Homogeneous Parameters Research Articles

Revealing the time-dependent electromechanically coupled performances of viscoelastic MWCNT/polyethylene nanocomposite stress sensors

While highly sensitive elastic strain sensors have been widely investigated, the time-dependent stress sensitivity of viscoelastic MWCNT/polyethylene nanocomposite stress sensors remains to be explored. In this paper, we develop an electromechanically coupled homogenization scheme to reveal the time-dependent stress sensing performances of viscoelastic MWCNT/polyethylene nanocomposite sensors. In the time-dependent context, the complex moduli and electrical conductivity are selected as the dual homogenization parameters. The time-dependent stress sensitivity is illustrated through the viscoelastic imperfect interface connection and stress-induced tunneling distance. The predicted stress sensing capacities of viscoelastic MWCNT/polyethylene nanocomposite stress sensors are shown to be consistent with the experiments under the constant stress loading. It reveals that the stress sensitivity factor increases with the loading time under constant stress. The optimal MWCNT aspect ratio for high sensing capacities exhibits an increasing trend regarding the MWCNT volume fraction. The uncovered sensing characteristics can provide microstructural design guidance in high-performance nanocomposite stress sensors.

Primary study of the relative and compound biological effectiveness model for boron neutron capture therapy based on nanodosimetry.

The current radiobiological model employed for boron neutron capture therapy (BNCT) treatment planning, which relies on microdosimetry, fails to provide an accurate representation the biological effects of BNCT. The precision in calculating the relative biological effectiveness (RBE) and compound biological effectiveness (CBE) plays a pivotal role in determining the therapeutic efficacy of BNCT. Therefore, this study focuses on how to improve the accuracy of the biological effects of BNCT. The purpose of this study is to propose new radiation biology models based on nanodosimetry to accurately assess RBE and CBE for BNCT. Nanodosimetry, rooted in ionization cluster size distributions (ICSD), introduces a novel approach to characterize radiation quality by effectively delineating RBE through the ion track structure at the nanoscale. In the context of prior research, this study presents a computational model for the nanoscale assessment of RBE and CBE. We establish a simplified model of DNA chromatin fiber using the Monte Carlo code TOPAS-nBio to evaluate the applicability of ICSD to BNCT and compute nanodosimetric parameters. Our investigation reveals that both homogeneous and heterogeneous nanodosimetric parameters, as well as the corresponding biological model coefficients α and β, along with RBE values, exhibit variations in response to varying intracellular 10B concentrations. Notably, the nanodosimetric parameter effectively captures the fluctuations in model coefficients α and RBE. Our model facilitates a nanoscale analysis of BNCT, enabling predictions of nanodosimetric quantities for secondary ions as well as RBE, CBE, and other essential biological metrics related to the distribution of boron. This contribution significantly enhances the precision of RBE calculations and holds substantial promise for future applications in treatment planning.

Numerical Investigation of Three-Dimensional Magnetohydrodynamic Flow of Ag 􀀀 H2O Nanofluid Over an Oscillating Surface in a Rotating Porous Medium

Objective: To investigate the three-dimensional flow of a nanofluid (Ag-water) over a stretchable vertical oscillatory sheet. This study involves considering fluctuating temperatures on the sheet and comparing them to the free stream temperature. The formulation of the unsteady boundary layer equations leading to the flow of nanofluid also takes into consideration the occurrence of the heterogeneous-homogeneous chemical reaction and thermal radiation. Method: The governing equations and the boundary conditions have been derived in a dimensionless form by using the appropriate transformations, and they are then solved using an EFDS (Explicit Finite Difference Scheme) in Matlab software. The Von-Neumann stability analysis is used to determine the method’s stability requirements for constant sizes of the grid. Findings: The physical factors impact on the concentration fields, temperature distribution, and velocity distribution were obtained and are studied by graphs and described in extensive detail. Convergence and stability requirements are attained in order to achieve accurate solutions. Novelty: In this study fluctuations in the temperature and stretching velocity of sheet on three-dimensional magnetohydrodynamic flow of Ag − H2O nanofluid over an oscillating surface through rotating porous are taken into account. Impacts of porous media permeability, velocity slip, magnetic fields, nanoparticle volume fraction, heat radiation, rotation, and homogeneous and heterogeneous chemical reaction parameters had all been attempted to be determined. Keywords: Oscillatory Surface, Heat transmission, Nonlinear PDE, Explicit Finite Difference Scheme, Nanoparticle

