Search Results (60)

Control of buoyancy-assisted convective flow and the associated thermal behavior of nanofluids in finite-sized conduits has become a great challenge for the design of many types of thermal equipment, particularly for heat exchangers. This investigation discusses the numerical simulation of the buoyancy-driven convection (BDC) of a nanofluid (NF) in a differently heated cylindrical annular domain with an interior cylinder attached with a thin baffle. The annular region is filled with non-Darcy porous material saturated-nanofluid and both NF and the porous structure are in local thermal equilibrium (LTE). Higher thermal conditions are imposed along the interior cylinder as well as the baffle, while the exterior cylinder is maintained with lower or cold thermal conditions. The Darcy–Brinkman–Forchheimer model, which accounts for inertial, viscous, and non-linear drag forces was adopted to model the momentum equations. An implicit finite difference methodology by considering time-splitting methods for transient equations and relaxation-based techniques is chosen for the steady-state model equations. The impacts of various pertinent parameters, such as the Rayleigh and Darcy numbers, baffle dimensions, like length and position, on flow, thermal distributions, as well as thermal dissipation rates are systematically estimated through accurate numerical predictions. It was found that the baffle dimensions are very crucial parameters to effectively control the flow and associated thermal dissipation rates in the domain. In addition, machine learning techniques were adopted for the chosen analysis and an appropriate model developed to predict the outcome accurately among the different models considered. Full article

Diffusiophoresis of a weakly charged dielectric droplet in a cylindrical pore is investigated theoretically in this study. The governing fundamental electrokinetic equations are solved with a patched pseudo-spectral method based on Chebyshev polynomials, coupled with a geometric mapping scheme to take care of the irregular solution domain. The impact of the boundary confinement effect upon the droplet motion is explored in detail, which is most profound in narrow channels. We found, among other things, that the droplet moving direction may reverse with varying channel widths. Enhanced motion-inducing double-layer polarization due to the presence of a nearby channel wall is found to be responsible for it. In particular, an interesting and seemingly peculiar phenomenon referred to as the “solidification phenomenon” is observed here at some specific critical droplet sizes or electrolyte strengths in narrow channels, under which all the droplets move at identical speeds regardless of their viscosities. They move like a rigid particle without the surface spinning motions and the induced interior recirculating vortex flows. As the corresponding shear rate is zero at this point, the droplet is resilient to undesirable exterior shear stresses tending to damage the droplet in motion. This provides a helpful guideline in the fabrication of liposomes in drug delivery in terms of the optimal liposome size, as well as in the microfluidic and nanofluidic manipulations of cells, among other potential practical applications. The effects of other parameters of electrokinetic interest are also examined. Full article

This manuscript addresses an application study by employing a mathematical model of a thermoelastic plate weakened by multi-curved holes under the effect of stress forces in the presence of heat conduction. When the initial heat flow is directed to the plate system, complex variable procedures are used to compute the basic Goursat functions, taking into account the time-dependent variables through conformal mapping, which transfers the domain to the exterior of a unit circle. The problem reduces to a general form of a contact problem in two dimensions, which is called an integrodifferential equation of the second type with the Cauchy kernel. Additionally, different hole shapes are generated using Maple 2023. Computational simulations are performed to determine the normal and shear stress components in the presence and absence of heat effects at various times. Furthermore, numerical calculations of Goursat functions are carried out and graphically displayed for some specific materials. This investigation provides valuable information about industries, such as those regarding ceramic tile, glass, rubber, paint, ceramic pigment, and metal alloys. Full article

