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The transport properties of gas diffusion layer (GDL) in proton exchange membrane fuel cell are important parameters in fuel cell modelling, and one method to measure them is to simulate the transport of each species at spatial resolutions of a few microns in a microstructure of the GDL. One issue in this method is the size of the microstructure as using an unnecessarily big sample could substantially increase the computational cost. Both carbon-paper and carbon-cloth GDLs are investigated and their microstructures are obtained using numerical generation and X-ray micro-tomography respectively at a resolution of 1.733 µm. For each reconstructed GDL, we use the orthorhombic lattice Boltzmann model to simulate fluid flow through some subsamples taken from it in both the in-plane and the through-plane directions; the results show that the permeability of all subsamples is anisotropic in that their permeability in the in-plane direction is higher than in the through-plane direction. For each GDL, we compare its permeability calculated using samples of different sizes and find its representative elementary volume (REV) – a volume above which the calculated permeability represents the average ability of the GDL to conduct fluids. [ABSTRACT FROM AUTHOR]

A paper-based channel is a useful platform for the facile development of analytical devices implementing various chemical or biological reactions. To improve the analytical performance for various applications, it was necessary to analyze the detailed mixing characteristics within a paper-based channel. In this paper, we proposed a mathematical model to predict a concentration field created as a result of the imbibition of multiple fluids within a porous material. Interestingly, we found that the model exhibited a constant interdiffusion width within a paper-based channel even though the flow front velocity decreased over time. We were able to verify that our model accurately predicted the concentration field by comparing the experimental and numerical results for mixing in a 2 inlet-channel. Finally, we designed and fabricated paper-based channels to generate two (linear and non-linear) concentration gradients based on predictions made by the model. Both the experimental and numerical results were in good agreement, demonstrating that our model was accurate and useful for developing a paper-based analytical device utilizing the mixing characteristics of a sample and reagent flow system. [ABSTRACT FROM AUTHOR]

This study investigates roll paper fire using laboratory-scale experiments, with emphasis on water transport on burning surfaces for sprinkler suppression. Freeburn, water transport and suppression experiments were conducted using different types of paper with various basis weight and water absorptivity. For fire suppression, the experimental results showed different water transport patterns that are sensitive to the burning surface conditions. This is in contrast to the water transport under no fire conditions in straight vertical rivulets exhibiting highly non-uniform distribution along the roll perimeter. For roll paper fire growth, both surface delamination and exfoliation play a crucial role, with the delamination length increasing either linearly or exponentially with time and the exfoliation rates strongly dependent on paper basis weight. Although the effects observed at the small scale in this work may have differences from those at large scales, the experimental results yield insights for better understanding of fire growth and suppression mechanisms and provide extensive data for numerical model development and validation. [ABSTRACT FROM AUTHOR]

Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic–plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent. [ABSTRACT FROM AUTHOR]

Abstract A coupled numerical multi-physics model is developed to study the generation and variation mechanisms of friction torque, including fluid lubricating, micro-contact, sliding and heat transfer among the friction components. The engagement experiment is conducted to verify the accuracy of numerical model and investigate the stability of friction torque. The results show that the most significant operating factor affecting the friction stability is the applied pressure, followed by the rotating speed and the ATF temperature. Simultaneously, the operating factors have great influence on the torque response, engagement time and temperature rise. Moreover, the growth model of friction torque can be divided into two categories: one is increasing linearly and the other is concave parabolic rising. Highlights • A coupled numerical multi-physics model is presented to study the generation and variation mechanisms of friction torque. • The bench test is conducted to verify the accuracy of numerical model and investigate the stability of the friction torque. • The most significant operating factor affecting the friction stability is the applied pressure, followed by the rotating speed and ATF temperature. [ABSTRACT FROM AUTHOR]

A numerical model based on the Fokker–Planck equation for studying the orientation of paper fibers in a suspension is presented. The model is implemented in a finite volume framework. The rotational operators are discretized on a triangulated half sphere and the spatial operators are discretized on a Cartesian octree grid, where internal walls are handled with immersed boundary methods. Transient solutions of the two dimensional fiber orientation distribution are computed in the entire fluid domain. This is in contrast to earlier approaches that either only compute along streamlines or one dimensional projected orientations. The fibers are assumed to have negligible inertia and thus to follow the fluid perfectly and to be evenly distributed. A head-box geometry relevant for paper forming is used to exemplify the usefulness of the method. The influence of translational and rotational diffusion is included in the presented method. [ABSTRACT FROM AUTHOR]

Highlights • The problem concerns slip flow of carbon–water nanofluid. • Three non-dimensional parameters are wrong. • Some profiles are truncated and wrong. [ABSTRACT FROM AUTHOR]

