Set Of Boundary Conditions Research Articles

Assessing the Effects of Miedzyodrze Area Revitalization on Estuarine Flows in the Odra River

The estuarine section of the Odra River network is influenced by various phenomena that shape its hydrological regime. The Lower Odra region includes “Miedzyodrze,” an area between the main branches of the Odra River that was previously used for agriculture. However, due to a lack of maintenance in the 20th century, Miedzyodrze’s infrastructure suffered significant damage, resulting in blockages and channel shallowing. Previous models of the lower Odra River network overlooked Miedzyodrze’s hydrodynamic impact on flow. To address this, a study aimed to assess Miedzyodrze’s influence on flows within the network. Three computational scenarios were developed: one treating Miedzyodrze as an uncontrolled floodplain, another excluding it from the flow like past models, and a third incorporating the hydraulic capacity of selected Miedzyodrze channels with hypothetical restoration. The construction of the models involved extensive field research, including bathymetric surveys and an inventory of channels and structures. Challenges arose from legal and technical constraints during the research. The hydraulic network model was developed using Hec-Ras software and underwent calibration and verification processes for accuracy and reliability. The study focused on analyzing changes in water distribution, flow reduction along the East Odra, flow ratios at specific points, and downstream flow alterations based on different scenarios and the aperture extent of the Widuchowa weir. The conducted analyses and deductions validate the thesis proposed in this study that the potential process of channel dredging and renovation of the hydraulic infrastructure in Miedzyodrze will significantly influence the flow distribution within the lower Odra River network. The significant impact of the Międzyodrze area on water distribution in the lower course of the Odra River has been successfully demonstrated. Under specific hydrological scenarios, a potential increase in flow through the Międzyodrze area from approximately 10–100 m3/s to a range of 60–420 m3/s has been identified. This dynamic alteration of river flow exerts a pronounced influence on further water distribution within the entire river network. For the purpose of addressing the matter at hand within this study, the following procedures were undertaken: → analysis of characteristic flow regimes and states, → bathymetric measurements, → flow measurements at selected cross-sections, → construction of a numerical model of the river network, → model calibration, → formulation of a set of boundary conditions, → modeling, → results analysis.

Analytical Solution for One-Dimensional Transient Thermal Conduction in a Hollow Cylinder

The primary use of analytical solutions in the area of thermal conduction problems is for verification purposes, comparing the calculated temperatures and heat flux values to the results from numerical codes. The contribution from the analytical solutions can be especially significant where large temperature gradients are found. This is because the temperature and heat flux results can be found very precisely: normally to eight or 10 significant figures using analytical solutions. Normally, numerical solutions require extremely fine grids in high-heat-flux locations, but analytical solutions can provide insight into the adequacy of grid densities in these types of situations. One area of particular interest is in nonrectangular analytical solutions because generalized numerical grids do not naturally lend themselves well to curved surfaces without a large number of nodes. In this current study, four solutions are offered in a geometry involving a hollow cylinder. Two of the solutions examine heating from the inside of the cylinder, and two involve heating from the outside. Development of the solutions is provided along with results that show the temperature responses to the various sets of boundary conditions. A mathematical identity is used as part of the solution, which eliminates the need to evaluate an infinite series, along with need to find roots of transcendental equations and evaluate Bessel functions. Intrinsic verification is also applied in order to provide assurance that the solutions are properly formulated and evaluated.

A Review of Formulations, Boundary Value Problems and Solutions for Numerical Computation of Transcranial Magnetic Stimulation Fields.