Traditional Japanese architecture is known for its open, ambiguous spatial boundaries (“kyokai”), which integrate nature and dwelling through Zen/Shinto philosophies. Yet modern urban housing, driven by high-density minimalism, flattens spatial hierarchies and erodes these rich boundary concepts. This study aims to explore how Japanese architect Yoshiji Takehara reinterprets traditional spatial principles to reconstruct the interior–exterior relationships in modern housing through a mixed-methods approach—including a literature review, case studies, and semi-structured interviews—verifying the hypothesis that he achieves the modern translation of traditional “kyokai” through strategies of boundary expansion and ambiguity. Analyzing 78 independent residential projects by Takehara and incorporating his interview texts, the research employs spatial typology and statistical methods to quantify the characteristics of boundary configurations, such as building contour morphology, opening orientations, and transitional space types, to reveal the internal logic of his design strategies. This study identifies two core strategies through which Takehara redefines spatial boundaries: firstly, clustered building layouts, multi-directional openings, and visual connections between courtyards and private functional spaces extend interface areas, enhancing interactions between nature and daily life; secondly, in-between spaces like corridors and doma (earthen-floored transitional zones), double-layered fixtures, and floor-level variations blur physical and psychological boundaries, creating multilayered permeability. Case studies demonstrate that his designs not only inherit traditional elements such as indented plans and semi-outdoor buffers but also revitalize the essence of “dwelling” through contemporary expressions, achieving dynamic visual experiences and poetic inhabitation within limited sites via complex boundary configurations and fluid thresholds. This research provides reusable boundary design strategies for high-density urban housing, such as multi-directional openings and buffer space typologies, and fills a research gap in the systematic translation of traditional “kyokai” theory into modern architecture, offering new insights for reconstructing the natural connection in residential spaces. Full article

Background: The majority of antigen-based SARS-CoV-2 (SCV2) vaccines utilized in the clinic have had the Spike protein or domains thereof as the immunogen. While the Spike protein is highly immunogenic, it is also subject to genetic drift over time, which has led to a series of variants of concern that continue to evolve, requiring yearly updates to the vaccine formulations. In this study, we investigate the potential of the N-terminal ectodomain of the ORF3a protein encoded by the orf3a gene of SCV2 to be an evolution-resistant vaccine antigen. This domain is highly conserved over time, and, unlike many other SCV2 conserved proteins, it is present on the exterior of the virion, making it accessible to antibodies. ORF3a is also important for eliciting robust anti-SARS-CoV-2 T-cell responses. Methods: We designed a DNA vaccine by fusing the N-terminal ectodomain of orf3a to macrophage-inflammatory protein 3α (MIP3α), which is a chemokine utilized in our laboratory that enhances vaccine immunogenicity by targeting an antigen to its receptor CCR6 present on immature dendritic cells. The DNA vaccine was tested in mouse immunogenicity studies, vaccinating by intramuscular (IM) electroporation and by intranasal (IN) with CpG adjuvant administrations. We also tested a peptide vaccine fusing amino acids 15–28 of the ectodomain to immunogenic carrier protein KLH, adjuvanted with Addavax. Results: The DNA IM route was able to induce 3a-specific splenic T-cell responses, showing proof of principle that the region can be immunogenic. The DNA IN route further showed that we could induce ORF3a-specific T-cell responses in the lung, which are critical for potential disease mitigation. The peptide vaccine elicited a robust anti-ORF3a antibody response systemically, as well as in the mucosa of the lungs and sinus cavity. Conclusions: These studies collectively show that this evolutionarily stable region can be targeted by vaccination strategies, and future work will test if these vaccines, alone or in combination, can result in reduced disease burden in animal challenge models. Full article

In this paper, we present mathematical geometric models and recursive algorithms to generate and design complex patterns using fractal structures. By applying analytical, iterative methods, iterative function systems (IFS), and L-systems to create geometric models of complicated fractals, we developed fractal construction models, visualization tools, and fractal measurement approaches. We introduced a novel recursive fractal modeling (RFM) method designed to generate intricate fractal patterns with enhanced control over symmetry, scaling, and self-similarity. The RFM method builds upon traditional fractal generation techniques but introduces adaptive recursion and symmetry-preserving transformations to produce fractals with applications in domains such as medical imaging, textile design, and digital art. Our approach differs from existing methods like Barnsley’s IFS and Jacquin’s fractal coding by offering faster convergence, higher precision, and increased flexibility in pattern customization. We used the RFM method to create a mathematical model of fractal objects that allowed for the viewing of polygonal, Koch curves, Cayley trees, Serpin curves, Cantor set, star shapes, circulars, intersecting circles, and tree-shaped fractals. Using the proposed models, the fractal dimensions of these shapes were found, which made it possible to create complex fractal patterns using a wide variety of complicated geometric shapes. Moreover, we created a software tool that automates the visualization of fractal structures. This tool may be used for a variety of applications, including the ornamentation of building items, interior and exterior design, and pattern construction in the textile industry. Full article