Some errors exist in the above paper. [ABSTRACT FROM AUTHOR]

• Multiple evaluation methodologies used in retinal vessel segmentation identified. • Published scores in 100 papers categorized by the methodology they are based on. • The scores are numerically adjusted to eliminate the biases for comparability. • A new baseline ranking of segmentation techniques provided. • The comparison of incomparable scores is an ongoing phenomenon in the literature. [Display omitted] In the last 15 years, the segmentation of vessels in retinal images has become an intensively researched problem in medical imaging, with hundreds of algorithms published. One of the de facto benchmarking data sets of vessel segmentation techniques is the DRIVE data set. Since DRIVE contains a predefined split of training and test images, the published performance results of the various segmentation techniques should provide a reliable ranking of the algorithms. Including more than 100 papers in the study, we performed a detailed numerical analysis of the coherence of the published performance scores. We found inconsistencies in the reported scores related to the use of the field of view (FoV), which has a significant impact on the performance scores. We attempted to eliminate the biases using numerical techniques to provide a more realistic picture of the state of the art. Based on the results, we have formulated several findings, most notably: despite the well-defined test set of DRIVE, most rankings in published papers are based on non-comparable figures; in contrast to the near-perfect accuracy scores reported in the literature, the highest accuracy score achieved to date is 0.9582 in the FoV region, which is 1% higher than that of human annotators. The methods we have developed for identifying and eliminating the evaluation biases can be easily applied to other domains where similar problems may arise. [ABSTRACT FROM AUTHOR]

• We build a pairwise (PW) nonlinear fermi dynamics to study the rock-paper-scissors game's under evolutionary dynamics. • The model also investigates the effect of environmental noise and demographic noise. • We perform analytical analysis and numerical simulation to show the impact of linear and nonlinear to explore the noise effect. • Both linear and non-linear dynamics show comparable stability equilibria. The difference between conventional replicator dynamics and pairwise (PW) nonlinear Fermi dynamics can be discerned by studying the evolutionary dynamics of the interactions between the symmetric cyclic structure in the rock–paper–scissors game and inter- and intraspecific competitions. Often, conventional replicator models presume that the payoff difference among species is a linear function (a linear benefit). This study introduces a PW contrast under the properties of the well-known Fermi rule, where species play against one another in pairs. To model a PW nonlinear evolutionary environment (a nonlinear benefit) within this framework, both analytical and numerical approaches are applied. It is determined that the dynamics of the linear and nonlinear benefits can present the same stability conditions at equilibrium. Moreover, it is also demonstrated that, even in an identical equilibrium condition for both dynamics, the numerical result run by a deterministic approach presents a faster stability state for nonlinear benefit dynamics. This study also suggests that introducing mutation as demographic noise can effectively disrupt the phase regions and show the different relationships between linear and nonlinear dynamics. The symmetric bidirectional mutation among all the species reduced to the stable limit cycle by an arbitrary small mutation rate is also explored. Due to the environmental noise, however, linear and nonlinear exhibit the same steady state. Nevertheless, non-linearity illustrates more stable and faster stability situations. Our result suggests that environmental and demographic noise on the evolutionary dynamic framework can serve as a mechanism for supporting PW nonlinear dynamics in multi-species games. [ABSTRACT FROM AUTHOR]

Focal point of this review is to provide a comparative display of qualitative and quantitative methodologies employed for the appraisal of interacting energy and climate policies, underlying their key features while presenting the most critical issues and limitations not addressed so far. Qualitative approaches provide a descriptive explanatory analysis of often non-quantifiable process in policy interactions, whereas modeling approaches provide numerical data estimating the extent of policy interaction impacts. Quantitative methods work best for narrowly specified policy combinations, while contextual implications and cause-impact effects are explained further via qualitative ones. In addition most evaluations so far adopt a rational view of policies and policy interactions leaving out a systemic evaluation of the institutionalism of interacting policies. Research analysis of energy and climate policy interactions is still young in comparison to the broad field of policy evaluation and impact assessment. However infants inherently tend to grow. Endeavors for a methodological framework that would allow for a systematic exchange of data between qualitative and quantitative approaches and would also include the relevance of the context as well as key casual relationships behind policy combinations, would provide the basis for further growth of knowledge in the field. [ABSTRACT FROM AUTHOR]