Man vs. machine: Automated bioink mixing device improves reliability and reproducibility of bioprinting results compared to human operators

The bioink mixing process is highly relevant to the bioink quality, which is the basis for reproducible extrusion-based three-dimensional (3D) bioprinting (EBB). Currently, most bioinks mixed by skilled human operators show variations in terms of cell homogeneity and biological properties as well as other properties. For preparation of many types of bioinks, striking the balance between homogeneity and cell viability remains a major challenge. This study investigates the relationship between bioink homogeneity and mixing parameters, particularly mixing speed and number of exchanges, utilizing a customized automated device. We found that up to a certain point, increasing the rate of mixing led to a better distribution of cells within the bioink, but beyond that point, there was a detrimental effect on cell viability. In contrast, the mixing number had less impact on the physiological properties of the cells in the bioink. Furthermore, a comparison between skilled human and machine bioink mixing revealed that the machine consistently provided better outcomes in terms of bioink homogeneity, cell distribution, and cell viability, highlighting the advantages and importance of standardizing the bioink mixing process. The methodology and approaches in this study can improve the reproducibility and reliability of EBB bioink and may thereby advance the field of 3D bioprinting in various applications.

Optimizing extreme limited entry design for lateral heterogeneous reservoirs

Extreme limited entry (XLE) method can enhance hydraulic fracture uniformity by elevating wellbore pressure to overcome reservoir heterogeneity. However, it increases surface pressure and decreases hydraulic fracturing efficiency. In this paper, the effects of stress shadow and heterogeneity of the lateral breakdown pressure on fracture propagation are numerically studied, from which an optimization method is proposed for the XLE design with the minimal requirement of fracturing pressure. Initially, the unconventional fracture model is applied to analyze fracture propagation in formations with homogeneous geomechanical parameters and various perforation designs. Fracture length distribution is correlated with perforation friction, revealing insights into the influence of geomechanical parameters and fracture spacing. Then, the uniformity of fracture propagation is assessed for different XLE designs by varying lateral breakdown pressures. Simulation results are utilized to develop a cross-plot of fracture length distributions vs normalized perforation frictions for optimizing an XLE design. In homogeneous reservoirs, decreasing perforation spacing and increasing perforation hole erosion rate slow down the reduction in the fracture length distribution span with perforation friction, necessitating a higher perforation friction for uniform fractures. In all simulated cases, a similar trend is observed when the distribution of fracture lengths is plotted vs the normalized perforation friction to the difference of breakdown pressure within one fracturing stage. It is recommended that this normalized value be maintained above 2 in an XLE design. This new plot makes the conventional horn-shaped plot more applicable to reservoirs with heterogeneous lateral breakdown pressures.

Beyond Gaia DR3: Tracing the [α/M] – [M/H] bimodality from the inner to the outer Milky Way disc with Gaia-RVS and convolutional neural networks

