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In this article, we present a mathematical model and numerical simulation of the coffee-ring effect on porous papers. The numerical method is based on Monte Carlo simulation. The proposed model is simple but can capture the main mechanism of coffee stain formation on porous papers. Several numerical experiments are presented to demonstrate the performance of the proposed algorithm. We can obtain the coffee-ring effect on porous papers as the computer simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a brief overview of the use of magnetic field in studying droplet adhesion to a fiber or a fibrous surface. The paper starts by discussing ways to quantify the force required to detach a droplet from a fiber for its applications in coalescence filtration, i.e., removal of dispersed droplets from a gaseous or liquid flow using a fibrous filter. It then continues to discuss droplet detachment from a fibrous surface or penetrating into a thin fibrous coating. The emphasis is put on a recently develop magnetic approach for measuring force of detachment and on its novel simplicity and non-intrusive nature in the context of existing droplet detachment methods. Our review also includes a discussion on force of detachment for multiphase droplets comprised of two immiscible liquids, i.e., compound droplets. Atomistic- and continuum-level numerical simulations pertaining to droplet detachment are also discussed throughout the paper when appropriate. [ABSTRACT FROM AUTHOR]

In this paper, the effects of different designs of pressure vessels on hydrodynamic parameters and the performance of seawater RO systems are investigated using computer simulations. Simulation results showed that designs using pressure vessels with four membranes in two-pass RO systems have a lower energy consumption, 5.29 and 0.33 kWh/m3 for the first and second passes, respectively, than those with two or three membranes. Also, designs No. 4 and No. 10 were the most efficient, 41 and 56% for the first and second passes, respectively, compared to other ones. The first and second passes required a lower permeate and feed pressure when using designs No. 3, No. 6, No. 9, and No. 12 where pressure vessels with two membranes were used. In addition, hybrid designs of two-pass RO systems were found to have the best efficiency and the lowest energy consumption among various other designs. Findings showed that in two-pass RO systems, the first pass consumes more energy than the second pass. Thus, the efficiency of the second pass in all designs of two-pass RO systems is more than the first pass. The results presented in this paper can be used to optimize the design of two-pass RO systems to ensure the optimum operation of such systems. [ABSTRACT FROM AUTHOR]

Several real-life problems that involve a time delay are modeled using fractional time-delay systems. However, most studies related to these systems assume that the delay is already known, which is not the case in practical scenarios where the delay is often uncertain or unknown. To address this issue, this paper proposes an algebraic and robust method to estimate the input delay for a class of fractional time-delay systems in a noisy environment, by applying a cross-convolution approach. Besides, a filtering methodology is incorporated with the proposed approach to enhance its efficacy. In addition, this paper presents novel theories on convolution in the field of fractional calculus. Finally, the performance of the proposed approach is demonstrated by numerical simulations. [ABSTRACT FROM AUTHOR]

This paper considers theoretical foundations and mathematical methods of data analysis under the conditions of the Rice statistical distribution. The problem involves joint estimation of the signal and noise parameters. It is shown that this estimation requires the solution of a complex system of essentially nonlinear equations with two unknown variables, which implies significant computational costs. This study is aimed at mathematical optimization of computer algebra methods for numerical solution of the problem of Rician data analysis. As a result of the optimization, the solution of the system of two nonlinear equations is reduced to the solution of one equation with one unknown variable, which significantly simplifies algorithms for the numerical solution of the problem, reduces the amount of necessary computational resources, and enables the use of advanced methods for parameter estimation in information systems with priority of real-time operation. Results of numerical experiments carried out using Wolfram Mathematica confirm the effectiveness of the developed methods for two-parameter analysis of Rician data. The data analysis methods considered in this paper are useful for solving many scientific and applied problems that involve analysis of data described by the Rice statistical model. [ABSTRACT FROM AUTHOR]

Mobile manipulator robots that combine mobile platforms and robotic arms have been attracting considerable attention in recent years. In this paper, the motion control problem of the mobile manipulator system is considered with the following proposed control strategy. Firstly, a decoupled dynamic model is created to increase operation safety and to reduce complexity such that the independent controllers can be designed for the mobile system and the manipulator system. Subsequently, an effective reference trajectory generator is proposed to guide the mobile manipulator systems to the proper position for the manipulation being able to grip the target. Thereafter, the fuzzy controllers are designed for the mobile system to eliminate the tracking error and for the manipulator system to accomplish the gripping mission. The stability of the mobile manipulator control system can be guaranteed by the Lyapunov theory. Finally, the numerical simulations are given to demonstrate the effectiveness of the proposed approach. From the simulation results, it can be seen that this paper as well as other compared methods have good control response in case of small controller gain, in which the convergence time are about 4–5 s. However, by increasing the controller gain to improve the control response, the other methods will make the system unstable or the controller output will produce a large amount of chattering. The proposed controller in this paper can not only decrease the convergence time, from 5 to 3 s, but also provide a smooth control response. [ABSTRACT FROM AUTHOR]

Burden is one of the major influencing blast design parameters which should be optimised for the extraction of narrow vein ore bodies. Numerical simulation-based approach has been used for the optimisation of burden in this paper. Different models were prepared under varying parametric conditions including width of the vein, blasthole diameter and burden. The RHT concrete constitutive model was used for the analysis of damage contour. The volume of the excavated rock along the free face (EV) was quantified from the model output in all the scenario. The study showed that EV initially increases with the increase in burden for a particular width of vein. Furthermore, EV starts decreasing after a point termed as pivot point. The value of burden at this pivot point was considered as optimal in this study. The best fit curve between EV and burden for three blasthole diameter and seven different width of vein were plotted. In all instances, the outputs of the model followed the second-degree polynomial equation. The study also suggests that the optimum burden reduces with the increase in the width of the vein. It has also been found that the optimum burden follows power trend with the increase in width of the ore body irrespective of blasthole diameter. Based on the optimum burden obtained from the output of simulation along with different blasthole diameter and width of the ore body, an empirical relationship has been established. The developed empirical relationship has a good agreement with the experimental trial data. Highlights: Numerical simulation technique has been used in this paper for the optimisation of burden while extraction of narrow vein stopes. The study suggest that the relation of volume of the excavated rock along the free face and burden is second-degree polynomial in nature. It has been found that the optimum burden for narrow vein is higher as compared to wider width ore body. Study also suggest that optimum burden follows power trend with the increase in width of ore body. The influence of width of the ore body in the selection of burden vanishes after certain width of ore body as per the observation of model output. [ABSTRACT FROM AUTHOR]