• The compaction of paperboard is analyzed through finite element simulations of the industrial process. • The mechanisms governing the process are clarified within the rolling contact mechanics framework. • The parameters controlling the final product outcome are identified for industrial optimization. With the goal of partial or complete replacement of plastic components with paper-based products, 3D paper structures have seen a growing interest in industrial applications: from packaging to more complex daily life objects. However, the extensibility of paper has become a key issue within this context and is the main factor determining the formability of these products and determining the depth of the achievable shapes. The most effective way to increase paper's stretch potential is by subjecting the moist paper web to a compaction process, which can be achieved through an extensible unit that is located in the drying section of a paper machine, where the network experiences in-plane compression in the machine direction (MD), under out-of-plane lateral constraints. The objective of this work is to clarify the mechanisms governing the compression process and to evaluate the influence of various parameters on the final material properties to optimize the industrial production of extensible paper. The system operation has been simulated realistically and shows that paper experiences a compressive state passing through the nip, with plastic strains in MD direction being of the same order of the applied speed difference, which was expected experimentally in optimal conditions of compaction. Starting from an initial reference case, a sensitivity study has been performed to identify and address the following factors that may affect the compression state: (a) friction coefficients; (b) indentation level; (c) speed difference; and (d) rubber properties. The analysis of the numerical results gives an insight into the mechanisms governing the compaction operations and allows a better comprehension of the features controlling the process outcome. [ABSTRACT FROM AUTHOR]

• A robust hybrid controller by combining the advantages of the nonlinear backstepping controller and a super-twisting reaching law-based sliding mode controller will be formulated based on the developed model, which can ensure both the external disturbance rejection and faster transient performance. • This super-twisting reaching law can reduce the control signal amplitude to avoid saturation, which effectively reduces the chattering phenomenon in the control effort. • Guaranteeing the convergence of both voltage and current which in turn ensures the accurate tracking performance. • To show the effectiveness of the proposed controller in various system operating circumstances, simulation and experimental studies are conducted. This paper presents a robust hybrid super-twisting reaching law-based sliding mode controller in conjunction with a complementing recursive backstepping controller for DC-DC boost converters with constant power loads (CPLs). The key control goal is to keep the DC-bus voltage steady and constant while continuously powering the CPL. The nonlinear dynamical model of the DC-DC boost converter is translated into Brunovsky's canonical forms, utilizing the precise feedback linearization technique to attain this control goal. It is worth mentioning that the dynamical model has been modified with bounded external uncertainties to demonstrate the restraint performance for huge loads and input voltage variations. The proposed hybrid controller is then constructed using this model. Furthermore, to ensure the large signal stability of the whole system under the designed control law, the Lyapunov stability theory is used. Numerical simulation analysis are carried out in MATLAB/Simulink to validate the performance of the designed robust controller for a DC–DC boost converter feeding a CPL when the operating point change. The results show that the designed controller outperforms both existing nonlinear controllers and a traditional PI controller in terms of ensuring the system's stability and fast response in a variety of operating modes. Finally, in order to confirm the theoretical design and simulation results of the designed robust hybrid controller, experimental results are also provided in this paper. [ABSTRACT FROM AUTHOR]

This paper presents globally numerical properties of a new numerical scheme for a reaction-diffusion advection susceptible-infected-susceptible (SIS) model. A new numerical treatment technique is introduced in spatial discretization of advection-diffusion equation, which enables the numerical solutions to preserve the stability and positivity with less stepsize restrictions. The convergence, biological significance and globally stability of numerical solutions is explored in the paper. A threshold value, named by numerical basic reproduction number and denoted by R 0 Δ x , is introduced in the numerical stability analysis of the model. It is proved the numerical disease free equilibrium (DFE) is globally asymptotically stable if R 0 Δ x < 1 and unstable if R 0 Δ x > 1. It is shown the numerical basic number R 0 Δ x replicates the asymptotic behaviors of the basic reproduction number R 0 for the model. Some numerical experiments are given in the end to confirm the conclusions. [ABSTRACT FROM AUTHOR]