Context. In June 2022, Gaia DR3 provided the astronomy community with about one million spectra from the Radial Velocity Spectrometer (RVS) covering the CaII triplet region. In the next Gaia data releases, we anticipate the number of RVS spectra to successively increase from several 10 million spectra to eventually more than 200 million spectra. Thus, stellar spectra are projected to be produced on an ‘industrial scale’, with numbers well above those for current and anticipated ground-based surveys. However, one-third of the published spectra have 15 ≤ S /N ≤ 25 per pixel such that they pose problems for classical spectral analysis pipelines, and therefore, alternative ways to tap into these large datasets need to be devised. Aims. We aim to leverage the versatility and capabilities of machine learning techniques for supercharged stellar parametrisation by combining Gaia-RVS spectra with the full set of Gaia products and high-resolution, high-quality ground-based spectroscopic reference datasets. Methods. We developed a hybrid convolutional neural network (CNN) that combines the Gaia DR3 RVS spectra, photometry (G, G_BP, G_RP), parallaxes, and XP coefficients to derive atmospheric parameters (Teff, log(g) as well as overall [M/H]) and chemical abundances ([Fe/H] and [α/M]). We trained the CNN with a high-quality training sample based on APOGEE DR17 labels. Results. With this CNN, we derived homogeneous atmospheric parameters and abundances for 886 080 RVS stars that show remarkable precision and accuracy compared to external datasets (such as GALAH and asteroseismology). The CNN is robust against noise in the RVS data, and we derive very precise labels down to S/N =15. We managed to characterise the [α/M] - [M/H] bimodality from the inner regions to the outer parts of the Milky Way, which has never been done using RVS spectra or similar datasets. Conclusions. This work is the first to combine machine learning with such diverse datasets and paves the way for large-scale machine learning analysis of Gaia-RVS spectra from future data releases. Large, high-quality datasets can be optimally combined thanks to the CNN, thereby realising the full power of spectroscopy, astrometry, and photometry.

Heterogeneities of grain boundary contact for simulation of laboratory-scale mechanical behavior of granitic rocks

From a practical point of view, grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative manner. One of the less discussed topics in the context of the grain-based model (GBM) in the particle flow code (PFC) is the contact heterogeneities and the appropriate contact model to mimic the grain boundary behavior. Generally, the smooth joint (SJ) model and linear parallel bond (LPB) model are used to simulate the grain boundary behavior. However, the literature does not document the suitability of different models for specific problems. Another challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain boundaries. The aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models, considering grain boundary heterogeneous and homogeneous contact parameters. Uniaxial and biaxial compression tests are performed to calibrate the response of Creighton granite. The stress–strain curves, volumetric dilation, inter-crack (crack in the grain boundary), and intra-crack (crack within the grain) development, and failure patterns associated with different contact models are examined. It was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock type. However, the LPB model is unable to reproduce the post-peak behavior. Due to the large interlocking effect originating from the balls in contact and the ball size in the LPB model, local dilation is induced at the grain boundaries. This overestimates the volumetric dilation and residual shear strength. The LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen, resulting in fine fragments at the rock surface during failure.

ANALYTICAL AND NUMERICAL ANALYSIS OF SOLID CYLINDER MADE OF RADIALLY NONUNIFORM MATERIAL UNDER EXTENSION

Functionally graded materials are inhomogeneous composite materials, composed of two or more constituents selected to achieve desirable properties for specific applications. In this work, a solid cylindrical tube made of inhomogeneous composite materials under tensile action was analyzed within the context of three-dimensional elasticity theory. An analytical solution was obtained for computing the displacement and stress fields. It has been assumed that the elastic stiffness is varying through the functionally graded material according to radial variation laws: linear, power, and exponential laws, while Poisson's ratio is considered as constant. In order to check the relevance of the analytical solution, a finite element model of the cylindrical tube was constructed, taking into account variations in Young's modulus. Very good agreement has been found between the numerical results and the predictions of the analytical solution, which confirms the accuracy of our model. Numerous curves were plotted by adjusting the inhomogeneity parameter and the elongation value, revealing a significant effect. Thus, the inhomogeneity in material properties can be exploited to optimize stress distribution. Indeed, by tailoring the material properties to match the stress distribution in a specific load scenario, stress concentrations can be minimized in high-stress areas.