Loop-mediated isothermal amplification or LAMP has been identified to be an efficient technology for point-of-care diagnostics. Paper-based LAMP technique has tremendous potential in replacing the existing tube-based technology as the manufacturing cost of a paper-based device is comparatively lower and easy-to-use. LAMP-based paper diagnostic device for Mycobacterium tuberculosis (MTB) detection is of extreme importance as it will help in early and rapid diagnosis of the affected patients. The fabrication of these devices requires assessment of design parameters on the extent of LAMP amplification reaction. Hence, CFD studies would be extremely beneficial from the design perspective. The current work presents an insight into the CFD simulations for LAMP amplification reaction on a porous paper membrane (nitrocellulose membrane). The convection-diffusion-reaction model is solved on a COMSOL Multiphysics 5.0 platform. Studies on effect of pore size, aspect ratio and initial DNA concentration on the extent of DNA amplification reaction have been carried out. The current paper-based technique is effective in detecting a minimum of 5 copies of DNA contrasting the previous semi-quantitative technique which demonstrated the detection of minimum 98 copies. Overall, the simulation results displayed almost 96% enhancement in the DNA amplification rate on paper membrane. Graphical abstract Graphical abstract for the computational study of DNA amplification reaction via LAMP technique on a porous paper membrane. [ABSTRACT FROM AUTHOR]

We outlined earlier in this journal by means of finite element simulations how patterns of normal faults arise by a synsedimentary tectonic extension, and how clay smears evolve therein. In the present paper, we show how hydraulic breakthroughs of clay smears can arise so that water, gas and mud rise in faults. Mechanical properties of sand and clay are introduced first for the stable range and then for rupture and internal erosion. Our numerical simulations for the evolution of normal faults and clay smears are discussed in light of critical phenomena. Water assembled in an open-cast mine about 20 years ago as the critical hydraulic gradient in a clay smear dropped to the actual one due to the rapid excavation-induced deformation. The latter led to a critical point under an excavation the slope of which was parallel to a nearby normal fault. Clay smears can also break by earthquakes so that the critical hydraulic gradient drops to the actual one caused by methane with an excess pressure. This can lead to hydraulic breakthroughs and cold eruptions at outcrops of faults. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of spatio-temporal dynamics for a time-space periodic population growth model with impulsive birth. We first formulate a discrete-time semiflow by the 1-year solution map, and obtain a threshold-type result for the semiflow with spatially periodic initial data. Then we establish the existence and the computational formulas of the spreading speeds and prove the coincidence of the spreading speeds with the minimal speeds of spatially periodic traveling waves in the monotone case. Further, we investigate the global dynamics of this model in a bounded spatial domain. Finally, we conduct numerical simulations to verify our analytical results and illustrate some interesting findings. [ABSTRACT FROM AUTHOR]

Typhoons are recurring meteorological phenomena in the southeastern coastal area of China, frequently triggering debris flows and other forms of slope failures that result in significant economic damage and loss of life in densely populated and economically active regions. Accurate prediction of typhoon-triggered debris flows and identification of high-risk zones are imperative for effective risk management. Surprisingly, little attention has been devoted to the construction of physical vulnerability curves in typhoon-affected areas, as a basis for risk assessment. To address this deficiency, this paper presents a quantitative method for developing physical vulnerability curves for buildings by modeling debris flow intensity and building damage characteristics. In this study, we selected the Wangzhuangwu watershed, in Zhejiang Province of China, which was impacted by a debris flow induced by Typhoon Lekima on August 10, 2019. We conducted detailed field surveys after interpreting remote sensing imagery to analyze the geological features and the mechanism of the debris flow and constructed a comprehensive database of building damage characteristics. To model the 2019 debris flow initiation, entrainment, and deposition processes, we applied the Soil Conservation Service-Curve Number (SCS-CN) approach and a two-dimensional debris flow model (FLO-2D). The reconstructed debris flow depth and extent were validated using observed debris flow data. We generated physical vulnerability curves for different types of building structures, taking into account both the degree of building damage and the modeled debris flow intensity, including flow depth and impact pressure. Based on calibrated rheological parameters, we modeled the potential intensity of future debris flows while considering various recurrence frequencies of triggering rainfall events. Subsequently, we calculated the vulnerability index and economic risk associated with buildings for different frequencies of debris flow events, employing diverse vulnerability functions that factored in uncertainty in both intensity indicators and building structures. We observed that the vulnerability function utilizing impact pressure as the intensity indicator tends to be more conservative than the one employing flow depth as a parameter. This comprehensive approach efficiently generated physical vulnerability curves and a debris flow risk map, providing valuable insights for effective disaster prevention in areas prone to debris flows. [ABSTRACT FROM AUTHOR]

The objective of this paper is to designed a nonuniform arrangement of elliptical holes for film cooling (FICO) on gas turbine blades. The optimal distance between rows of holes (1–3) was determined to maximize FICO effectiveness. The three-dimensional geometry of the problem (Circle, horizontal elliptic, and vertical elliptic) was modeled based on an existing experimental sample. The turbulent steady-state incompressible single-phase flow was modeled using conservation equations and considering the blowing ratio (0.25–2), adiabatic FICO efficiency, von Mises stress (VMS), and hydraulic radius relationships. Results showed that elliptical holes with a major diameter normal to the flow had the highest centerline and laterally averaged effectiveness values. Additionally, holes that were more laterally stretched out had higher efficiency. The best effectiveness was achieved at an optimal blowing ratio of 0.75. Furthermore, the maximum von Mises stress was higher in cases with smaller distances between rows. Von Mises stress analysis revealed that elliptical openings with a large diameter perpendicular to the flow caused the lowest thermal stress in the solid body. When cooling with three rows of elliptical holes, a larger distance between the second and third rows resulted in higher effectiveness and lower maximum VMS at an optimal distance. [ABSTRACT FROM AUTHOR]