Since the inception of the transcranial magnetic stimulation (TMS) technique, it has become imperative to numerically compute the distribution of the electric field induced in the brain. Various models of the coil-brain system have been proposed for this purpose. These models yield a set of formulations and boundary conditions that can be employed to calculate the induced electric field. However, the literature on TMS simulation presents several of these formulations, leading to potential confusion regarding the interpretation and contribution of each source of electric field. The present study undertakes an extensive compilation of widely utilized formulations, boundary value problems and numerical solutions employed in TMS fields simulations, analyzing the advantages and disadvantages associated with each used formulation and numerical method. Additionally, it explores the implementation strategies employed for their numerical computation. Furthermore, this work provides numerical expressions that can be utilized for the numerical computation of TMS fields using the finite difference and finite element methods. Notably, some of these expressions are deduced within the present study. Finally, an overview of some of the most significant results obtained from numerical computation of TMS fields is presented. The aim of this work is to serve as a guide for future research endeavors concerning the numerical simulation of TMS.

THE APPLICATION OF THE EXTENDED CELLS METHOD TO SIMULATE THE FLOW OF COMBUSTION GASES IN THE LPRE CHAMBER


 
 
 Abstract. The numerical modeling of the process of two-dimensional axisymmetric flow of combustion gases in the chamber of a liquid rocket engine is considered in this study. In general, when solving such problems, meshes are used which lines coincide with the boundaries of the computational domain. However, an alternative solution is proposed here, which is to apply the extended cells method. It allows using rectangular Cartesian grids, which lines do not coincide with the boundaries of the computational domain, without reducing the stability of the numerical solution due to the fractional finite volumes. This also simplifies the setting of boundary conditions in such volumes. The advantage of the proposed approach over the generally accepted one is the absence of the global geometric transformations during the entire modelling process, which leads to a reduction in its duration. To perform the numerical modelling, an inviscid ideal compressible gas of constant chemical composition was chosen as a basic model of a continuum. It is described by a system of the unsteady Euler equations in integral form, which was closed by the Mendeleev-Clapeyron equation of state. For the numerical solution of this system, the finite volume method was used with the reconstruction of the flow parameters by the WENO algorithm of the third order of accuracy. The solution of the Riemann problem was carried out using the Lax-Friedrichs relations. Time integration of the system of equations was performed using the explicit Runge-Kutta method of the third order of accuracy. All calculations were carried out on a uniform rectangular Cartesian mesh, which lines did not coincide with the boundaries of the computational domain. The results were compared with the solution of the same problem using the ANSYS Fluent on an unstructured mesh coinciding with the boundaries of the computational domain. The value of the relative error obtained as a result of comparing both solutions did not exceed 0.05.
 
 

Nonlinear radiation effects on water-based nanofluid containing CNTs subject to heat source/ sink past a wedge

In this paper, a two-dimensional and incompressible laminar flow comprised of water-based carbon nanotubes over convectively heated moving wedge under the magnetic field and nonlinear radiation and heat production/ absorption is investigated. The base nanofluid (water) contains single wall carbon nanotubes (SWCNTs) and multiple walls carbon nanotubes (MWCNTs). In order to convert the dimensional nonlinear partial differential equations in nondimensional nonlinear ordinary differential form, an adequate set of similarity variables had been used. These set of equations and boundary conditions are evaluated by the implementation of RKF-45 (Runge–Kutta–Fehlberg fourth-fifth) order scheme. The influence of several physical parameters on particular nanoparticle’s volume friction, temperature and velocity ratio parameter, heat source/ sink parameter, nonlinear radiative constraint, exponent constant, magnetic factor, Eckert and Biot numbers is studied. An opposite behavior of volume fraction and velocity ratio parameters on velocity and energy profiles is achieved.

Environmental impact of process constrained topology optimization design on automotive component’ life