Exploring Symmetry-Induced Divergence in Decentralized Electric Vehicle Scheduling

Due to the low computational efficiency and high communication pressure caused by centralized control, decentralized coordination of electric vehicles (EVs) has become a research hotspot in recent years. However, the integration of numerous EVs with homogeneous parameters brings unprecedented challenges for the optimal scheduling of the power system. To explore symmetry-induced divergence in decentralized electric vehicle scheduling, the established centralized optimization scheduling model of electric vehicles is decomposed into a distributed optimization model by Lagrange relaxation, achieving parallel control of each EV aggregator (EVA). To solving the oscillation caused by parameter symmetry in the process of optimization, we propose a convergence acceleration algorithm based on a perturbation function, which is a random distribution function used to break parameter symmetry within an acceptable calculation error range. On the premise of sensitivity analysis, a closed form of the perturbation limit is theoretically derived. Case studies based on different scales of users validate the effectiveness and computational efficiency of the proposed method.

Irreversibility and nanomaterials shape consequences on peristalsis of magneto hybrid nanofluid via curved configuration with homogeneous–heterogeneous chemical reactions

Over the last decade, research on nanofluids has grown at a breakneck pace. As part of their nanofluid research, researchers have recently attempted to use hybrid nanofluids, made by combining different nanomaterials. The novelty of this analysis is to inspect the consequences of entropy generation on the peristalsis of a hybrid nano-liquid via a curved conduit with homogeneous and heterogeneous chemical reactions. Hybrid nanofluid is formed of copper and iron oxide nanomaterials added to water. Furthermore, the simplified model also considered the Hall current, viscous dissipation, and electrical resistance heating effects. The Hamilton–Crosser thermal conductivity model is used to study the nanomaterials shape effects (i.e. sphere, platelet, and blade) on the thermal features of hybrid nano-liquids. Mathematical expressions for the flow problem are simplified by employing the small wave and Reynolds numbers assumptions, which are then resolved analytically and numerically. Analytical results are used to scrutinize the impacts of several included quantities on the flow and thermal characteristics, chemically reactive concentration, and entropy creation. It is found that with a rise in Hartmann number, the velocity reduces, whereas an improvement is noted in temperature and entropy production for large values of Hartmann number. The noteworthy discoveries indicate that hybrid nano-liquids exhibit enhanced thermal efficiency when compared to conventional nanofluids. Specifically, the introduction of a small quantity of ferrous oxide nanoparticles into the copper–water nanofluid led to less than 2% increase in the thermal transport rate. Additionally, it was observed that spherical-shaped nanoparticles generate more heat in comparison to platelets and blade-shaped nanoparticles. Furthermore, the homogenous reaction parameter and Schmidt number lead to a drop in the concentration profile.

A SHORTENED VERSION OF THE ACHIEVEMENT MOTIVE SCALE – MOP-20

This research was focused on reducing the scale measuring the general achievement motive MOP2002. The initial version of the instrument MOP2002 contains 55 items and is in the Likert- type scale format. The starting point of this research was based on the assumption about a four-factor structure of the general achievement motive established in our previous research. Both quantitative and qualitative studies were applied in the process of reduction. Each of these studies was conducted on a separate sample – exploratory factor analysis N = 2846, and confirmatory factor analysis N = 294 – and four focus groups, each including 15 respondents. Based on the obtained results, 20 items were selected, and they comprise a shortened version of the scale called MOP20. Designed in this way, the scale can also take the form of the observation protocol while assessing the general achievement motive. It was ascertained that the instrument had a unique object of measurement. The factor analyses results showed the stability of the four-factor structure of the achievement motive. The parameters of representativeness, reliability and homogeneity indicate that MOP20 possesses satisfactory psychometric properties. Instrument validity was checked by means of correlational analysis of the general achievement motive and dimensions of time perspective, self-efficacy and locus of control. The obtained correlation coefficients indicate a satisfactory validity of the scale MOP20, and are highly interpretable when explaining and considering the psychological space of the factors significant for achieving success in activities such as sports and entrepreneurship.