In this paper, we study discrete-time quantum walks on Cayley graphs corresponding to Dihedral groups, which are graphs with both directed and undirected edges. We consider the walks with coins that are (real) linear combinations of permutation matrices of order three. We show that the walks are periodic only for coins that are permutation or negative of a permutation matrix. Finally, we investigate the localization property of the walks through numerical simulations and observe that the walks localize for a wide range of coins for different sizes of the graphs. [ABSTRACT FROM AUTHOR]

This paper represents a unique approach to augment the security of iris images by utilizing twin decomposition techniques in a hybrid transform domain, coupled with a rear-mounted spiral phase mask. To introduce non-linearity into the scheme, the amplitudes of input iris image pixels are squared, and the QZS algorithm is employed to translate two-channel input iris images into a single channel for convenience, thereby escalating the key space of the proposed scheme. The amalgamation of Fresnel transform, and hybrid transform develops a distinctive combination. The techniques of random decomposition and unequal modulus decomposition are employed to strengthen the system against attacks based on iterative transformations. Adding an extra layer of security, a spiral phase mask mounted at the back addresses the problem of the second lens becoming invalid in the traditional double random phase mask scheme. This approach combines both public and private keys, making it asymmetric in nature. MATLAB based numerical simulations have been executed to confirm the performance of the presented mechanism, concentrating on key sensitivity, statistics, and resistance to attacks aspects. The proposed scheme proves to be effective against various types of attacks, such as noise, classical, and special attacks, while also displaying heightened sensitivity to various keys and parameters. [ABSTRACT FROM AUTHOR]

In this paper, the optimal formation control issue with collision avoidance and connectivity assurance is investigated for a class of second-order uncertain nonlinear multi-agent systems. First, the neural networks are employed in order to deal with the unknown nonlinear dynamics of the system. Then, an optimal formation control scheme is developed in the framework of the identifier–actor–critic. By constructing a new performance metric function containing collision avoidance and connectivity constraints, it is demonstrated that asymptotic convergence of the tracking error can be achieved under the proposed control scheme. Finally, the effectiveness of the proposed control method is validated by the numerical simulation example. [ABSTRACT FROM AUTHOR]

The paper presents research on identifying a biomechanical parameter from a theoretical model of changes during osteoarthritis. In vitro experiments were carried out on quasi-3D chondrocyte cultures seeded on corn-starch hydrogel materials and subjected to mechanical stress on a designed and constructed stand. The results were adapted to a mathematical model and calculated on a simplified two-dimensional specimen. Numerical simulations have been performed to illustrate the growth of bone spurs. The observed changes of variables which determine osteophytes are qualitative and more correlated to the real-life observations. [ABSTRACT FROM AUTHOR]

In the case of multicollinearity, biased estimators are always introduced to correct the least squares estimator. In this paper, we propose a new biased estimator for the restricted linear model. The properties of the new estimator and its superiority over the restricted least squares estimator in terms of the mean square error and Pitman closeness criterion are theoretically analysed. Furthermore, we optimize and verify the feasibility of the new estimator using a numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper, we consider the partial linear regression model yi = xiβ* + g(ti) + εi, i = 1, 2, ..., n, where (xi, ti) are known fixed design points, g(·) is an unknown function, and β* is an unknown parameter to be estimated, random errors εi are (α, β)-mixing random variables. The p-th (p > 1) mean consistency, strong consistency and complete consistency for least squares estimators of β* and g(·) are investigated under some mild conditions. In addition, a numerical simulation is carried out to study the finite sample performance of the theoretical results. Finally, a real data analysis is provided to further verify the effect of the model. [ABSTRACT FROM AUTHOR]

In this paper, we propose and analyze a nonautonomous model that describes the dynamics of a size-structured consumer interacting with an unstructured resource. We prove the existence and uniqueness of the solution of the model using the monotone method based on a comparison principle. We derive conditions on the model parameters that result in persistence and extinction of the population via the upper-lower solution technique. We verify and complement the theoretical results through numerical simulations. [ABSTRACT FROM AUTHOR]

Direct numerical simulation (DNS) of turbulent wall-bounded flows requires long streamwise computational domains to establish the correct spatial evolution of large-scale structures with high fidelity. In contrast, experimental measurements can relatively easily capture large-scale structures but struggle to resolve the dissipative flow scales with high fidelity. One methodology to overcome the shortcomings of each approach is by incorporating experimental velocity field measurements into DNS as an inflow boundary condition. This hybrid approach combines the strengths of DNS and experimental measurements, allowing for a reduction in the streamwise computational domain and accelerated development of large-scale structures in turbulent wall-bounded flows. To this end, this paper reports the results of an investigation to establish the impact of limited spatial resolution and limited near-wall experimental inflow data on the DNS of a wall-bounded turbulent shear flow. Specifically, this study investigates the spatial extent required for the DNS of a turbulent channel flow to recover the turbulent velocity fluctuations and energy when experimental inflow data is typically unable to capture fluctuations down to the viscous sub-layer or the smallest viscous scales (i.e. the Kolmogorov scale or their surrogate viscous scale in wall-bounded turbulent shear slows) is used as the inflow to a DNS. A time-resolved numerically generated experimental field is constructed from a periodic channel flow DNS (PCH-DNS) at R e τ = 550 and 2300, which is subsequently used as the inflow velocity field for an inflow–outflow boundary conditions DNS. The time-resolved experimental inflow field is generated by appropriately filtering the small scales from the PCH-DNS velocity by integrating over a spatial domain that is representative of a particle image velocimetry interrogation window. This study shows that the recovery of small scales requires a longer domain as the spatial resolution at the inflow decreases with all flow scales recovered and their correct scale-dependent energy is re-established once the flow has developed for 3 channel heights. [ABSTRACT FROM AUTHOR]