The components’ lightweighting has been pursued, especially in the transport industry, for greenhouse gas reduction. Topology optimization, being able to allocate the material within a provided design space, is a mathematical method that can support the design of lightweight components, preserving, at the same time, their mechanical performances. In this paper, a standard shape of a component, specifically an automotive bracket, was topology optimized by estimating the impacts of the new designs from an eco-friendly point of view. A subtractive, an additive and a casting manufacturing process were considered as possible manufacturing routes achieving an optimized geometry of the component for each of them. The topology optimizations were performed considering each processes’ peculiarities, introduced as constraints. Same strength for a given set of loads and boundary conditions was the target of each analysis. The component’s lightening can be considered environmentally friendly just after assessing the impacts associated with all the stages of the product’ life cycle. Indeed, each phase of the product’ life cycle can be affected, differently, by the performed topology optimization taking into account the peculiarities of the employed manufacturing process. The overall considerations on the most environmentally safe strategies can, therefore, change according to the specificities of the optimized shapes. The topology optimization showed its utmost potentiality, from a sustainable point of view, if applied to additive manufacturing techniques for the advantages arisen by the capability to manufacture complex shapes benefiting also of reduction time process owing to less material to be deposited.

Thermal Stress Formation in a Functionally Graded Al2O3-Adhesive Single Lap Joint Subjected to a Uniform Temperature Field

This study investigates the strain and stress states in an aluminum single lap joint bonded with a functionally graded Al2O3 micro particle reinforced adhesive layer subjected to a uniform temperature field. Navier equations of elasticity theory were designated by considering the spatial derivatives of Lamé constants and the coefficient of thermal expansion for local material composition. The set of partial differential equations and mechanical boundary conditions for a two-dimensional model was reduced to a set of linear equations by means of the central finite difference approximation at each grid point of a discretized joint. The through-thickness Al2O3-adhesive composition was tailored by the functional grading concept, and the mechanical and thermal properties of local adhesive composition were predicted by Mori–Tanaka’s homogenization approach. The adherend–adhesive interfaces exhibited sharp discontinuous thermal stresses, whereas the discontinuous nature of thermal strains along bi-material interfaces can be moderated by the gradient power index, which controls the through-thickness variation of particle amount in the local adhesive composition. The free edges of the adhesive layer were also critical due to the occurrence of high normal and shear strains and stresses. The gradient power index can influence the distribution and levels of strain and stress components only for a sufficiently high volume fraction of particles. The grading direction of particles in the adhesive layer was not influential because the temperature field is uniform; namely, it can only upturn the low and high strain and stress regions so that the neat adhesive–adherend interface and the particle-rich adhesive–adherend interface can be relocated.

A black hole toy model with non-local and boundary modes from non-trivial boundary conditions

We study gauge theories between two parallel boundaries with non-trivial boundary conditions, which serve as a toy model for black hole background with two boundaries near the horizon and infinite, aiming for a better understanding of the Bekenstein–Hawking entropy. The new set of boundary conditions allows boundary modes and non-local modes that interplay between the two boundaries. Those boundary modes and Wilson lines stretched between the two boundaries are carefully analyzed and are confirmed as physical variables in the phase space. Along with bulk fluctuation modes and topological modes, the partition function and entropy of all physical modes are evaluated via Euclidean path integral. It is shown that there are transitions between the dominance of different modes as we vary the temperature. The boundary fluctuation modes whose entropy is proportional to the volume dominate at high temperatures, and the boundary-area scaled boundary modes and Wilson lines are the more important at low temperatures. At super-low temperatures, when all the fluctuation modes die off, we see the topological modes whose entropy is the logarithm of the length scales of the system. The boundary modes and non-local modes should have their counterparts in a black hole system with similar boundary conditions, which might provide important hints for black hole physics.

Numerical Simulation of Deformation in Hot Runner Manifold.

This study simulated the deformation of a hot runner manifold and nozzle assembly during operation, aiming to address potential leaks and premature failure. Both thermal and mechanical models were used simultaneously to accurately capture system behavior. A simplified set of boundary conditions was proposed for efficient problem-solving. Analysis of the simulation results revealed that thermal deformation posed a risk of catastrophic failures and leaks. Deformation from melt pressure was relatively small compared to thermal loading, not exceeding 12%. The study provided design recommendations based on the simulation findings, guiding the development of hot runner systems for improved reliability.