(Invited) A "Master Curve" for Plating Onset, Reaction Inhomogeneity during Fast Charging: Experiment and Theory

Inhomogeneous intercalation in porous anodes may lead to accelerated lithium plating during fast charging. This reaction inhomogeneity can occur both at the particle level or at the length scale set by the electrode thickness. Many studies have investigated the effects of various physical and electrochemical properties (e.g., ionic and mass transport, interface reaction kinetics, electrode thermodynamic behavior) on reaction inhomogeneity. However, their effect on accelerated lithium plating at high C-rates has not been fully elucidated. In this work, theory and experiment are used to study how reaction inhomogeneity and plating are related at high C-rates. It is shown that a non-dimensional number, the “reaction inhomogeneity parameter” λ, can be used to predict plating onset in graphite half-cells with a simple analytical solution derived from porous electrode theory, so long as anode particles are sufficiently small. Experiments measuring lithium plating onset in a small-particle graphite at various C-rates and thicknesses can be normalized to a single “master curve” for plating onset when plotted as a function of λ. These comparisons validate the theoretical predictions from both analytical and numerical modeling. Further, experiments with in situ visual inspection of local intercalation in graphite demonstrate that this λ parameter can predict reaction inhomogeneity measured using various metrics. These combined results support the numerical prediction that reaction inhomogeneity on the electrode length scale is responsible for accelerated plating at high charge rates for small-particle graphite. Further, it is shown with theory that this normalization procedure may be applicable for varied porosity, tortuosity, electrolyte materials and different anode materials. Finally, it is demonstrated that use of this “master curve” can be extended to patterned electrodes where channeled architectures are used to improve high C-rate charging.

The Effect of High-Pressure Homogenization Conditions on the Physicochemical Properties and Stability of Designed Fluconazole-Loaded Ocular Nanoemulsions.

The growing interest in high-energy emulsification is a result of its scalability, which is important from an industrial perspective and allows for a more reproducible and efficient production of pharmaceutical formulations. The aim of this study was to evaluate the effect of composition, mainly a fixed surfactant/cosurfactant (Smix) ratio, their concentration, and the parameters of high-pressure homogenization (HPH) processing on the quality and stability of ophthalmic fluconazole-loaded nanoemulsions. After a physicochemical analysis of nanoemulsions containing 20% w/w of oil, as optimal conditions for the HPH process, three cycles at a pressure of 1000 bar were established, obtaining formulations with an average droplet diameter size in the range of 80.63-129.68 nm and PDI values below 0.25. While it was expected that an increasing cosurfactant concentration decreased the droplet size, in the case of formulations containing Tween 20 and 10% w/w of cosurfactants, "over-processing" was observed, identified by the droplet size and polydispersity index increase. Consecutively, the selected formulations were evaluated for in vitro drug release in Franz's cell, antifungal activity, and 30-day stability using NMR spectroscopy. An antifungal activity test showed no significant difference in the antifungal activity between optimal fluconazole-loaded nanoemulsions and a 0.3% aqueous drug solution, but previously, research showed that prepared formulations were characterized by a higher viscosity and satisfactory prolonged release compared to a control. In a 30-day stability study, it was observed that higher HLB values of the used surfactants decreased the stability of the formulations in the following order: Kolliphor EL, Tween 80, Tween 20. The NMR spectra confirmed that Kolliphor EL-based formulations ensured the higher stability of the nanoemulsion composition in comparison to Tween 80 and a better stabilizing effect of propylene glycol as a cosurfactant in comparison to PEG 200. Therefore, the optimization of HPH technology should be focused on the selection of Smix and the Smix:oil ratio in order to prepare stable formulations of high quality.