This paper concerns the viscous Boussinesq equations without a dissipation term and their relation to the temperature equation related to the exterior of a ball with a smooth boundary. We first prove the global existence of weak solutions on the bounded domain $\tilde{\Omega }$ via the Schauder fixed-point theorem. Then, we derive the uniform estimates to obtain the global existence of weak solutions on the unbounded domain $\Omega$ by utilizing the domain expansion method. Finally, we show that the equations have a unique classical solution for $H^3$ initial data by a series of regularity estimations. Full article

The discrete null-field equation method (DNFEM) was proposed based on the null-field equation (NFE) of Green’s representation formulation, where only disk domains were discussed. However, the study of the DNFEM for bounded simply connected domains S is essential for practical applications. Since the source nodes must be located outside of a solution domain S, the first issue in computations is how to locate them. It includes two topics—Topic I: The source nodes must be located not only outside S but also outside the exterior boundary layers. The width of the exterior boundary layers is derived as $O(1/N)$, where N is the number of unknowns in the DNFEM. Topic II: There are numerous locations for source nodes outside the exterior boundary layers. Based on the sensitivity index, several better choices of pseudo-boundaries are studied for bounded simply connected domains. The advanced study of Topics I and II needs stability and error analysis. The bounds of condition numbers (Cond) are derived for bounded simply connected domains, and they are similar to those of the method of fundamental solutions (MFS). New error bounds are also provided for bounded simply connected domains. The thorough study of determining better locations of source nodes is also valid for the MFS and the discrete boundary integral equation method (DBIEM). The development of algorithms based on the NFE lags far behind that of the traditional boundary element method (BEM). Some progress has been made by following the MFS, and reported in this paper. From the theory and computations in this paper, the DNFEM may become a competent boundary method in scientific/engineering computing. Full article

The presence of water accumulation on aircraft surfaces constitutes a considerable hazard to both performance and safety, necessitating vigilant inspection and maintenance protocols. In this study, we introduce an innovative semantic segmentation model, grounded in deep learning principles, for the precise identification and delineation of water accumulation areas within infrared images of aircraft exteriors. Our proposed model harnesses the robust features of ResNet, serving as the foundational architecture for U-Net, thereby augmenting the model’s capacity for comprehensive feature characterization. The incorporation of channel attention mechanisms, spatial attention mechanisms, and depthwise separable convolution further refines the network structure, contributing to enhanced segmentation performance. Through rigorous experimentation, our model surpasses existing benchmarks, yielding a commendable 22.44% reduction in computational effort and a substantial 38.89% reduction in parameter count. The model’s outstanding performance is particularly noteworthy, registering a 92.67% mean intersection over union and a 97.97% mean pixel accuracy. The hallmark of our innovation lies in the model’s efficacy in the precise detection and segmentation of water accumulation areas on aircraft skin. Beyond this, our approach holds promise for addressing analogous challenges in aviation and related domains. The enumeration of specific quantitative outcomes underscores the superior efficacy of our model, rendering it a compelling solution for precise detection and segmentation tasks. The demonstrated reductions in computational effort and parameter count underscore the model’s efficiency, fortifying its relevance in broader contexts. Full article

Low-density polyethylene (LDPE) is among the most abundant synthetic plastics in the world, contributing significantly to the plastic waste accumulation problem. A variety of microorganisms, such as Cupriavidus necator H16, Pseudomonas putida LS46, and Pseudomonas chlororaphis PA2361, can form biofilms on the surface of LDPE polymers and cause damage to the exterior structure. However, the damage is not extensive and complete degradation has not been achieved. The changes in polymer structure were analyzed using Time-domain Nuclear Magnetic Resonance (TD-NMR), High-Temperature Size-Exclusion Chromatography (HT-SEC), Differential Scanning Calorimetry (DSC), and Gas Chromatography with a Flame Ionization Detector (GC-FID). Limited degradation of the LDPE powder was seen in the first 30 days of incubation with the bacteria. Degradation can be seen in the LDPE weight loss percentage, LDPE degradation products in the supernatant, and the decrease in the percentage of amorphous regions (from >47% to 40%). The changes in weight-average molar mass (Mw), number-average molar mass (Mn), and the dispersity ratio (Đ) indicate that the low-molar mass fractions of the LDPE were preferentially degraded. The results here confirmed that LDPE degradation is heavily dependent on the presence of amorphous content and that only the amorphous content was degraded via bacterial enzymatic action. Full article

