Search

Due to increasing air pollution, which is a consequence of the environmental effects of production in various industries, green supply chain management (GSCM) has attracted the attention of both scholars and practitioners. Green supplier selection is an important problem in GSCM and seeks to satisfy a firm's environmental goals as well as its economic targets. In this paper, for the first time, a green supplier selection problem considering both green and non-green evaluation criteria in a closed-loop supply chain is studied, and a cap-and-trade mechanism as a way of controlling the air pollution caused by manufacturers is proposed. To solve this particular problem, we propose a multi-objective robust optimization (RO) model. This specific model is an effective approach to handle uncertainty. A numerical example using randomly generated data, accompanied by subsequent discussion of the proposed approach, is deployed to validate the model. The results prove that the developed model for green supplier selection is able to effectively enhance the decision-making process of the experts. By illustrating the trade-off in robustness between the model and proposed solutions, as well as the effect of the deviation penalty on the closeness of results to the achieved solution, we show how firms can make optimal decisions when assigning the parameters. Furthermore, analyses show that decreasing the allowance amount (cap) and increasing the allowance prices in the cap-and-trade system escalate the firms' costs, but lower the amount of carbon released. Finally, we show that the cap-and-trade mechanism results in a better solution in terms of the total utility of the supply chain compared to the penalty-based system for a specific range of carbon allowance. • This paper generalizes the green supplier selection and order allocation problem. • A mathematical model for the problem is developed. • A robust optimization approach to handle the model uncertainty is developed. • The impact of changes in model parameters on the objective functions is analyzed. • The cap-and-trade mechanism is compared with a penalty-based mechanism. [ABSTRACT FROM AUTHOR]

This paper presents a model to simulate behavior of particle-laden slurry in a horizontal perforated wellbore with the goal of quantifying fluid and particle distribution between the perforations. There are two primary phenomena that influence the result. The first one is the non-uniform particle distribution within the wellbore's cross-section and how it changes along the flow. The second phenomenon is related to the ability of particles to turn from the wellbore to a perforation. Consequently, the paper considers both of these phenomena independently at first, and then they are combined to address the whole problem of flow in a perforated wellbore. A mathematical model for calculating the particle and velocity profiles within the wellbore is developed. The model is calibrated against available laboratory data for various flow velocities, particle diameters, pipe diameters, and particle volume fractions. It predicts a steady-state solution for the particle and velocity profiles, as well as it captures the transition in time from a given state to the steady-state solution. The key dimensionless parameter that quantifies the latter solution is identified and is called dimensionless gravity. When it is small, the particles are fully suspended and the solution is uniform. At the same time, when the aforementioned parameter is large, then the solution is strongly non-uniform and resembles a flowing bed state. A mathematical model for the problem of particle turning is developed and is calibrated against available experimental and computational data. The key parameter affecting the result is called turning efficiency. When the efficiency is close to one, then most of the particles that follow the fluid streamlines going into the perforation are able enter the hole. At the same time, zero efficiency corresponds to the case of no particles entering the perforation. Solutions for the both sub-problems are combined to develop a model for the perforated wellbore. Results are compared (not calibrated) to a series of laboratory and field scale experiments for perforated wellbores. Comparison with the available computational results is presented as well. In addition, the comparison is presented in view of the parametric space defined by the dimensionless gravity and turning efficiency. Such a description allows to explain seemingly contradictory results observed in different tests and also allows to highlight parameters for which perforation orientation plays a significant role. • A model for particle dynamics in a perforated pipe is developed. • Solution for particle distribution in a turbulent slurry flow is constructed. • Higher particle concentration is predicted at the bottom of the pipe. • The problem of particles missing the perforation is solved. • The developments are validated against numerous experimental observations. [ABSTRACT FROM AUTHOR]