Numerical simulation for MHD flow of Powell Eyring nanofluid with heterogeneous–homogeneous reactions, Arrhenius energy over a variable thickness stretching surface

The paper deals with the viscous incompressible flow of Powell Eyring type nanofluid over a variable thicker stretching surface induced by heterogeneous-homogeneous reaction and Arrhenius activating energy in a porous medium. Brownian motion and thermophoresis effect also considered to define flow regime. Boundary layer approximations of the governed flow are described by the partial differential equations which are laidback to handle by reducing them into coupled nonlinear ordinary differential equations. A MATLAB package BVP 4c is used to simulate the equations very contentedly to describe the behavior of several parameters graphically. Impact of several governing parameters are discussed. Rationality of the resolution is scrutinized by the comparison with previous literature in Tables 1 and 2. Numerical values of the Nusselt number and Sherwood parameters are discussed in Table 3. velocity profile diminishes for magnetic parameter, variable thickness, first slip and second slip parameters. while uplifted for mixed convection parameter. Temperature profile tumbling for Prandtl number and uplifted for radiation parameter, Brownian motion, thermophoretic effects, Grashof number and Magnetic field effects. Concentration profile declines for Schmidt number, chemical species and homogeneous heterogenous parameters.

LQG Graphon Mean Field Games: Analysis via Graphon-Invariant Subspaces

This paper studies approximate solutions to large-scale linear quadratic stochastic games with homogeneous nodal dynamics parameters and heterogeneous network couplings within the graphon mean field game framework in [2]-[4]. A graphon time-varying dynamical system model is first formulated to study the finite and then limit problems of linear quadratic Gaussian graphon mean field games (LQG-GMFG). The Nash equilibrium of the limit problem is then characterized by two coupled graphon time-varying dynamical systems. Sufficient conditions are established for the existence of a unique solution to the limit LQG-GMFG problem. For the computation of LQG-GMFG solutions, two methods are established and employed where one is based on fixed point iterations and the other on a decoupling operator Riccati equation; furthermore, two corresponding sets of solutions are established based on spectral decompositions. Finally, a set of numerical simulations on networks associated with different types of graphons are presented.

Mesoscopic thermal field reconstruction and parametrical studies of heterogeneous rock-filled concrete at early age

Rock-filled concrete (RFC) is a highly heterogeneous material composed of rock blocks and self-compacting concrete (SCC). There is still limited literature regarding the non-uniform thermal behavior of early-age RFC, making it difficult to predict equivalent homogeneous parameters. In this study, a novel mesoscopic FEM model was developed to simulate the full-scale heterogeneous RFC, both considering the pre-placement of stochastic rocks and layered filling process of SCC into rock voids. Based on on-site experiments of an integrally-poured RFC arch dam, the mesoscopic simulation results were validated and showed good accordance with the monitoring data. The results show that: (1) Spatial heterogeneity in RFC is most pronounced within the first 4 h after SCC pouring, and the RFC temperature typically reaches its peak within about 3 days. (2) The maximum temperature rise observed for SCC is only around 6∼7 °C, whereas the presence of the rockfill skeleton aids in the absorption of hydration heat, leading to a maximum temperature rise of 12.9 °C. (3) With a 5 % increase in the rock-fill ratio, the overall temperature level of the RFC model decreased by approximately 1 °C. (4) Increasing the adiabatic temperature rise of SCC by 10 °C, will lead to an approximate 3 °C rise in the highest temperature observed in RFC. These findings offer valuable insights for effective thermal control strategies in practical engineering applications.

Spontaneous supersymmetry breaking in inhomogeneous supersymmetric field theories and BPS vacua

We study spontaneous supersymmetry breaking in inhomogeneous extensions of N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 supersymmetric field theory models in 4-dimensions. The N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 Abelian Higgs model with the inhomogeneous mass parameter and the FI coefficient that are dependent on spatial coordinates, as well as the O’Raifeartaigh model with all its parameters being dependent on spatial coordinates, are studied in detail. In the presence of inhomogeneous parameters, half supersymmetry can be preserved by adding appropriate inhomogeneous deformations to the original Lagrangians. The inhomogeneous deformations often break the R-symmetry explicitly. In cases where the inhomogeneous deformations do not break the R-symmetry explicitly, we demonstrate that spontaneous breaking of the R-symmetry is infeasible. We argue that those models can not be spontaneous supersymmetry breaking models, according to the Nelson-Seiberg argument. We comment on this issue in the context of a generic N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 1 supersymmetric model as well.