On Isospectral Composite Beams

We consider a composite system consisting of two identical straight elastic beams under longitudinal vibration connected by an elastic interface capable of counteracting the relative vibration of the two beams with its shearing stiffness. We construct examples of isospectral composite beams, i.e., countable one-parameter families of beams having different shearing stiffness but exactly the same eigenvalues under a given set of boundary conditions. The construction is explicit and is based on the reduction to a one-dimensional Sturm–Liouville eigenvalue problem and the application of a Darboux’s lemma.

Effects of Last Glacial Maximum (LGM) sea surface temperature and sea ice extent on the isotope–temperature slope at polar ice core sites

Abstract. Stable water isotopes in polar ice cores are widely used to reconstruct past temperature variations over several orbital climatic cycles. One way to calibrate the isotope–temperature relationship is to apply the present-day spatial relationship as a surrogate for the temporal one. However, this method leads to large uncertainties because several factors like the sea surface conditions or the origin and transport of water vapor influence the isotope–temperature temporal slope. In this study, we investigate how the sea surface temperature (SST), the sea ice extent, and the strength of the Atlantic Meridional Overturning Circulation (AMOC) affect these temporal slopes in Greenland and Antarctica for Last Glacial Maximum (LGM, ∼ 21 000 years ago) to preindustrial climate change. For that, we use the isotope-enabled atmosphere climate model ECHAM6-wiso, forced with a set of sea surface boundary condition datasets based on reconstructions (e.g., GLOMAP) or MIROC 4m simulation outputs. We found that the isotope–temperature temporal slopes in East Antarctic coastal areas are mainly controlled by the sea ice extent, while the sea surface temperature cooling affects the temporal slope values inland more. On the other hand, ECHAM6-wiso simulates the impact of sea ice extent on the EPICA Dome C (EDC) and Vostok sites through the contribution of water vapor from lower latitudes. Effects of sea surface boundary condition changes on modeled isotope–temperature temporal slopes are variable in West Antarctica. This is partly due to the transport of water vapor from the Southern Ocean to this area that can dampen the influence of local temperature on the changes in the isotopic composition of precipitation and snow. In the Greenland area, the isotope–temperature temporal slopes are influenced by the sea surface temperatures near the coasts of the continent. The greater the LGM cooling off the coast of southeastern Greenland, the greater the transport of water vapor from the North Atlantic, and the larger the temporal slopes. The presence or absence of sea ice very near the coast has a large influence in Baffin Bay and the Greenland Sea and influences the slopes at some inland ice core stations. The extent of the sea ice far south slightly influences the temporal slopes in Greenland through the transport of more depleted water vapor from lower latitudes to this area. The seasonal variations of sea ice distribution, especially its retreat in summer, influence the isotopic composition of the water vapor in this region and the modeled isotope–temperature temporal slopes in the eastern part of Greenland. A stronger LGM AMOC decreases LGM-to-preindustrial isotopic anomalies in precipitation in Greenland, degrading the isotopic model–data agreement. The AMOC strength modifies the temporal slopes over inner Greenland slightly and by a little on the coasts along the Greenland Sea where the changes in surface temperature and sea ice distribution due to the AMOC strength mainly occur.