Empirical and probabilistic risk analysis methods can relatively accurately predict the seismic vulnerability of reinforced concrete (RC) structures. Using various intensity measures to estimate and forecast the seismic hazard of RC structures can contribute to the development of typical structural seismic resilience and vulnerability models. However, traditional empirical and analytical vulnerability studies rely more on field observation data and seismic risk algorithms and less on numerical simulation analysis for validation and optimization, resulting in limitations and fuzziness in the accuracy of the developed structural risk models. To explore the damage modes of RC frame structures under different intensities, this paper innovatively combines numerical model algorithms with empirical vulnerability methods to conduct empirical vulnerability and numerical simulation analyses on RC structures. Using probability statistics and nonlinear regression analysis methods, a prediction model for estimating the fragility of RC structures was proposed, and 858 RC structure damage samples from a typical city (Dujiangyan) during the Wenchuan earthquake in China on May 12, 2008, were used for model verification and comparative analysis. Using seismic response analysis theory, 901,530 acceleration records of the Wenchuan earthquake detected by eight actual seismic stations were selected, and nonlinear dynamic time history analysis was conducted. A four-story RC structural model was established using finite element software, and numerical simulation analysis was conducted on the model using 117,863 real earthquake acceleration data points obtained from actual monitoring stations during the Wenchuan earthquake. The acceleration time history curves and incremental dynamic analysis curves of the RC structure under different intensity measures were generated. By combining the moire algorithm and numerical simulation technology, damage stress clouds of steel bars and concrete under different intensity measures were generated, and the accuracy of the developed empirical vulnerability model was verified via numerical simulation results. [ABSTRACT FROM AUTHOR]

The process of heat transfer is one of the most important issues in the food industry and plays a crucial role in the storage of frozen foods. The main objective in this field is to extend the storage time, which can be achieved by limiting the heat transfer between the ambient air and the frozen food product. In this paper, the authors applied a numerical model of the phase change process to simulate the freezing and thawing process of a package wrapped with compressible multilayer polymer thermal insulation. The model was solved in COMSOL Multiphysics program and verified with experimental results with satisfactory agreement. Based on the performed simulations and experiments, it was proved that the freezing time of the tylose package is almost the same regardless of the applied film, while the thawing time of the package strongly depends on the type of film—transparent, opaque or metallized. The use of transparent film allows to extend the maximum thawing time of food products by 2 times, the use of opaque film—by about 3.7 times, and the use of metallized film—by about 4.1 times. [ABSTRACT FROM AUTHOR]

In this work, the well-known Ince–Gaussian beams (IGBs) are reproduced by expanding them in the Laguerre Gaussian basis. The established formula will derive the analytical expression of the average intensity of the IGBs propagating through the turbulent atmosphere by using the extended Huygens–Fresnel diffraction integral in the framework of Rytov theory. This work is concerned with finding a closed-form expression for the average intensity of IGBs propagating through weak and strong Kolmogorov turbulence and completes other scientific research works that deal with numerical approach. The numerical simulations of the analytical average intensity at the receiver plane and the effective beam spot size of the IGBs propagating through turbulent atmosphere environment are presented in this paper. The influences of the beam profile parameters and the turbulence strength on the evolution of the diffracted beam are investigated and discussed. The present results can be a useful tool to predict the behavior of IGBs for the applications in turbulent atmosphere. [ABSTRACT FROM AUTHOR]

The bond-based peridynamics and its extended forms are widely used for crack predicting in many materials like concrete. In peridynamics, as for the bond failure, the tensile failure criterion or tensile-compression failure criterion are commonly applied, the combined tensile-shear or compression-shear failure are rarely considered. In this paper, a Cosserat peridynamic model with a novel bond failure criterion (CPD-BP) is proposed for concrete fracture simulation. The peridynamic bond failure criterion is derived from the Bresler–Pister criterion, with which the composite bond failure can be considered properly. Besides, the Cosserat parameters which relate to microstructures of concrete are introduced. Three benchmarks are designed: simple tensile, direct shear, and compression tests. Results show that the CPD-BP can simulate the combined tensile-shear and compressive-shear concrete failure. Crack patterns predicted by CPD-BP generally follow particle flow code in two dimensions results and physical experiments. The larger Cosserat shear modulus will enhance the shear effects. [ABSTRACT FROM AUTHOR]

In the context of global warming and intensified human activities, glacier instability in plateau regions has increased, and glacier debris flows have become active, which poses a significant threat to the lives and property of people and socioeconomic development. The mass movement process of glacier debris flows is extremely complex, so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement. In view of the interaction between phases in the process of motion, we use the fluid-solid coupling method to describe the mass movement. The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of glacier debris flows and explore their dynamic characteristics. The results indicate that the glacier debris flow lasted for 700 s, and the movement process was roughly divided into four stages, including initiation, scraping, surging and deposition; the depositional characteristics calculated by the fluid-solid coupling model are consistent with the actual survey results and have good reliability; strong erosion occurs during the mass movement, the clear volume amplification effect, and the first wave climbs 17.8 m across the slope. The fluid-solid coupling method can better simulate glacier debris flows in plateau regions, which is helpful for the study of the mechanism and dynamic characteristics of such disasters. [ABSTRACT FROM AUTHOR]

This paper focuses on distributed consensus optimization problems with coupled constraints over time-varying multi-agent networks, where the global objective is the finite sum of all agents' private local objective functions, and decision variables of agents are subject to coupled equality and inequality constraints and a compact convex subset. Each agent exchanges information with its neighbors and processes local data. They cooperate to agree on a consensual decision vector that is an optimal solution to the considered optimization problems. We integrate ideas behind dynamic average consensus and primal-dual methods to develop a distributed algorithm and establish its sublinear convergence rate. In numerical simulations, to illustrate the effectiveness of the proposed algorithm, we compare it with some related methods by the Neyman–Pearson classification problem. [ABSTRACT FROM AUTHOR]