The occurrence of dynamic events such as machine breakdown during workshop production can make the original scheduling scheme infeasible. Therefore, this paper establishes a mathematical model for a multi-objective dynamic flexible job shop scheduling problem with machine breakdown, and proposes a multi-objective migrating birds optimization algorithm based on game theory. Firstly, in order to solve the problem of difficult to determine the weight in weighted multi-objective optimization, this paper introduces game theory to balance the Pareto optimality and fairness between the two objectives of production efficiency and stability. When solving the solution of the game model, there may be no perfect Nash equilibrium solution, so a solution method that approximates the Nash equilibrium solution is designed. In the improved migrating algorithm, neighborhood operators based on path relinking and machine age are designed to improve the search ability. Based on the attributes of multi-objective problems, a multiple similarity measure method is designed to select and replace solutions. The experiment part proves the effectiveness of the game strategy in multi-objective optimality and fairness, and concludes that the algorithm has good performance by comparing with the advanced algorithms in recent years. • A multi-objective game model is designed to solve dynamic scheduling problems. • The approximate Nash equilibrium solution is designed to solve the game matrix. • The neighborhood operators of path relinking and machine age are designed. • A multiple similarity measurement method is designed for multi-objective problem. [ABSTRACT FROM AUTHOR]

• A mathematical methodology to find the optimal NIR light protocol in transdermal drug delivery; • Strategy based on an optimization problem minimizing the difference between target and simulated drug absorption profile; • The optimization problem relies on a 2D mathematical model for NIR light controlled transdermal drug delivery; • Validation of the transdermal model against laboratory data; • Convergence and stability analysis of a finite difference spatial scheme for a generalization of the transdermal model. Near-infrared light-controlled transdermal drug delivery (NIRTDD) has several advantages over traditional delivery methods, and it is now undergoing extensive research. One prominent aspect of NIRTDD is the possibility of keeping the drug concentration in its optimal therapeutic window using a suitable near-infrared light protocol. The problem is that this ideal protocol is usually unknown. In this paper, we propose a computational tool that aims at solving this issue. The computational tool relies on an optimization problem involving the numerical simulation of a two-dimensional mathematical model for NIRTDD. We also analyze the convergence and stability of a finite difference spatial scheme for a generalized version of this mathematical model. [ABSTRACT FROM AUTHOR]

Ducts are conduits or passages used to supply, return, or exhaust air, needed for heating, ventilation, or air conditioning in multistory gigantic building structures. Rapid growth in population (especially in industrially concentrated regions) has led to the culture of constructing skyscrapers of tens of storeys, in which vertical ducts are the natural choice for removing polluted air. Due to the compactness of the building design, high voltage current-carrying wires are usually located very close to exhaust ducts carrying polluted air. Consequently, a natural motivation is to study how the magnetic field produced by such a wire affects the flow, driven by an external pressure gradient (for example, exhaust fan, vacuum pump, etc.) in a vertical duct. Therefore, the paper is devoted to understanding the interaction of the developed (thermally and hydrodynamically) flow in a vertical square duct with the magnetic field produced by a nearby placed current-carrying wire. The flow is assumed to be laminar and is driven by a constant external pressure gradient. For the thermal boundary condition, we assume a uniform heat flux across the unit axial length whereas a fixed temperature is also assumed over the peripheral surface of the duct. As a result of the mathematical modeling of the problem, we come across a system of coupled Poisson-like equations which are solved numerically by following a finite volume approach. We have noted that a sufficiently higher Rayleigh number may cause a reverse flow while reducing and flattening the thermal distribution in the middle of the duct. In addition the magnetic field further reduces the flow velocity, particularly near the duct wall where the current-carrying wire (causing the magnetic field) is positioned. [ABSTRACT FROM AUTHOR]