The mixed data sampling (MIDAS) model has attracted increasing attention due to its outstanding performance in dealing with mixed frequency data. However, most MIDAS model extension studies are based on statistical methods or machine learning models, which suffer from insufficient prediction performance and stability in small sample environments. To solve this problem, this paper proposes a novel mixed frequency sampling discrete grey model (MDGM(1, N)), which is a coupled form of the MIDAS model and discrete grey multivariate model. By adjusting the structure parameters, the model can be adapted to different sampling frequencies data, and degenerate into several types of grey models. Then, the unbiasedness and stability of the model are proved using the mathematical analysis method and numerical random experiment. The meta-heuristic algorithm is introduced to obtain the optimal weight parameters and the maximum lag order, improving the model's fitting ability to mixed frequency data. To demonstrate the effectiveness of the new model, a model evaluation system consisting of traditional evaluation metrics and a monotonicity test is established. Taking four hard disk drive failure datasets as research cases, the performance of the proposed model is compared with seven mainstream benchmark models. The results show that the proposed model has excellent applicability and outperforms other competition models in terms of validity, stability, and robustness. Furthermore, it is observed that the reported uncorrectable errors and the command timeout have a greater impact on hard disk drive failure. Finally, the new model is employed to forecast the failure of four hard disk drives. The forecasting results indicate that in the next four time points with a cycle of 21 days beginning in April 2023, the failure of the smaller capacity hard disk drives (0055 and 0086, corresponding to 8TB and 10TB) show a decreasing trend, reaching 67.442% and 89.7683%, respectively. The failure of the other larger capacity hard disk drives (0007 and 0138, corresponding to 12TB and 14TB) has increased, with a growth rate of 17.1016% and 123.7899%. [Display omitted] • A novel mixed frequency sampling discrete grey model is proposed. • The proposed model is proved to be unbiased and stable theoretically. • A Chimpanzee Optimization algorithm is introduced to globally search for weight parameters and maximum lag order. • A new model evaluation system for evaluating the effectiveness of prediction models is constructed. • The proposed model outperforms the other seven benchmark models in four case studies. [ABSTRACT FROM AUTHOR]

In this paper, a distributed bearing-based formation control scheme with finite-time convergency is proposed for multiple underactuated surface vessels (USVs). By virtue of the guide point-based model transformation method, the dimension of underactuated tracking error dynamics can be reduced from three to two. This allows us to convert the actuator model to a fully form that matches dimension-reduced tracking error dynamics. Further, to reduce the computation complexity, a finite-time recruited filter is designed according to first-order Levant differentiator. At meanwhile, auxiliary error compensation signals are introduced to address unknowns stemming from filter process and system dynamics. Since merely relative-distances and inner bearings are utilized in the proposed bearing-based formation approaches, the proposed control scheme provides a feasible solution to achieve formation control under body-fixed frame. Finally, theoretical analysis and numerical simulations are presented to demonstrate the efficacy. • Bearing-based finite-time formation control. • Underactuated surface vessels. • Levant differentiator. • Command filtered backstepping with error compensation signals and compensated errors. [ABSTRACT FROM AUTHOR]

Identifying the yarn end from the package surface is integral to the textile process. Using the automatic method based on negative pressure adsorption instead of the traditional manual method to capture the yarn end is an excellent solution to the time-consuming and inefficient problems caused by the latter. To clarify the influence of process parameters on the process of the yarn end being adsorbed to break away from the package surface by the suction nozzle, this paper first establishes a kinetic model of the yarn attached to the package surface. Next, the air-yarn interaction is solved using the momentum exchanged-based immersed boundary-lattice Boltzmann method (IB-LBM). Then, the effect of the distance between the suction nozzle and the package, the rotational speed of the package, and the airflow velocity in the suction nozzle duct on the movement of the yarn end with the airflow field are studied. Further, the regression model for the depth of the yarn end sucked into the suction nozzle duct when the package turns through a fixed angle is solved. Finally, with the goal of a high success rate, large distance, high efficiency, and energy saving, a multi-parameter optimization is performed using the Central Composite Design-based response surface methodology. The work has been proven effective through experimental validation and practical production applications. It provides a theoretical basis for the automatic process of yarn-end-capturing from the package in the textile field. • The kinetic model of the yarn end being adsorbed to break away from the package surface by airflow is established. • The air-yarn interaction is solved using the momentum exchanged-based immersed boundary-lattice Boltzmann method (IB-LBM). • The effects of several process parameters on the movement of the yarn end with the airflow field are studied emphatically. • Multi-parameter and multi-objective optimization are performed by the Central Composite Design-based response surface method. [ABSTRACT FROM AUTHOR]

The main aims of this paper are to investigate the existence and uniqueness results for the solution of an inverse source problem for a multidimensional, semilinear, backward parabolic equation, subject to Dirichlet boundary conditions, and to propose an iterative difference scheme for the numerical solution of the problem. The unique solvability of the difference scheme is established, as well. In the foundation of the theoretical results, some tools and facts from the operator theory, contraction principle and the Banach fixed-point theorem are applied. Furthermore, a comprehensive numerical analysis and several illuminating visualizations are carried out by employing the iterative difference schemes proposed on some test problems. [ABSTRACT FROM AUTHOR]