Background: Shortages of mechanical ventilation have become a constant problem in Emergency Departments (EDs), thereby affecting the timely deployment of medical interventions that counteract the severe health complications experienced during respiratory disease seasons. It is then necessary to count on agile and robust methodological approaches predicting the expected demand loads to EDs while supporting the timely allocation of ventilators. In this paper, we propose an integration of Artificial Intelligence (AI) and Discrete-event Simulation (DES) to design effective interventions ensuring the high availability of ventilators for patients needing these devices. Methods: First, we applied Random Forest (RF) to estimate the mechanical ventilation probability of respiratory-affected patients entering the emergency wards. Second, we introduced the RF predictions into a DES model to diagnose the response of EDs in terms of mechanical ventilator availability. Lately, we pretested two different interventions suggested by decision-makers to address the scarcity of this resource. A case study in a European hospital group was used to validate the proposed methodology. Results: The number of patients in the training cohort was 734, while the test group comprised 315. The sensitivity of the AI model was 93.08% (95% confidence interval, [88.46 − 96.26%]), whilst the specificity was 85.45% [77.45 − 91.45%]. On the other hand, the positive and negative predictive values were 91.62% (86.75 − 95.13%) and 87.85% (80.12 − 93.36%). Also, the Receiver Operator Characteristic (ROC) curve plot was 95.00% (89.25 − 100%). Finally, the median waiting time for mechanical ventilation was decreased by 17.48% after implementing a new resource capacity strategy. Conclusions: Combining AI and DES helps healthcare decision-makers to elucidate interventions shortening the waiting times for mechanical ventilators in EDs during respiratory disease epidemics and pandemics. [ABSTRACT FROM AUTHOR]

Multi-frame image super-resolution reconstruction focuses on obtaining a high-resolution (HR) image from a low-resolution image. Since the super-resolution problem is ill-posed, it is frequent to use regularization techniques. However, the choice of these regularization terms is not always direct. Generally, every term should contain some prior knowledge over the image, that is why it plays an important role in increasing the quality of the restored HR image. In this paper, we propose a total variable-order variation based-regularization to provide a natural-looking and an effective reconstruction of the desired HR image. We also present some existence and uniqueness results of our proposed model. The alternating direction method of multipliers algorithm is employed to implement the numerical simulations. Experimental results reveal that the proposed approach can reconstruct and recover high-quality results visually and quantitatively. [ABSTRACT FROM AUTHOR]

The use of grain refiners plays a crucial role in the casting of Al alloys, and ultrasonic treatment is increasingly applied. This paper focuses on the numerical simulations of 2219, an Al–Cu alloy, using different processes for introducing Al–5Ti–1B grain refiner, along with mechanical stirring and ultrasonic treatment. The multiphase Computational Fluid Dynamics (CFD) model considers turbulent fluid flow, heat transfer, solidification, and the complex interaction between the 2219 Al alloy and TiB2 particles. Ansys's fluent dense discrete phase model (DDPM) and a particle engulfment and pushing (PEP) model are utilized for this purpose. The study investigates the fluid flow patterns and the distribution of TiB2 particles. Additionally, four control experiments are designed to correspond with the numerical simulations, enabling the investigation of the variations in α-Al grains and Al2Cu precipitation phases. The findings demonstrate that direct introduction of Al–5Ti–1B into the ultrasonic sonotrode results in uniform dispersion of TiB2 particles in the Al melt, reduction in α-Al grain size, and decreased area fraction of Al2Cu precipitated phase. The numerical simulation results are successfully validated through experimentation. Al–5Ti–1B ultrasonic sonotrode along with ultrasonic treatment has a good effect on 2219 Al alloy. [ABSTRACT FROM AUTHOR]

This paper examines the engineering background of the main shaft of Ruihai Mining Group Company in Laizhou City, with a focus on the loose permeable stratum located in the frozen section of the shaft. Field measurements and data collection, including brine temperature and surface subsidence values, were conducted using temperature and hydrological boreholes. The distribution of the frozen wall temperature field was then numerically simulated using finite element analysis, and the results were compared and analyzed with field data. Scanning electron microscopy (SEM) was used to qualitatively describe the microstructure of the soft rock in the frozen section under different freezing schemes. Based on the formation of the frozen wall, a new construction scheme for freezing and excavating the internal and external circles of the vertical shaft in the loose permeable stratum is proposed. This involves the implementation of "inner and outer double-circles of freezing holes" and a comparison of the freezing effect of the temperature field before and after the improvement. The results indicate that the new freezing scheme can accelerate the freezing rate of the surrounding rock of the shaft, and reduce the time required for closure by more than 10 days. After applying the improved scheme for 60 days, the temperature is lowered by 4–5 ℃ compared to the original scheme, and the thickness of the frozen wall is approximately 4.8 m, significantly thicker than before. These findings demonstrate the effectiveness of adding an inner circle of freezing holes in achieving the lowest temperature which contributes to subsequent shaft excavation. The new scheme holds significant implications for the safe construction of shaft excavation in complex hydrogeological areas. Highlights: The main shaft in the unique geological conditions and the impact of tidal activities on freezing performance are analyzed. The new construction scheme incorporating "inner and outer double-circles of freezing holes" significantly improves freezing efficiency and reduces closure time. The improved scheme results in a thicker frozen wall and lower temperature compared to the original scheme. The findings have important implications for the safe construction of shaft excavation in complex coastal hydrogeological areas. [ABSTRACT FROM AUTHOR]