COMPUTATIONAL STUDY OF UNSTEADY PULSATILE BLOOD FLOW THROUGH A POROUS MULTI-IRREGULAR VERTICAL STENOSED ARTERY: IMPACTS OF HOMOGENEOUS–HETEROGENEOUS REACTIONS

Homogeneous and heterogeneous reactions are significant because many chemically reactive systems, such as biochemical systems, involve both types of reactions. This paper sheds light on the effects of homogeneous–heterogeneous reactions on magnetohydrodynamic blood flow through the catheterized multi-irregular vertically stenosed artery in non-Darcy porous media. The governing partial differential equations are simplified using mild stenosis approximations and then transformed into the computational domain to simplify the numerical calculations. It has been noticed that the fluid velocity and the flow rate go to their maximum values after a short time, and they decrease with fluctuation in the case of pulsating, but in the case of nonpulsatile, the behavior is steady. Moreover, an increase in the homogeneous heat reaction parameter decelerates the blood velocity, the flow rate and elevates the fluid temperature. Furthermore, the concentration reaches the steady state faster in the absence of a homogeneous thermal reaction.

Data Freshness Optimization Under CAA in the UAV-Aided MECN: A Potential Game Perspective

As a promising enabler for edge intelligence, Unmanned Aerial Vehicles (UAV) have become more and more important in Mobile Edge Computing Networks (MECN), such as communication, computation, collection and control service supply. Although Age of Information (AoI) minimization is indispensable for fresh information collection and computation in the UAV-aided MECN, some attackers can launch attacks to deteriorate the availability of precious channel resources, such as revealed channel access attacks (CAAs). Moreover, recent research has not considered the system's active probability and security issues concurrently, e.g., CAA, in the average AoI minimization process. In this paper, to deal with this problem, we consider an AoI-oriented channel access problem under CAA with a game theory viewpoint. Firstly, to obtain a MECN-based AoI indicator under CAA, the system model with active probability consideration is established. Next, the channel access-based AoI minimization problem is formulated from the viewpoint of the Ordinary Potential Game (OPG). Furthermore, two algorithms called AACSD and DCASD are proposed to determine channel access strategies, by which the Nash Equilibrium (NE) solution of the OPG could be reached. Finally, experiments are conducted under homogeneous and heterogeneous parameter settings, and the simulation results evaluate the correctness and effectiveness of our proposals.

Cooperative security against interdependent risks

Firms in interorganizational networks are exposed to interdependent risks that are transferable across partner firms, such as contamination in food supply chains or data breaches in technology networks. They can be decomposed into intrinsic risks a firm faces from its own operations and extrinsic risks transferred from its partners. Firms have access to two security strategies: either they can independently eliminate both intrinsic and extrinsic risks by securing their links with partners or, alternatively, firms can cooperate with partners to eliminate sources of intrinsic risk in the network. We develop a graph‐theoretic model of interdependent security and demonstrate that the network‐optimal security strategy can be computed in polynomial time. Then, we use cooperative game‐theoretic tools to examine, under different informational assumptions, whether firms can sustain the network‐optimal security strategy via suitable cost‐sharing mechanisms. We design a novel cost‐sharing mechanism: a restricted variant of the well‐known Shapley value, the agreeable allocation, that is easy to compute, bilaterally implementable, ensures stability, and is fair. However, the agreeable allocation need not always exist. Interestingly, we find that in networks with homogeneous cost parameters, the presence of locally dense clusters of connected firms precludes the existence of the agreeable allocation, while the absence of sufficiently dense clusters (formally, k‐cores) guarantees its existence. Finally, using the SDC Platinum database, we consider all interfirm alliances formed in the food manufacturing sector from 2006 to 2020. Then, with simulated cost parameters, we examine the practical feasibility of identifying bilaterally implementable security cost‐sharing arrangements in these alliances.