In this paper, we consider a two dimensional PDE model describing the proliferation-invasion structure of hypoxic glial cells in the brain, in which the cell movement is determined not only by natural diffusion but also, by the gradient of the concentration of oxygen. This model is given by a second order nonlinear system involving the density of cancer cells and the oxygen concentration, which are coupled by a chemoattraction term, a source of logistic growth, and a reaction term of Michaelis-Menten type. The contribution of this paper is summarized in the following two main aspects: first, we prove the existence and uniqueness of strong solutions; and second, we propose a nonlinear fully discrete finite element (FE) approximation for the model. We prove its well-posedness, some uniform estimates, the positivity for the discrete oxygen concentration and approximated positivity for the discrete tumour cells, which are required in this biological model. The key point to develop the numerical analysis is to control properly the second order nonlinear chemotaxis term as well as to obtain a discrete energy estimate which, in particular, gives a bounded energy; this energy estimate is derived by using a regularization technique. Finally, we present some numerical simulations which allow us to validate the theoretical results obtained. [ABSTRACT FROM AUTHOR]

In this paper, a dynamic model with two vibrator-driven pendulums is presented. Each pendulum is motivated by a pair of vibrators mounted on it. According to the deduced synchronization criteria of the pendulums and the vibrators, the synchronous states of pendulums are determined by the phase differences of vibrators. The two pendulums achieve anti-phase synchronization when the phase differences of arbitrary-two vibrators are all stabilized around zero. If the phase differences of the two vibrators mounted on the same pendulum are zero whereas those on different pendulums are π, the pendulums will arrive at the in-phase synchronous state. Besides, the system shows a relatively good isolative effect under the anti-phase synchronous motion of the two pendulums. Based on the theoretical results, some numerical qualitative analyses are presented and simulations are implemented for verification. The dynamic model in this paper can offer guidance to design a kind of vibrating jaw crusher. Here, the two pendulums serve as movable jaws and work by the anti-phase synchronous swing motion trajectory. [ABSTRACT FROM AUTHOR]

The pendulum model is a classic model in physics and has important theoretical and practical significance. In the actual application process of engineering, the characteristic that the simple pendulum has a tendency to always be stable towards the low side of the gravitational potential energy is often used to design the corresponding deformation mechanism as a sensing or control component. In this paper, a deformation structure of a simple pendulum based on this characteristic is analyzed, and a nonlinear dynamic model of the simple pendulum under variable damping is established according to the actual force analysis. Due to the complexity of its analytical solution, this paper adopts the method of numerical analysis to establish a simulation analysis model to analyze the motion pattern of the pendulum when the relative speed and direction of the pendulum and the damper are different and the damping force of the pendulum is different. [ABSTRACT FROM AUTHOR]

INCONEL® machining poses great challenges in predicting its behaviour, and exhaustive experimental evaluation of its machinability is expensive and unsustainable. Design of Experiments (DOE) can be performed without destroying components via Finite Element Analysis (FEA). However, it is paramount to establish if numerical modelling and the constitutive models can cope with an accurate predictability of INCONEL® machining. Hence, a broad review of FEA strategies will be given to systematically summarise and analyse the progress taken on INCONEL® machining predictability through FEA from 2013 to 2023 and present the most recent researchers' digital solutions, prospects, and limitations. Thanks to articles and books, this paper was conceived. The main keywords used in searching information were: "INCONEL® 718", "INCONEL® 625", "FEA", "Traditional Machining Modelling", "Johnson-Cook criteria", "ABAQUS™", "ANSYS®" and "DEFORM®". Combining these keywords was crucial to filter the current information about the evolution of INCONEL® alloy machining predictability through FEA. INCONEL® alloys FEA machining can nowadays effectively provide good quality and accurate results regarding the counterpart experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a performance degradation model based on empirical approaches, which can break down the power loss and quantify the influence of each aging phenomena from the overall performance degradation. With the presence of primary degradation mechanisms, the approach can be used to analyze the performance degradation of fuel cells under different degradation conditions. The aging parameters that represent hydrogen crossover, membrane resistance increase, and electrochemical active surface area (ECSA) loss are introduced to characterize the performance degradation. Based on the polarization behavior of proton exchange membrane fuel cells (PEMFCs), the variations of degradation stressors are determinated by fitting the aging parameters to the measuring polarization curves. The empirical approach is validated by a 150 h durability experiment and agrees well with all polarization curves. The results show that ECSA loss always maintains an apparent influence and hydrogen crossover accounts for 56% of the performance degradation in OCV. • An empirical approach is developed to analyze the durability of PEMFC. • The integrated effects of degradation stressors are considered. • Variations of degradation stressors during dynamic cycles are studied. • Voltage degradation due to various aging mechanisms is investigated. [ABSTRACT FROM AUTHOR]