This paper presents results of development of a numerical model of Lagrangian particle transport, as well as results of application of parallel computation methods to improve the efficiency of the software implementation of this model. The model is a software package that allows the transport and deposition of aerosol particles to be calculated taking into account properties of particles and the input data that describe atmospheric conditions and underlying surface geometry. The dynamic core, physical parameterizations, numerical implementation, and algorithm of the model are described. Results of successful verification of the model on analytical solutions are presented. Initially, the model was used for less computationally intensive problems. In this paper, given the need to use the model in more computationally intensive problems, we optimize the sequential software implementation of the model, as well as develop its software implementations that use parallel computing technologies (OpenMP, MPI, and CUDA). The results of testing different implementations of the model show that the optimization of the most computationally complex blocks in its sequential version can reduce the execution time by 27%. At the same time, the use of parallel computing technologies allows us to achieve acceleration by several orders of magnitude. The use of OpenMP in the dynamic block of the model provides almost 4-fold acceleration of this block; the use of MPI, almost 8-fold acceleration; and the use of CUDA, almost 16-fold acceleration (all other conditions being equal). We also give some recommendations on the choice of a parallel computing technology depending on the properties of a computing system. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of constructing a numerical solution to the system of equations of an acoustic medium in a fixed domain with a boundary. Physically, it corresponds to seismic wave propagation in geological media during seismic exploration of hydrocarbon deposits. The system of first-order partial differential equations under consideration is hyperbolic. Its numerical solution is constructed by applying a grid-characteristic method on an extended spatial stencil. This approach yields a higher order approximation scheme at internal points of the computational domain, but requires a careful construction of the numerical solution near the boundaries. In this paper, an approach that preserves the increased approximation order up to the boundary is proposed. Verification numerical simulations were carried out. [ABSTRACT FROM AUTHOR]

Land subsidence has become a widespread engineering geological problem, which can quickly induce many derived disasters. Over-exploitation of groundwater is one of the main factors of urban land subsidence. There is severe land subsidence in Jining, mainly induced by groundwater over-extraction. Therefore, the numerical simulation method is used in this paper to analyze and predict the law of land subsidence in Jining. Combined with the engineering geological and hydrogeological conditions of Jining City, a three-dimensional fluid–solid coupling model of land subsidence was established by using COMSOL software. The numerical results were verified using site monitoring data. The article predicts the land subsidence in the study area in 2030. In 2030, the maximum land subsidence is 224 mm. And this paper analyzes the land subsidence pattern under different groundwater extraction amounts. The results show that the land subsidence in the study area is effectively alleviated under the condition of reducing water extraction by 30%. It provides a basis for preventing and controlling land subsidence in Jining city. It is proved that land subsidence caused by groundwater extraction positively correlates with the pumping time and amount of water pumped. [ABSTRACT FROM AUTHOR]

This article presents and investigates a modified version of the Weibull distribution that incorporates four parameters and can effectively represent a hazard rate function with a shape resembling a bathtub. Its significance in the fields of lifetime and reliability stems from its ability to model both increasing and decreasing failure rates. The proposed distribution encompasses several well-known models such as the Weibull, extreme value, exponentiated Weibull, generalized Rayleigh, and modified Weibull distributions. The paper derives key mathematical statistics of the proposed distribution, including the quantile function, moments, moment-generating function, and order statistics density. Various mathematical properties of the proposed model are established, and the unknown parameters of the distribution are estimated using different estimation techniques. Furthermore, the effectiveness of these estimators is assessed through numerical simulation studies. Finally, the paper applies the new model and compares it with various existing distributions by analyzing two real-life time data sets. [ABSTRACT FROM AUTHOR]

In this paper, a novel distributed adaptive neurodynamic approach (DANA) based on proportional integral technique is proposed to solve distributed optimization problem on multi-agent systems. The goal is that all agents reach consensus in finite time and converge to the optimal solution of the global objective function in fixed time. In the proposed approach, the proportional technique drives all agents to reach consensus, and the integral technique is used to offset the influence of the gradient term of the objective function. On the other hand, in order to avoid the prior estimation of gain parameter and the global gradient information, as the main contribution of this paper, the adaptive idea is considered into proportional integral technique. The results show that the adaptive integral technique can automatically adjust the gain according to the maximum consensus error between agents, so as to ensure that agents can achieve consensus in finite time. Then the theoretical results are applied to voltage distribution and logistic regression. Numerical simulation verifies the effectiveness of DANA. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this paper is to re-visit the design of three steps in the freeze-drying process, namely freezing, primary drying, and secondary drying steps. Specifically, up-to-date recommendations for selecting freeze-drying conditions are provided based on the physical–chemical properties of formulations and engineering considerations. Methods and Results: This paper discusses the fundamental factors to consider when selecting freezing, primary drying, and secondary drying conditions, and offers mathematical models for predicting the duration of each segment and product temperature during primary drying. Three simple heat/mass transfer primary drying (PD) models were tested, and their ability to predict product temperature and sublimation time showed good agreement. The PD models were validated based on the experimental data and utilized to tabulate the primary drying conditions for common pharmaceutical formulations, including amorphous and partially crystalline products. Examples of calculated drying cycles, including all steps, for typical amorphous and crystalline formulations are provided. Conclusions: The authors revisited advice from a seminal paper by Tang and Pikal (Pharm Res. 21(2):191-200, 2004) on selecting freeze-drying process conditions and found that the majority of recommendations are still applicable today. There have been a number of advancements, including methods to promote ice nucleation and computer modeling for all steps of freeze-drying process. The authors created a database for primary drying and provided examples of complete freeze-drying cycles design. The paper may supplement the knowledge of scientists and formulators and serve as a user-friendly tool for quickly estimating the design space. [ABSTRACT FROM AUTHOR]

As cities have grown, conductor rail power supplies have been widely used in the field of urban rail transit. In order to improve the running performance of trains and reduce the occurrence of accidents, it is necessary to understand the vibration of shoegear-rail system under different initial contact forces and explore the dynamic performance of shoegear-rail system. Therefore, according to the structure of shoegear-rail system, a coupling model of shoegear-rail system is established in this paper. On the basis of the model, the numerical simulation of the shoegear-rail system under different initial contact forces is carried out, and finally the vibration data of the shoegear-rail system under different initial contact forces are obtained. The results show that with the increase of initial contact force in the range of 70–160 N, the vibration amplitude of the electric shoegear and the fluctuation amplitude of the contact force increase, but the maximum absolute shear force value of the conductor rail decreases. It indicates that the lower initial contact force, the better the performance of shoegear-rail system. [ABSTRACT FROM AUTHOR]