• An industrial cargo routing problem with split loads motivated from a major steel company is studied. • Cargo-cargo and cargo-ship compatibility and the minimum loading amount for using a ship are considered. • An efficient path flow-based mathematical model is proposed. • The proposed model can reduce the computation time by 67% compared to an arc flow model. This paper presents an industrial ship routing problem with split loads faced by a steel company that exports its steel products to neighboring countries. The problem considers two types of ships: ships with contracts of affreightment and spot ships. It also considers other practical constraints, such as cargo–cargo and cargo–ship compatibility and the minimum loading amount for using a ship. Due to high surcharges for multiple port visits, each ship is allowed to visit at most two loading and two unloading ports. Herein, arc flow-based and path flow-based mathematical models are proposed to solve the problem. Computational experiments show that the path flow model is more efficient than the arc flow model. The path flow model can reduce the computational time by 67% on average and find optimal solutions to real-world ship routing problems in acceptable computational time in most cases. [ABSTRACT FROM AUTHOR]

• Addressing complexity in energy transition with mathematical models. • Interpretable ML for understanding power system solutions. • Compact descriptions of optimal commitment solutions. • Extracting insights from experiential knowledge with ML. The energy transition needs mathematical models to address the complexity of shifting towards sustainable energy sources. In addition to providing accurate solutions, these models must be explainable and available for discussion among stakeholders to facilitate informed decision-making and ensure a successful transition. This paper contributes to the explainability of power systems models by applying interpretable machine learning techniques to improve understanding of the solutions to the unit commitment problem. It applies them to a case study based on the IEEE 118N system. The developed methodology aims at describing the optimal commitment solutions as a function of the conditions of the system in a compact manner that is understandable by a human being. This type of information takes the form of 'which plants are needed under which conditions' and is routinely learned by experience by system operators and other agents participating in the system. This experiential knowledge is realized in an approximate form that is simple enough to help make or justify decisions. By applying interpretable machine learning techniques, our methodology can automatically extract what was previously only available through human experience and reflection. Our approach involves model trees and node clustering to find a concise description of the different situations where the system can be found. Our results show that the methodology can explain these modes of operation for the 118N system in a sufficiently simple manner to be understood by a human unfamiliar with the system. This shows that interpretable machine learning can provide valuable insights into real solutions of the unit commitment and help improve decision-making in this area. [ABSTRACT FROM AUTHOR]

• A micro-capillary jetting technology, broadening the boundary of microchannels, is proposed. • It can produce microdroplet controllably at high Q d without the restriction of phase ratio. • The laws of the micro-capillary jetting technology is systematical reported. • A quantitative model to distinguish three jetting patterns is provided for the first time. • A predicted model for droplet size and the energy utilization during jetting is established. Liquid-liquid microdispersion is one of the key foundations for chemical process intensification. However, liquid-liquid microdispersion at the conditions of high phase ratio and high volume flow rate remains a problem and new microdispersion technology is highly required. Based on the microscale effect of the liquid jet, we developed the micro-capillary jetting technology. It can produce microdroplets (250–500 μm) with narrow size distribution (CV ≈ 10–20 %) in a wide range of physical properties with large capacity and little cost without the restriction of phase ratio. This paper reports the laws of the micro-capillary jetting technology. The liquid-liquid flow patterns and mechanism are studied, and a precise quantitative model to distinguish different jetting patterns is provided for the first time based on the energy analysis in the microscale. Then important factors including physical properties, dispersion mode and structural parameters are investigated. Accordingly, a mathematical model for the prediction of the average droplet size is established and the energy utilization in the jetting dispersion process is calculated. [ABSTRACT FROM AUTHOR]