The motion of viscous incompressible magnetohydrodynamics (MHD) is considered in a domain that is bounded by a free surface. The motion interacts through the free surface with an electromagnetic field located in a domain exterior to the free surface and bounded by a given fixed surface. Some electromagnetic fields are prescribed on this fixed boundary. On the free surface, jumps in the magnetic and electric fields are assumed. The global existence of solutions to this problem assuming appropriate smallness conditions on the initial and boundary data is proved. Full article

In the domain of supervised learning, interpolation and extrapolation serve as crucial methodologies for predicting data points within and beyond the confines of a given dataset, respectively. The efficacy of these methods is closely linked to the nature of the dataset, with increased challenges when multivariate feature vectors are handled. This paper introduces a novel prediction framework that integrates interpolation and extrapolation techniques. Central to this method are two main innovations: an optimization model that effectively classifies new multivariate data points as either interior or exterior to the known dataset, and a hybrid prediction system that combines k-nearest neighbor (kNN) and linear regression. Tested on the port state control (PSC) inspection dataset at the port of Hong Kong, our framework generally demonstrates superior precision in predictive outcomes than traditional kNN and linear regression models. This research enriches the literature by illustrating the enhanced capability of combining interpolation and extrapolation techniques in supervised learning. Full article

When solving open-region electromagnetic scattering problems using the standard finite element method, the infinite region exterior to the scatterer must be truncated with an artificial outer boundary. In the interior or finite part of the domain, finite elements can be used, but a boundary condition must be introduced at this artificial boundary to obtain a unique finite element solution. One class of boundary conditions designed for this purpose is called absorbing boundary conditions (ABCs). Several ABCs have been reported in the literature. These can be broadly classified into two categories: local and non-local. In this paper, we present new closed-form expressions for Nth-order local ABCs, equivalent to the well-known sequences of the Bayliss, Gunzburger, and Turkel boundary operators. To the best of our knowledge, these expressions have not yet been reported in the literature. Two- and three-dimensional problems are considered in this study. We also discuss the problem of incorporating custom ABCs into commercial finite element method programs, which are usually closed-source software packages. Two 2D electromagnetic scattering and radiation problems with known analytical solutions are analyzed. Full article

The successful operation of a large-diameter cold water pipeline installation is crucial for harnessing the potential of ocean thermal energy conversion. However, there is a shortage of research focused on mechanical performance analysis during installation. This study establishes a pipeline response analysis model based on a nonlinear beam theory to elucidate the underlying mechanical behaviour. Employing the method of singular perturbation, the general solution for the exterior region of the pipeline, the solution at the boundary layer, and the valid solution across the entire domain are derived. A comparison with numerical solutions is conducted to validate the accuracy and effectiveness of the theoretical model. Based on the theoretical analysis, the influence of installation depth and pipeline curvature on the pipeline’s shape, tension, curvature, and stress is discussed. The results indicate that increasing the installation depth leads to intensified pipeline bending and significant deformation, reaching a maximum bending moment of 3.92 MN∙m at a distance of 50~100 m from the bottom of the pipeline. The results also show that, as the pipeline’s arc length increases from 0 to 100 m, the bending curvature, Von Mises stress, and bending stress exhibit a trend of initial growth followed by a decline, peaking at 7.45 MPa, and 6.83 Mpa, respectively, while the actual tension and axial tension decrease initially and then increase, reaching −0.17 MN and −0.17 MPa, respectively, at the maximum arc length. The findings of this study provide valuable insights for practical cold-water pipe installation and laying. Full article