In this paper, Er3+ doped TeO 2 -ZnF 2 -BaF 2 -KF-Ta 2 O 5 tellurite glasses with low hydroxyl content (∼0.03 × 10−19 cm−3) were investigated employing both glass composition and glass melting process optimization. The Raman spectra and physical properties were characterized to analyze the structure of the glasses. Under the pumping of 980 nm LD laser, intense up-conversion fluorescence at 1.5 and 2.7 μm of samples and their lifetimes were detected and analyzed, and the related transition mechanisms with gradient-varying Er3+ doping concentrations were discussed. The maximum absorption and emission cross section at 2.7 μm was calculated to be 6.4 × 10−21 cm2 and 6.8 × 10−21 cm2, correspondingly, which were higher than those of traditional tellurite glasses. Using the calculated and measured spectroscopic parameters of bulk tellurite glass, a dual-wavelength pumping model was established to verify the feasibility of mid-infrared laser output in similar tellurite glass fiber. Experimental results support the assertion that the Er3+ doped tellurite glasses hold promise as a candidate laser gain medium for mid-infrared fiber laser systems. [ABSTRACT FROM AUTHOR]

This paper carried out a high-temperature thermal gradient cycling test of ceramic matrix composites (CMCs), investigating the failure characteristics of CMCs in non-uniform high-temperature environments. The result shows that the damage characteristics of CMCs under thermal gradient environments are significantly different from those under uniform temperature environments. The SiC fiber pull-out lengths at different yarn fractures have obvious differences in the thermal gradient direction. The thermal stress damage propagation pattern of CMCs under the thermal gradient environment is revealed by numerical analysis, and its residual mechanical properties under different thermal gradient environments are predicted. The numerical results could be adopted as a theoretical basis and suggestions for temperature control of CMCs components in practical applications. [ABSTRACT FROM AUTHOR]

In order to understand and master the diffusion mechanism and spatial concentration distribution of hydrogen leakage in the engine room, this paper studies the diffusion behavior and concentration distribution of hydrogen under the coupling effect of multiple factors, and further explores the optimal installation location of the sensors. The results indicate that when the ventilation rate increases by 1, 2, and 3 times, the diffusion volume of hydrogen decreases by about 0.4, 0.5, and 0.6 times. The harm of the increase in leakage diameter is greater than the leakage pressure. And the temperature has a greater impact on the hydrogen volume fraction in areas below 4 % and a smaller impact on areas above 4 %. In this environment, the sensors should be installed at or above 5.5 m in the rear of the engine room and above the axis of the hydrogen transport pipeline interface, valves and other places prone to leakage. • Taking a ship engine room as the research object. • The influence of various factors on hydrogen distribution is compared. • The spatial concentration distribution of hydrogen leakage is analyzed. • Explored the installation position of the sensors. [ABSTRACT FROM AUTHOR]

In this paper, we address a class of boundary layer originated singularly perturbed parabolic reaction-diffusion problems with Robin boundary conditions having large time delay; for the higher order numerical analysis. The boundary layer originated nonuniform mesh, is generated by adaptive moving mesh approach based on equidistribution principle. The mesh is obtained by solving a nonlinear system; involving the discrete problem and the discrete nonlinear mesh generating functions. We provide the theoretical mesh structure. The difference scheme for Robin type boundary conditions having normalized flux; uses a combination of space and time discretizations so that the order of convergence in space is higher than the usual linear accurate upwind discretization in space. The present theoretical convergence analysis requires less regularity of the solution and proves to be exactly second order parameter uniform accurate in space. Numerical experiments highly validate the theoretical findings and also show that the present approach is better than the well-known upwind discretizations. [ABSTRACT FROM AUTHOR]

The energy sector is actively transitioning towards climate-neutral solutions, emphasizing advancements in clean power generation technologies. Cogeneration systems based on solid oxide fuel cells (SOFC) currently exhibit higher electrical efficiencies than conventional plants, but their operation can still be improved. One of the approaches to increase its efficiency is implementing anodic off-gas recirculation. In this work, a numerical model of a 10 kW SOFC installation with anodic gas recirculation was analyzed using Aspen HYSYS software. System fueled with three alternative fuels (natural gas, hydrogen, and ammonia) was tested. In this paper it was proven that anode-off gas recirculation improves the electrical and total efficiency of the system for each fuel type. The cogeneration unit with a SOFC stack can operate safely over a wide range of recirculation ratios without need for additional modifications. Ammonia-fueled units achieve electrical efficiency (55%) higher than hydrogen-based system (47.6%) but lower than installation fueled with natural gas (61.8%). • Anode off-gas recirculation in combined heat and power based on SOFC was studied. • Three fuels where considered: nautral gas, hydrogen and ammonia. • Wide range of recirculation can be achieved for all three fuels without modification. • Optimal recirculation ratio was found for each fuel and stack fuel utilization factor. • Highest electrical efficiency of up to 61.8% is achieved for natural gas fueled system. [ABSTRACT FROM AUTHOR]