• A new nonlinear fatigue damage constrained topology optimization (NFDCTO) is presented. • Topology optimization formula and framework considering nonlinear fatigue damage are presented. • Morrow's plastic work interaction rule is used to calculate the nonlinear cumulative damage of the structure. • The superiority of the NFDCTO method is presented by comparing to the traditional linear fatigue damage methods. • The NFDCTO method is effective and feasible in addressing fatigue optimization challenges for 3D structures. In engineering applications, plenty of components are subjected to variable-amplitude cyclic loading, resulting in fatigue damage, which is one of the main forms of structural damage. While the linear damage rule has long served as a fundamental approach, its limitations necessitate advancements for more accurate fatigue life predictions. Hence, this paper introduces a pioneering method termed nonlinear fatigue damage constrained topology optimization (NFDCTO). This method integrates several key components: the rainflow counting method to evaluate the non-proportional cyclic load levels, Basquin's equation to describe the S-N curve, and Morrow's plastic work interaction rule to calculate the nonlinear cumulative damage of the structure. Consequently, we establish a mathematical model for the NFDCTO method based on these components. The incorporation of penalized damage aggregation with the P-Normal function is used to address significant constraints and singularity challenges. Furthermore, by employing the adjoint method, we derive sensitivity equations for both the objective function and fatigue constraint function concerning the design variables. Subsequently, the superiority of the NFDCTO method over traditional linear fatigue damage method were verified applying 2D l -shaped beam and simply supported structures as examples. Concurrently, bridge structures were employed to investigate the effect of the sensitivity index of the material to the history of variable amplitude stresses on the optimization results. In addition, the influence of the fatigue penalty factor on the topology optimization results was assessed using a 2D cantilever beam. Finaly, we verify the effectiveness and feasibility of the NFDCTO method in addressing fatigue optimization challenges for 3D structures utilizing two 3D examples. [ABSTRACT FROM AUTHOR]

To drive a paradigm shift towards a human-centric approach in remanufacturing systems and promote energy-efficient, carbon-reduction-friendly upgrades, this paper introduces a stochastic human–robot collaborative disassembly line balancing problem for real-world disassembly lines characterized by uncertain operation times. The developed mathematical model takes into account task priority relationships, task attributes, human–robot collaboration, and cycle time constraints, with the goal of optimizing workstation numbers, smoothing indices, and carbon emissions. Subsequently, we propose a hybrid evolutionary algorithm (HEA) to efficiently address this problem. The algorithm includes methods for generating initial solutions and decoding them based on random disassembly time. Additionally, an enhanced differential evolution operation is integrated into the non-dominated sorting genetic algorithm II (NSGA-II) framework to improve the algorithm's evolutionary and search capabilities. Validation experiments involving 21 benchmark cases demonstrate that HEA significantly outperforms seven other algorithms reported in the existing literature. Finally, the proposed algorithm is applied to a printer case comprising 55 components. The results underscore the algorithm's superior search capabilities compared to the innovative hybrid algorithm, genetic simulated annealing algorithm, as well as traditional NSGA-II and evolutionary algorithms, under both low and high randomness conditions. • The carbon emission evaluation index was developed for HRC-DLBP. • Incorporating product- and operator-induced uncertainty into HRC-DLBP. • Developed a multi-objective hybrid evolutionary algorithm for SHRC-DLBP. • Apply the proposed method to the discarded printer disassembly case. [ABSTRACT FROM AUTHOR]

In ultra-precision combined grinding, the spindle deformation caused by the grinding force and wheel gravity influences the actual grinding depth, leading to the machining accuracy of the cylindrical microlens array (CMA) molds. In this paper, a mathematical model of spindle deformation is established based on spindle stiffness and grinding force. The single-grain trajectory is set up on account of the mathematical model. The surface data of the wheels are collected, and the grains protrusion height of the wheels is reconstructed using the Johnson conversion. The morphology of the molds is simulated considering the elastic displacement deformation of the spindle. The combined grinding experiments were conducted to verify the theoretical model through the surface topography. The results show that the combined grinding strategy has little effect on the surface accuracy of the CMA molds. It was found that combined grinding improves grinding efficiency and meets surface accuracy requirements. • A mathematical model considering spindle deformation on combined grinding was established. • The simulation profile has a high degree of consistency with the experimental profile. • Combined grinding strategy can improve machine efficiency and meet the accuracy requirements. • Different material removal mechanisms appeared in the rough-fine combined grinding process. [ABSTRACT FROM AUTHOR]

