paper, we study the rank characteristics for families of cubic theories, as well as new properties of cubic theories as pseudofiniteness and smooth approximability. It is proved that in the family of cubic theories, any theory is a theory of finite structure or is approximated by theories of finite structures. The property of pseudofiniteness or smoothly approximability allows one to investigate finite objects instead of complex infinite ones, or vice versa, to produce more complex ones from simple structures.
The study of syntactic and semantic properties of a first-order language, generally speaking, for incomplete theories, is one of the urgent problems of mathematical logic. In this article we study Jonsson theories, which are satisfied by most classical examples from algebra and which, generally speaking, are not complete. A new and relevant method for studying Jonson theories is to study these theories using the concepts of syntactic and semantic similarities. The most invariant concept is the concept of syntactic similarity of theories, because it preserves all the properties of the theories under consideration. The main result of this article is the fact that any perfect Jonson theory which are complete for existential sentences, is syntactically similar to some polygon theory (S-polygon, where S is a monoid). This result extends to the corresponding classes of Jonsson theories from the Jonsson spectrum of an arbitrary model of an arbitrary signature.
Natural ventilation can play an important role towards preventing the spread of airborne infections in indoor environments. However, quantifying natural ventilation flow rates is a challenging task due to significant variability in the boundary conditions that drive the flow. In the current study, we propose and validate an efficient strategy for using computational fluid dynamics to assess natural ventilation flow rates under variable conditions, considering the test case of a single-room home in a dense urban slum. The method characterizes the dimensionless ventilation rate as a function of the dimensionless ventilation Richardson number and the wind direction. First, the high-fidelity large-eddy simulation (LES) predictions are validated against full-scale ventilation rate measurements. Next, simulations with identical Richardson numbers, but varying dimensional wind speeds and temperatures, are compared to verify the proposed similarity relationship. Last, the functional form of the similarity relationship is determined based on 32 LES. Validation of the surrogate model against full-scale measurements demonstrates that the proposed strategy can efficiently inform accurate building-specific similarity relationships for natural ventilation flow rates in complex urban environments.
A new numerical method is proposed for solving the generalized Buckley-Leverett problem, which describes the movement of two-phase mixtures of Bazhenov bed sediments in a class of discontinuous functions. To this end, we introduce an auxiliary problem that has advantages over the main problem, and using these advantages, an original finite difference method to solve of the auxiliary problem is developed. Using the suggested auxiliary problem, a solution which expresses exactly all physical characteristics of the problem is obtained.
The main objective of this article is to provide the analytical solutions (not previously found and not available in the literature) of some problems related with definite integrals integrands of which are the products of the derivatives of Legendre’s polynomials of first kind having different order, with the help of some derivatives of Legendre’s polynomials of first kind Pn(x), Rodrigues formula, Leibnitz’s generalized rule for successive integration by parts and certain values of successive differential coefficients of (x2-1)r at x = ±1.
The paper deals with the second boundary value problem for the loaded heat equation in the first quadrant. The loaded term contains a fractional derivative in the Caputo sense of an order α, 2<α<3. The boundary value problem is reduced to an integro-differential equation with a difference kernel by inverting the differential part. It is proved that a homogeneous integro-differential equation has at least one non-zero solution. It is shown that the solution of the homogeneous boundary value problem corresponding to the original boundary value problem is not unique, and the load acts as a strong perturbation of the boundary value problem.
In this paper the stability of the initial value problem for the third order partial delay differential equation with involution is investigated. The first order of accuracy absolute stable difference scheme for the solution of the differential problem is presented. Stability estimates for the solution of this difference scheme are proved. Numerical results are provided.
Water wave resonance between two side-by-side vessels is a multimode resonant hydrodynamic phenomenon with low damping. The potential flow damping and viscous damping inside the gap play a significant role, influencing the amplitudes of the gap resonances. The frequencies of the gap modes can be well predicted by linear potential flow theory, while much effort has been made to explore the nature of the viscous damping. A series of experiments is conducted to explore the temporal (Zhao et al., Journal of Fluid Mechanics, vol. 812, 2017, 905–939) and spatial structure (Zhao et al., Journal of Fluid Mechanics, vol. 883, 2020, A22) of the resonant responses along the gap. Ultimately, it is of practical interest to understand the response statistics along the gap in random seas, to facilitate decision making for safe offshore operations. Following our previous studies which focused on new physics, here we identify the design waves that produce the most probable maximum responses under unidirectional random linear wave excitation. This is achieved through an efficient prediction model within linear theory. Combining the experimental data and linear potential flow calculations, we provide the lower and upper bounds of gap responses, bracketing possible responses at field scale. The statistical model is expected to be of practical importance for offshore operations.