The present paper studies Love-type wave propagation in a fluid-saturated fractured poro-viscoelastic layer sandwich between a coated elastic layer and a non-homogeneous anisotropic Voigt-type viscoelastic half-space. The interfaces between the layers and the half-space are considered as sliding contacts with two different sliding parameters. An impulsive point source is located at a varying depth in the intermediate poro-viscoelastic layer in the form of the Dirac-delta function. The vertical non-homogeneity in the half-space is assumed to be a combination of linear and exponential functions that vary with depth in the medium. Using the Fourier transforms and Green's functions, the equations of motion, in the form of partial differential equations, are solved analytically. An appropriate boundary condition is used to accomplish this. The closed form of the complex dispersion equation has been obtained by assuming that the wavenumber is in the form of a complex quantity. The validity of our model has been examined using several specific cases and compared to the classical Love wave equation. Numerical and graphical analyses of dispersion and displacement were performed using MATLAB software. It has been found that a single porous medium has a higher Love-type phase velocity than a double porous medium. Additionally, the sliding parameters increase the range of wavenumber when there is no phase velocity. An inverse relationship was found between the depth of the point source and the particle displacement in the coated layer. In addition to contributing to our understanding of geophysical phenomena and subsurface explosions, these findings may provide insight into the inner structure of the planet. • Layered media with sliding contacts are introduced. • The coupled Green's function approach is used for Love-type dispersion. • Wavenumbers for non-existence of phase velocity increase with sliding parameters. • An inverse relationship is found between the depth of the point source and the particle displacement in the coated layer. [ABSTRACT FROM AUTHOR]

Plasma gasification technology is a harmless and resourceful solid waste treatment method. As a hazardous waste, studying the plasma gasification treatment of oil-based drilling cuttings has practical significance. Therefore, this paper uses Aspen Plus to establish a plasma gasification model. Based on model validation, the effects of input power, oxygen equivalence ratio, and carrier gas type on the plasma gasification process of oil-based drilling cuttings were discussed. In addition, by designing a quadratic regression orthogonal experiment, a nonlinear quadratic regression equation was established between the three factors of gasification pressure, input power, and equivalence ratio, as well as different gasification indicators, namely gas yield, lower heating value, and gasification efficiency. By solving the equation, it was found that when the gasification power is 70 kW, the gasification pressure is 10 atm, and the equivalence ratio is 0.1, the gas yield reaches its maximum of 0.74 kg/m3; When the gasification power is 15 kW, the gasification pressure is 10 atm, and the equivalence ratio is 0.1, the lower heating value of gas production reaches its maximum of 9.68 MJ/m3; When the gasification power is 15 kW, the gasification pressure is 1 atm, and the equivalence ratio is 0.1, the gasification efficiency reaches its maximum of 37.6%. At the same time, it was found that the influence of gasification pressure, input power, and equivalence ratio on gasification indicators was ranked in descending order as equivalence ratio, input power, and gasification pressure. The above research provides certain reference values for the practical operation of plasma gasification of oil-based drilling cuttings. • Analyzed the effects of different factors on plasma gasification of OBDC. • Optimum parameters of plasma gasification of OBDC are studied. • Ranked the degree of influence of different factors on plasma gasification of OBDC. • Analyzed the efficiency of plasma gasification of OBDC. [ABSTRACT FROM AUTHOR]

This paper considers a large-scale multiple testing problem for spatiotemporal data with multiple change points. A data-driven procedure that aims to fully utilize the clustering information is proposed. Specifically, we first develop a new change-point detection algorithm that integrates the kernel-based aggregation of spatial observations with a global loss function at the temporal level to group data into several sets, and then derive an FDR control scheme for set-wise multiple testing. Under some mild conditions on the spatiotemporal dependence structure, FDR is shown to be strongly controlled. Theoretical analysis and numerical studies demonstrate the advantages of the algorithm over competing methods. [ABSTRACT FROM AUTHOR]

• New curvature Euler-Bernoulli and Timoshenko beams based on the couple stress and its flexoelectric theory are presented. • Analytical solutions for bending and free vibration of Euler-Bernoulli and Timoshenko nanobeam are derived. • An IGA is developed for extending the applicability of the curvature-based flexoelectric nanobeam. • The accuracy of analytical solution is verified through IGA numerical solutions. • The flexoelectric effects, microstructure effects and boundary conditions on mechanical behavior of nanobeams are studied. In this paper, new curvature-based flexoelectric Euler-Bernoulli and Timoshenko beam models are derived based on the couple stress and its flexoelectric theory. These models consider both the microstructure and flexoelectric effects. The governing equations and boundary conditions are obtained using the variational formula of Hamilton's principle. Analytical solutions for the static bending and free vibration problems of Euler-Bernoulli and Timoshenko beam models with a simply supported nanobeam are presented. To extend the applicability of the curvature-based flexoelectric beam models, an isogeometric analysis (IGA) numerical approach which satisfy the needs of C 1 continuity is developed. Numerical results are provided to verify the accuracy of the analytical and IGA numerical solutions, and the influence of flexoelectric effects, microstructure effects and boundary conditions on the mechanical behavior of nanobeams is analyzed. [ABSTRACT FROM AUTHOR]