• Intersection discretization issues resolved using a combination of ordinary and massless beams. • Bending-torsional hybrid equations for diverse beams are established by introducing total bending angle to the state vector. • Established three transfer conditions to solve the complex connection problem of cross-type beams. • Proposed modeling method predicts the electromechanical characteristics more accurately than FEM. Cross-type piezoelectric beams (CTPBs) have been widely employed in the fields of transducers, actuators, sensors, energy harvesters, and vibration control due to their unique vibration form. However, there is still a lack of electromechanical-coupling dynamic model for describing the two-dimensional out-of-plane bending vibration of CTPBs. The main reason is that the current mathematical modeling methods cannot accurately couple the dynamical parameters of beam vibrations in both directions. To solve this problem, a novel modeling method based on the transfer matrix method (TMM) is proposed in this paper. Initially, a new discretization concept is created to discretize the intersection of CTPBs into ordinary and massless elastic beams. Subsequently, the bending-torsional hybrid vibration transfer equations for discrete sub-elements are established. Finally, by deriving the two-dimensional transfer conditions of discrete sub-elements and combining the transfer equations, an electromechanical-coupling dynamic model of CTPBs is developed. In this study, the proposed modeling method is used to establish the electromechanical-coupling dynamic models of odd- and even-order out-of-plane bending vibrations of cross beams as case studies. And the validity of the models is verified through both finite element method and experimental study. Moreover, comparison results indicate that the established models can predict the impedance characteristics of the vibrators more accurately than finite element methods. The proposed modeling method fills the gap of the semi-analytical method in analyzing the two-dimensional out-of-plane vibration characteristics of CTPBs. [Display omitted] [ABSTRACT FROM AUTHOR]

Classical methods of medical image super-resolution (MISR) utilize open-loop architecture with implicit under-resolution (UR) unit and explicit super-resolution (SR) unit. The UR unit can always be given, assumed, or estimated, while the SR unit is elaborately designed according to various SR algorithms. The closed-loop feedback mechanism is widely employed in current MISR approaches and can efficiently improve their performance. The feedback mechanism may be divided into two categories: local feedback and global feedback. Therefore, this paper proposes a global feedback-based closed-cycle framework, circular MISR (CMISR), with unambiguous UR and advanced SR elements. Mathematical model and closed-loop equation of CMISR are built. Mathematical proof with Taylor-series approximation indicates that CMISR has zero recovery error in steady-state. In addition, CMISR holds plug-and-play characteristic that fuses model-based and learning-based approaches and can be established on any existing MISR algorithms. Five CMISR algorithms are respectively proposed based on the state-of-the-art open-loop MISR algorithms. Experimental results with three scale factors and on three open medical image datasets show that CMISR is superior to MISR in reconstruction performance and is particularly suited to medical images with strong edges or intense contrast. [ABSTRACT FROM AUTHOR]

Established model-based methods often use a combination of state feedback and observer to control complex systems. They rely on detailed mathematical models that are often hard to derive. Nonetheless, such methods may achieve a high level of accuracy, which justifies the cumbersome modelling. An alternative approach is model-free control, in a form introduced by Fliess and Join, where the system is approximated in a short time interval by a low-order differential equation with unknown parts, a so-called ultra-local model. This control method is a powerful tool, but the parametrisation and the concrete implementation may require time, effort, and experience. The present paper investigates the systematic tuning of a model-free controller for a magnetically supported plate that is modelled as an unstable multiple-input multiple-output system. Furthermore, the incorporation of model information into the model-free controller is investigated. These adaptations ultimately improve results by simplifying parameter tuning and interpretation of estimates. Several experiments are carried out on a test bed to show the capabilities of the proposed algorithms for set point stabilisation and trajectory tracking. The effects of the different parameters in the model-free controllers are addressed, and excellent robustness with respect to actuator faults is demonstrated. Filters for estimating derivatives and unknown quantities are designed using an open-source toolbox. [Display omitted] • Model-free control with experimental validation. • Model-free control of an overactuated multiple-input multiple-output system. • Parametrisation of model-free controllers for second order ultra-local models. • Comparison of model-based and model-free control. [ABSTRACT FROM AUTHOR]