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

Abstract. The dissolved organic carbon (DOC) reservoir plays a critical role in the C cycle of marine and freshwater environments because of its size and implication in many biogeochemical reactions. Although it is poorly constrained, its importance in ancient Earth's C cycles is also commonly invoked. Yet DOC is rarely quantified and characterized in modern stratified analogues. In this study, we investigated the DOC reservoirs of four redox-stratified alkaline crater lakes in Mexico. We analyzed the concentrations and isotopic compositions of DOC throughout the four water columns and compared them with existing data on dissolved inorganic and particulate organic C reservoirs (DIC and POC). The four lakes have high DOC concentrations with great variability between and within the lakes (averaging 2 ± 4 mM; 1 SD, n=28; i.e., from ∼ 15 to 160 times the amount of POC). The δ13CDOC signatures also span a broad range of values from −29.3 ‰ to −8.7 ‰ (with as much as 12.5 ‰ variation within a single lake). The prominent DOC peaks (up to 21 mM), together with their associated isotopic variability, are interpreted as reflecting oxygenic and/or anoxygenic primary productivity through the release of excess fixed carbon in three of the lakes (Alberca de los Espinos, La Preciosa, and Atexcac). By contrast, the variability of [DOC] and δ13CDOC in the case of Lake Alchichica is mainly explained by the partial degradation of organic matter and the accumulation of DOC in anoxic waters. The DOC records detailed metabolic functions such as active DIC-uptake and DIC-concentrating mechanisms, which cannot be inferred from DIC and POC analyses alone but which are critical to the understanding of carbon fluxes from the environment to the biomass. Extrapolating our results to the geological record, we suggest that anaerobic oxidation of DOC may have caused the very negative C isotope excursions in the Neoproterozoic. It is, however, unlikely that a large oceanic DOC reservoir could overweigh the entire oceanic DIC reservoir. This study demonstrates how the analysis of DOC in modern systems deepens our understanding of the C cycle in stratified environments and helps to set boundary conditions for the Earth's past oceans.

Influence analysis of working state control angle on electric spring with switchable smart load

AbstractTraditional electric springs can only stabilize the voltage of critical loads (CL), while sacrificing the operational stability of non‐critical loads (NCL), the status of these two loads is obviously unequal, exposure to fluctuating voltages for extended periods of time can be hazardous to NCL. To solve this problem, a control method based on electric spring (ES) with switchable smart load (SSL) that does not distinguish between CL and NCL is proposed. This paper briefly introduces first the definition, principle and control strategy of the ES with SSL. Then, the relationship between the working state control angle in this control strategy and the working state of ES is analysed in detail. A method to obtain reasonable value ranges of working state control angle by setting boundary conditions is studied. Finally, an experimental platform is built based on DSP TMS320F28069 for experiments, experimental results show that ES can stabilize the voltage of different loads in different time by adopting this control strategy, the working state of ES can be adjusted and the four‐quadrant operation of electric spring can be realized by changing the working state control angle.

Smart heat tariffs in transition to free market

Innovative pricing mechanisms should motivate heat suppliers and consumers to move toward more sustainable energy systems and introduce low-temperature district heating systems and sector coupling in smart energy systems. Therefore, district heating regulation regimes should also be changed to stimulate transformations in the energy sector. The district heating tariffs depend on many factors, including fuel prices, operational parameters, taxes, investments, and other criteria. Therefore, an analysis of the DH tariffs has been implemented to find solutions to motivate DH enterprises towards energy efficiency and climate neutrality. The analysis results are based on the decision-making assessment approach by selecting various criteria and evaluating them from five significant aspects: engineering, environmental, climate, economic and socioeconomic. The central elements within the developed fuzzy cognitive mapping model are investment costs, heat production costs, and primary energy consumption. Considering the set boundary conditions, the most beneficial method for smart heat tariff definition could be heat tariff benchmarking with integrated energy efficiency standards for DH operators.

Abnormal flow pattern of low wall shear stress and high oscillatory shear index in spontaneous vertebral artery dissection with vertebral artery hypoplasia.