The paper proposes an approach to the numerical stochastic modeling of the time series of the wind chill index and equivalent effective temperature at weather stations located in the Arctic zone of the Russian Federation. The approach is based on the use of a specially designed stochastic weather generator. It is shown that the approach allows developing the models of the time series of bioclimatic indices that very accurately reproduce various statistical properties of real processes related, in particular, to their daily variations and specific features of the study area. [ABSTRACT FROM AUTHOR]

The derivation of pseudorandom number generation (PRNG) from the Josephson junction (JJ) stimulated by the Wien bridge oscillator (JJSWBO) and its microcontroller validation is given in this paper. Via the numerical investigations of the JJSWBO, the encyclopedic dynamical maps in different coordinate spaces constituting the system's parameters explicitly elaborate the global behaviour of the system presenting the greatest Lyapunov exponents (GLE). Chaotic behaviours were captured for GLE greater than zero and periodic behaviours for GLE less than zero. Further, bifurcation characteristics expose monostable and bistable periodic oscillations, bistable periodic doubling route to bistable chaos, interceptions of bistable regular behaviours and bistable chaotic presentations, coexisting attractors, monostable chaotic dynamics and intermittency phenomenon. The microcontroller validation (MCV) of the JJSWBO is presented to validate the numerical simulation results. From the chaotic equations describing JJSWBO, a PRNG with a linear feedback shift register (LFSR) as a post-processing unit is designed. The randomness of the generated binary data from the proposed JJSWBO-based PRNG is successfully tested by using the NIST 800-22 test suite. This result helps to confirm the suitability of the JJSWBO for encryption schemes and other chaos-based applications. [ABSTRACT FROM AUTHOR]

With the increasing demand for household appliances, people are putting forward higher requirements for their sound quality. In this paper, we apply the theory of acoustic metamaterials to a bladeless fan and propose a curly space-type acoustic metamaterial (CSAM) to optimize the sound quality while ensuring the airflow of the bladeless fan. The acoustic transmission loss of CSAM is calculated by numerical simulations. Based on the hybrid approach to calculating aerodynamic acoustics (CAA) to calculate the aerodynamic noise of the bladeless fan, the ICFD module of Actran is used to convert the CFD simulated data into sound field data. The internal flow field and sound field of the bladeless fan with or without CSAM are compared and analyzed. Finally, an experimental test is done to verify the noise reduction effect and air velocity change after adding CSAM. The analysis shows that the change in the air velocity of the bladeless fan by adding CSAM is not apparent, and the sound pressure level at the monitoring point is reduced. The experimental results show that the noise of the bladeless fan is reduced by 4.9 dB after adding CSAM, and the wind speed at the location of the monitoring point is increased by 0.08 m/s. Without affecting the air velocity, CSAM can change the intensity of the sound source inside the bladeless fan and effectively suppress the aerodynamic noise. It demonstrates the feasibility of acoustic metamaterials to reduce aerodynamic noise. [ABSTRACT FROM AUTHOR]

In this paper, a sub-wavelength sector acoustic metamaterial (SAM) cell was presented for duct noise attenuation. A numerical model considering thermal-viscous loss was established to quantitatively reveal the influence of different structure parameters on the effective bandwidth and peak frequency. Findings clarify that thermal dissipation occurs mainly in the cavity and viscous dissipation exists mainly in the channel. The negative effective bulk modulus for SAM was calculated by the parametric retrieving method. A developed sector acoustic metamaterial (DSAM) structure was proposed by periodically configuring the SAM. The corresponding numerical model was established, and the effective bandwidth of DSAM was calculated. Results demonstrate that the DSAM has sufficient bandwidth to ensure noise attenuation. The experiments were conducted using the quadrupole method acoustic test system under dual-load conditions. The error of the STL curve peak frequency for the SAM cell compared with the numerical calculation was 0.51 %, and the error of the effective bandwidth was 1.4 %, which verified the accuracy of the numerical model. This study serves as an essential catalyst for applying acoustic metamaterial in the field of duct noise attenuation. [ABSTRACT FROM AUTHOR]

This paper presents a solution for the security of few-detail images in real-time applications over open or unsecure networks depending on diffusion and confusion operations. The diffusion and confusion operations are both performed based on Henon and Baker chaotic maps. XOR and permutation operations are used to allow diffusion and confusion in the algorithm. In the proposed algorithm, a high-detail image is used as a key. The computer simulation results and security analysis are given to ensure the validity and strength of the proposed algorithm. In the security analysis, we have performed key-space analysis, cropping attack analysis, noise attack analysis, and differential attack analysis. Some statistical analyses based on entropy, histogram, and correlation coefficient estimation are also given to check the strength of the presented algorithm. [ABSTRACT FROM AUTHOR]

The freezing damage of rock tunnels in cold region involves ice-water phase change and complicated interaction of Thermo–Hydro–Mechanical (THM) field. Taking the fractured rock mass of cold region tunnels as research subject, the THM coupling model of cold region tunnels was established, which is based on the seepage mechanics, heat transfer theory, damage mechanics and equivalent continuum theory. This model could reflect the anisotropic properties of deformation, water migration and heat transfer caused by the initial fracture of rock mass. The construction and operation processes of a rock tunnel in cold region were simulated, and results were compared with the measured value and predecessor's achievements. It shows that proposed model could reflect the anisotropic property of surrounding rock and the simulated deformation and stress are not symmetrical. Compared with the literature, the calculated results in this paper are closer to the measured values. The insulating layer has a significant effect on the stress of the supporting structures. The maximum tension stress of the lining is 4.5 times as that without insulating layer, and the lining will be destroyed for the overlarge tension stress. [ABSTRACT FROM AUTHOR]