High accuracy analytic functions have been determined for the ground state eigenvalue of the quantum anharmonic potential x4+λx6. The procedure here used is a new application of the multipoint quasi-rational approximation method (MPQA) to quantum mechanics. Previous applications of the technique were performed in the case where the eigenvalues of the potential were already known for the particular case of λ=0. The extension of the method, where this condition is not accomplished, is presented here. As a first step, power and asymptotic expansions have been now also determined. This is followed by the search of a bridge function connecting both expansions, and later the determination of the parameters. Accuracies smaller than 0.1% have been found with only nine parameters.
Arjun Sharma, Irina I. Rypina, Ruth Musgrave
et al.
Inverting an evolving diffusive scalar field to reconstruct the underlying velocity field is an underdetermined problem. Here we show, however, that for two-dimensional incompressible flows, this inverse problem can still be uniquely solved if high-resolution tracer measurements, as well as velocity measurements along a curve transverse to the instantaneous scalar contours, are available. Such measurements enable solving a system of partial differential equations for the velocity components by the method of characteristics. If the value of the scalar diffusivity is known, then knowledge of just one velocity component along a transverse initial curve is sufficient. These conclusions extend to the shallow-water equations and to flows with spatially dependent diffusivity. We illustrate our results on velocity reconstruction from tracer fields for planar Navier–Stokes flows and for a barotropic ocean circulation model. We also discuss the use of the proposed velocity reconstruction in oceanographic applications to extend localized velocity measurements to larger spatial domains with the help of remotely sensed scalar fields.
A quasilinear autonomous system with an operator of differentiation with respect to the characteristic directions of time and space variables associated with a Lyapunov’s vector field is considered. The question of the existence of multi - periodic solutions on time variables is investigated, when the matrix of a linear system along characteristics has the property of exponential stability. And the non - linear part of the system is sufficiently smooth. In the note, on the basis of Lyapunov’s method, the necessary properties of the characteristics of the system with the specified differentiation operator were substantiated; theorems on the existence and uniqueness of multi - periodic solutions of linear homogeneous and nonhomogeneous systems were proved; sufficient conditions for the existence of a unique multi - periodic solution of a quasilinear system were established. In the study of a nonlinear system, the method of contraction mapping was used.
In this paper the question on unconditional basicity of the system of eigenfunctions of the involutive perturbed Sturm-Liouville operator is investigated. The Green’s function of the operator under consideration in the case of constant coefficients is constructed. The estimates of the Green’s functions are obtained. The existence of the Green’s function is shown in the case when the operator under consideration has a variable coefficient. The theorem on the equiconvergence of expansions with respect to the eigenfunctions of the indicated operators is proved with the help of the Green’s function. The basicity of the eigenfunctions of the operator under consideration in the class L2(−1, 1) is proved. It is established that the basis from the
eigenfunctions of the involutive perturbed Sturm-Liouville operator is the unconditional basis.
Смоделирована динамика упруго - деформируемых плоских и пространственных механизмов. Построены матрицы, описывающие инерционные, диссипативные и жесткостные свойства элементов при действии внешних сил, сил инерции, дополнительных узловых сил. Полные перемещения при этом описаны суммой деформационных и кинематических перемещений. Разработаны алгоритм и комплекс вычислительного пакета прикладных программ на основе разработанных подходов, методической основы для многовариантных компьютерных расчетов сил, динамического напряженно - деформированного состояния в элементах упругих механизмов. Используемый в работе метод конечных элементов дает возможность для многовариантных расчетов напряженно - деформированного состояния механизмов, для установления закономерности распределения упругих перемещений, внутренних усилий, напряжений в зависимости от многочисленных факторов, т.е. упругих свойств, параметров движения, внешних статических и переменных во времени сил.