Spontaneous vertebral artery dissection (sVAD) might tend to develop in vertebral artery hypoplasia (VAH) with hemodynamic dysfunction and it is crucial to assess hemodynamics in sVAD with VAH to investigate this hypothesis. This retrospective study aimed to quantify hemodynamic parameters in patients with sVAD with VAH. Patients who had suffered ischemic stroke due to an sVAD of VAH were enrolled in this retrospective study. The geometries of 14 patients (28 vessels) were reconstructed using Mimics and Geomagic Studio software from CT angiography (CTA). ANSYS ICEM and ANSYS FLUENT were utilized for mesh generation, set boundary conditions, solve governing equations, and perform numerical simulations. Slices were obtained at the upstream area, dissection or midstream area and downstream area of each VA. The blood flow patterns were visualized through instantaneous streamline and pressure at peak systole and late diastole. The hemodynamic parameters included pressure, velocity, time-averaged blood flow, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), endothelial cell action potential (ECAP), relative residence time (RRT) and time-averaged nitric oxide production rate (TARNO). Significant focal increased velocity was present in the dissection area of steno-occlusive sVAD with VAH compared to other nondissected areas (0.910 m/s vs. 0.449 vs. 0.566, p < 0.001), while focal slow flow velocity was observed in the dissection area of aneurysmal dilatative sVAD with VAH according to velocity streamlines. Steno-occlusive sVAD with VAH arteries had a lower time-averaged blood flow (0.499 cm3/s vs. 2.268, p < 0.001), lower TAWSS (1.115 Pa vs. 2.437, p = 0.001), higher OSI (0.248 vs. 0.173, p = 0.006), higher ECAP (0.328 Pa-1 vs. 0.094, p = 0.002), higher RRT (3.519 Pa-1 vs. 1.044, p = 0.001) and deceased TARNO (104.014 nM/s vs. 158.195, p < 0.001) than the contralateral VAs. Steno-occlusive sVAD with VAH patients had abnormal blood flow patterns of focal increased velocity, low time-averaged blood flow, low TAWSS, high OSI, high ECAP, high RRT and decreased TARNO. These results provide a good basis for further investigation of sVAD hemodynamics and support the applicability of the CFD method in testing the hemodynamic hypothesis of sVAD. More detailed hemodynamic conditions with different stages of sVAD are warranted in the future.

On Recovering Sturm–Liouville-Type Operators with Global Delay on Graphs from Two Spectra

We suggest a new formulation of the inverse spectral problem for second-order functional-differential operators on star-shaped graphs with global delay. The latter means that the delay, which is measured in the direction of a specific boundary vertex, called the root, propagates through the internal vertex to other edges. Now, we intend to recover the potentials from the spectra of two boundary value problems on the graph with a common set of boundary conditions at all boundary vertices except the root. For simplicity, we focus on star graphs with equal edges when the delay parameter is not less than their length. Under the assumption that the common boundary conditions are of the Robin type and they are known and pairwise linearly independent, the uniqueness theorem is proven and a constructive procedure for solving the proposed inverse problem is obtained.

Static behavior of elastically supported transversely inhomogeneous porous functionally graded plate with different thickness variations under a variety of external loadings

The static behavior of a porous functionally graded material plate (FGMP) with variable thickness placed on two parametric elastic foundations exposed to various boundary conditions is investigated in this study. Thickness variation in the plate is assumed to vary in uni-direction/bi-direction with linear and parabolic variations. The properties of the constituent of FGMs are expected to change in the direction of thickness following the power law. The plate is subjected to three types of external loadings: uniformly distributed load (UDL), linearly increasing load (LIL), and linearly increasing decreasing load (LIDL). To explore the static behavior, numerical parameters (NP) linked with the bending and normal stresses of the plate have been determined. Classical plate theory is used to derive the governing equation using the energy principle. The transverse displacement functions are indigenously developed in the form of simple algebraic polynomials (using Pascal’s triangle) to handle any set of mixed- boundary conditions. The Rayleigh–Ritz method along with the algebraic polynomial is employed in the numerical simulation for getting NP. This method is straightforward, precise, and computationally efficient as it can handle any set of boundary conditions and the solution converges with very few iterations. Following the convergence and validation analyses, new findings are presented. The influence of aspect ratios, power-law exponents, porosity volume fraction, taper ratios, and the Winkler and Pasternak modulus on the NP of the plate has been thoroughly examined. The effect of various types of external loading and boundary conditions on deformed shapes and co-ordinate of maximum deflection of elastically supported porous FGMP with different thickness variations have also been reported. One of the important findings is that the effect of homogeneous porosity distribution on NP is more pronounced than in situations with non-homogeneous distributions. Also, the change in thickness of the plate and the distribution of various types of porosity has a substantial effect on the deformed shape of the plate. One of the interesting observations of this study is that the deformation in the plate is more significant in the case of bi-linear thickness variation compared to the uni-linear case. The results reported in this article are accurate enough to consider for further research and experimentation.