Equation-free modeling aims at extracting low-dimensional macroscopic dynamics from complex high-dimensional systems that govern the evolution of microscopic states. This algorithm relies on lifting and restriction operators that map macroscopic states to microscopic states and vice versa. Combined with simulations of the microscopic state, this algorithm can be used to apply Newton solvers to the implicitly defined low-dimensional macroscopic system or solve it more efficiently using direct numerical simulations. The key challenge is the construction of the lifting and restrictions operators that usually require a priori insight into the underlying application. In this paper, we design an application-independent algorithm that uses diffusion maps to construct these operators from simulation data. Code is available at https://doi.org/10.5281/zenodo.5793299. [ABSTRACT FROM AUTHOR]

In this paper, an optimal nonlinear attitude controller is designed and implemented as hardware in the loop for a spacecraft simulator under various failures of reaction wheels. The proposed controller is developed in the closed form based on predicting the nonlinear continuous responses of spacecraft simulator. The special case of the controller when all uncertainties are ignored leads to feedback linearization. However, the stability of the controller in the presence of parametric uncertainties and unmodeled dynamics of the platform is analyzed, and the effect of the prediction time on the boundedness of system responses is presented. A redundant reaction wheel is located in the platform to compensate for failures of three main reaction wheels. How to distribute torque between healthy wheels under different types of failure including stuck and oscillatory failures is addressed and experimentally implemented. The laboratory results that are consistent with computer simulations show the accuracy and validity of the designed controller. It is seen that the spacecraft attitude converges in a limited time in the presence of system uncertainties and actuator failures. [ABSTRACT FROM AUTHOR]

Transformerless grid-connected inverters for photovoltaic (PV) applications provide several advantages such as reduced cost and volume as well as an increased efficiency. However, the removal of the transformer gives rise to several problems related to leakage currents and electromagnetic interferences (EMI). This paper presents different chaotic unipolar sine-pulse width modulation (C-USPWM) techniques for a transformerless grid-connected PV inverter based on parameter selection. The main objective behind this proposed chaotic modulation technique is to reduce the conducted EMI without worsening the power quality and the common-mode voltage (CMV). The method is validated through numerical simulations and experimental tests carried out on laboratory prototype of an optimized H5 inverter (oH5). The obtained results showed its superiority to the conventional unipolar sine-pulse width modulation (USPWM). We showed also that the appropriate parameter selection of the C-UPSWM could advantageously combine an improved EMI performance and an efficient control, making it possible to deliver a significant reduction of the peaks' amplitudes in the frequency spectrum of the common-mode (CM) voltage. [ABSTRACT FROM AUTHOR]

3D Concrete Printing (3DCP) is a rapidly evolving technology that allows for the efficient and accurate construction of complex concrete objects. In this paper, a numerical modelling approach is presented for the simulation of the printing process of cementitious materials, based on the homogeneous fluid assumption. To cope with the large deformations of the domain and the nonlinearity resulting from the use of a non-Newtonian rheological law, the Navier–Stokes equations are solved in the framework of the Particle Finite Element Method (PFEM). Furthermore, tailored solutions have been formulated and implemented for the time-dependent moving boundary conditions at the nozzle outlet and for the efficient handling of the inter-layer contact in the same PFEM framework. The overall computational cost is decreased by the implementation of an adaptive de-refinement technique, which drastically reduces the number of degrees of freedom in time. The proposed modelling approach is finally validated by simulating the printing process of six rectilinear layers and one multi-layer "wall". The results show good agreement with the experimental data and provide valuable insights into the printing process, paving the way for the use of numerical modelling tools for the optimization of materials and processes in the field of 3D Concrete Printing. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) system features with integrated high-pressure urea dosing pump to regulate the urea spray injection pressure for pertinent mixing of evaporated ammonia with exhaust gas mixtures in the diesel engine. This paper is a contribution to numerical simulation studies of external gear pumps using the immersed solid method for better understanding of continuously changing fluid fields and transient flow characteristics. A comprehensive set of data gained by the investigations from KATECH institute was executed in the present study, which led to an optimized CFD setup for realistic numerical simulation. Parametric analyses have been carried out for the gear speed and supplied urea liquid mass flow rate to find the behavior of pressure, mass flow rate, and velocity fluctuations in the domain. As a result, the pressure at the outlet reached its maximum with the increase in rotational speed, and the fluctuations grew. [ABSTRACT FROM AUTHOR]

Fabrizio and Caputo suggested an extraordinary definition of fractional derivative, which has been used in many fields. The SIDARTHE infectious disease model with regard to COVID-19 is studied by the new notion in this paper. Making use of the Banach fixed point theorem, the existence and uniqueness of the model's solution are demonstrated. Then, an efficient method is utilized to deduce the iterative scheme. Finally, some numerical simulations of the model under various fractional orders and parameters are shown. From the computed result, we can see that it not only supports the theoretical demonstration, but also has an intensive insight into the characteristics of the model. [ABSTRACT FROM AUTHOR]

Zirconia ceramics have become a reliable material for mechanical components, such as plungers. This paper aimed to optimize bionic texture parameters to enhance the tribological properties of these components. We extracted profiles from fish scales and ant abdomens, then conducted numerical simulations and experiments to study the anti-friction properties of textured surfaces. Results showed that scale textures have a greater lubricant film carrying capacity and a wider positive pressure distribution than other types. Smaller texture depths had a higher energy conversion rate. Optimal area occupancy allowed for adequate secondary lubrication and the best anti-friction performance. Texture depth, shape, and area occupancy all affected the friction coefficient of zirconia ceramic samples. The sample with a scaled texture pattern had the best friction reduction with a texture depth of 20 μ m and 10% area occupancy under light load, and 60 μ m and 10% area occupancy under medium to heavy load. The numerical simulations and experimental results supported each other, providing theoretical guidance for optimal bionic texture parameter design under various application conditions. [ABSTRACT FROM AUTHOR]