Only rigorous evaluation of competence will result in the production of safe surgeons that are able to provide the best care for patients. The development of competency-based assessment should ultimately be evidence driven. Explore the volume of existing evidence pertaining to the different objective assessment methods reported in the literature. Studies describing objective assessment of postgraduate general surgical trainees within the last 20 years. PubMed, Ovid Medline and Web of Sciences. A data chart proforma was designed and data were extracted into tables. Basic numerical analysis of extracted data and narrative synthesis of charted data. A total of 343 papers were reviewed. 26 were eligible for inclusion. 92% of articles were published from 2008 onwards. 50% have been published in the last five years. The articles originated from 6 different countries, predominantly the United Kingdom (42%), followed by the United States of America (38%). In addition, a small number were published from Canada (8%), Japan (4%), Germany (4%) and Australia (4%). UK publications were predominantly between 2008 and 2014 while the USA had a later predominance between 2015 and 2018. 42% were based on quantitative methodology, 27% had a qualitative approach while 31% had mixed analysis. There were sixteen assessment methods presented. The most common type of assessment was Objective Structured Assessments (27%), which included Objective Structured Assessment of Technical Skill (OSATS) (23%) and Objective Structured Assessment of Non-Technical Skill (4%). Procedure Based Assessment (PBA) (23%) and Entrustability Scales (23%) were also prevalent. This scoping review has identified a range of different assessment methods. The assessment methods with a higher volume and level of supporting evidence were OSATS, PBAs and Entrustability Scales. There was a lower volume and level of supporting evidence found within this review for the remaining assessment methods. • Explore volume of existing evidence pertaining to objective assessment methods. • Studies of assessment of postgraduate general surgical trainees in last 20 years. • 343 papers reviewed; 26 included. Numerical analysis/narrative synthesis performed. • Articles originated from UK (42%), USA (38%), Other (20%). • 16 assessments presented: OSA (27%), PBA (23%), Entrustability Scale (23%), Other (27%). [ABSTRACT FROM AUTHOR]

This paper explores the numerical analysis of a model for the challenging childhood disease named Rotavirus, by examining the impact of reducing risk. Specifically, the numerical approximation solution of the rotavirus model is investigated using three different numerical methods; the Runge-Kutta-Fehlberg technique, differential transformation method, and the Laplace Adomian decomposition method. The effectiveness and accuracy of these methods are compared, and conclusions are drawn regarding their suitability for obtaining approximate solutions to modeling problems. Additionally, the effect of reducing the risk of infection on the susceptible and vaccinated populations has been studied, leading to interesting findings. This research provides valuable insights into the application of numerical methods to model infectious diseases and may be useful for researchers. • Numerical analysis of a rotavirus model. • Examining the impact of reducing risk. • The study examines numerical solutions for the rotavirus model using techniques like Runge-Kutta-Fehlberg, differential transform method, and Laplace Adomian decomposition method. • The numerical simulations were computed at varying time intervals. • The effect of reducing the risk of infection on the susceptible and vaccinated populations is examined and investigated. [ABSTRACT FROM AUTHOR]

This paper investigates the attitude coordination control issue for spacecraft formation flying in the presence of actuator saturation and external disturbances with unknown boundaries. Firstly, a super-twisting integral terminal sliding mode surface is developed, which ensures that the sliding mode surface and its first-time derivative converge to zero in finite time. Then, based on the developed sliding mode surface and adaptive technique, a robust anti-saturation distributed attitude coordination controller that enables the attitude and angular velocity to precisely track the desired time-varying command in finite time is devised under the undirected communication topology. Finally, stability analysis and numerical simulations validate the effectiveness and feasibility of the devised control approach. [ABSTRACT FROM AUTHOR]

In this paper, we study a class of problems known in the literature as jump Pearson diffusions, for which asymptotic mean and variance are closed-form deductible. This makes the problem very attractive from a numerical analysis point of view, in terms of testing the conservative properties of available numerical methods. In particular, we introduce a complete analysis for the class of the stochastic θ -methods on their ability to replicate the asymptotic behavior of the first and second moments of the exact solution. Finally, selected numerical experiments are provided to confirm the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]