Investigating the Effects of Polynomial Trajectories on Energy Consumption of Quadrotors

This article focuses on investigating the effect of quadrotor's trajectory, especially polynomial trajectories, on its energy consumption. First, model-free expressions for power and energy quotients are introduced to relate quadrotor's power and energy directly to its acceleration. This allows to qualitatively estimate quadrotor's energy consumption and compare the effect of different trajectories on energy consumption of identical or different quadrotors independent of quadrotor's manufacturing specifications. Then, polynomial trajectories are analytically investigated for rest-to-rest 1-D scenarios. Scenarios in 3-D with arbitrary kinematic boundary conditions are analyzed via Monte Carlo Simulations with a sample of 10 000 sets of arbitrary boundary conditions. Polynomial trajectories are compared to energy-minimized trajectories in the literature. The results show that increasing the degree of the polynomial increases quadrotor's energy consumption. Moreover, this article suggests using minimum acceleration trajectories as energy-efficient polynomial trajectories. Finally, the results are validated experimentally.

High-efficiency and cost-effective manufacturing of solar cells based on localized surface plasmonic resonance

Improving photovoltaic efficiency is essential to the early realization of universal solar cell application, which has proven to be the most promising solution to the global energy transition. Therefore, we propose a thin-film GaAs solar cell with TiO2 quantum dots, plasmonic Ag nanoparticles, and the AlGaAs window layer. First, we using the finite difference time domain method to simulate the electromagnetic wave propagation and the solar cell light absorption under set boundary conditions to test whether the TiO2 quantum dots and plasmonic Ag nanoparticles can improve the cell light-trapping ability. The results show that the light absorption of the cell can be maintained above 95% in the visible wavelength range of 300–721 nm, with an average absorption of 97.7%. The photoabsorption effect is particularly prominent at 558 nm, with an absorption rate of 99.86%. The p-n junction doping concentration and the molar fraction of the AlGaAs window layer were optimized to obtain better photovoltaic performance parameters. The results show that AlGaAs reduces incident light loss and possesses a higher potential barrier in the emitter region because of its wider band gap, effectively lowering carrier recombination rate and consequently enhancing the photovoltaics characteristics of the cell. The short-circuit current density, open-circuit voltage, and photoelectric conversion efficiency (PCE) of the thin-film GaAs solar cell improved to 30.01 mA/cm2, 1.247 V, and 33.43%, respectively. Thus, this study provides an effective strategy for high-performance fabrication of the thin-film solar cells, demonstrating significant potential for broad applications in cost-effective solar cell usage and mitigating the climate change crisis.

Frequency varying rheology-based fluid–structure-interactions waves in liquid-filled visco-elastic pipes

This contribution proposes a new rheology-based model for water-hammer wave propagation in visco-elastic pipes. Using a long wavelength analysis and a generalized frequency-dependent Hooke-law for the stress/strain relation, the pressure/longitudinal stress coupled wave system is derived. In this general framework, a visco-elastic Fluid–Structure Interaction (FSI) four equations model is derived by having four visco-elastic kernels associated with the non-local time response of the visco-elastic solid. The explicit dependence of these kernels with the material creep function and the pipe dimension is found. Considering a general linear visco-elastic rheology, the four visco-elastic kernels, and the corresponding creep function are explicitly derived in frequency and time-domain versus four visco-elastic parameters. For a given set of boundary conditions, a general analytical solution for the pressure/stress water hammer wave is obtained in frequency domain. The model’s predictions are successfully compared with experimental measurements as well as with other models adjusted to the same experimental data set by calibrating the model’s parameter. The proposed model can be used in many other contexts with the specific ability to distinguish the intrinsic visco-elastic rheology from the considered pipe geometry and boundary conditions.