The development of accurate and reliable mathematical models is the cornerstone for the modeling and optimization of processes. However, most of the existing models suffer from weak prediction capabilities due to poor data information content and poor parameter estimation methodologies. Several estimability approaches have been developed and increasingly implemented to address some of these issues. However, the wider adoption of these methods is still hampered by the lack of standardized and robust methodologies. In this paper, we present a Matlab Toolbox, called ESTAN, designed and developed to make estimability analysis accessible to non-specialist users. It uses a Quasi-Monte Carlo sequence to sample the main unknown parameters within their variation spaces. Then, depending on whether the studied model is computationally cheap or expensive, sensitivity indices are calculated either using the Sobol method or Fourier Amplitude Sensitivity Test (FAST). The calculated sensitivities are finally used within an orthogonalization algorithm to rank the parameters from the most to less estimable ones and to determine the estimable and non-estimable ones based on an estimability cut-off criterion. Various case studies are used to validate the toolbox and guide the users. The first one deals with the non-dynamic Toth adsorption model, while the second one deals with a dynamic batch cooling crystallization model. The main challenge with these two case studies is to show the importance of estimability analysis in the interpolation/extrapolation of model prediction capabilities. The last case addresses a computationally expensive thermodynamic model. The results for all the case studies are found to be promising, showing how the presented toolbox simplifies the investigation of the estimability analysis. [Display omitted] • A new global sensitivity-based estimability analysis Toolbox is proposed. • The toolbox ESTAN is validated based on three different mathematical models. • Model prediction capabilities are enhanced based on both interpolation and extrapolation. • ESTAN allows cost effective computations of the global sensitivities by switching from SOBOL to FAST. • ESTAN is an open-source package dedicated to non-commercial research. [ABSTRACT FROM AUTHOR]

This paper presents an offline optimization method designed for use with industrial robots in environments with static obstacles. It is particularly useful in industry where stability and predictability are crucial to meeting expected timelines in automated guided vehicle operations. The main methodological contribution of this work lies in the integral process used to define an effective fitness function that guides the optimization method in the search for optimal solutions. This cost function plays a critical role in the effectiveness of the trajectory tracking algorithm by quantifying path quality and allowing comparisons between solutions. The design of this fitness function poses challenges including accuracy, suitability, minimization of path length, and avoiding or reducing collisions. To achieve the optimization objectives and address some issues such as sensitivity to parameter scaling and the risk of premature convergence, different approaches can be used. This work proposes to incorporate constraints into the fitness function, adjust the optimization parameters to reflect the conditions of the problem, and design a fitness function based on prior knowledge and an accurate representation of the goals. The three relevant contributions for the planning and optimization of routes of automated guided vehicle in industrial environments are the following. Firstly, the development of a mathematical model of trajectories based on Frenet curves that considers the static occupancy map of the environment. Second, an optimization strategy to generate optimal safe paths. Finally, a fitness function that guides the optimization method towards optimal solutions considering the sensitivity to scaling and resolution of the parameters. This study presents an exhaustive analysis of the different fitness functions obtained, each one evaluated based on key metrics such as the length of the trajectory, the average and minimum distance to the occupancy map, and the number of collisions along the path. The results show that the obtained cost function successfully avoids collisions with the environment in all scenarios and consistently remains the fitness function with the largest average distance to obstacles, at least 50% higher than other functions used in this study. [ABSTRACT FROM AUTHOR]

The mathematical modeling and the control problem of the paraglider recovery system (PRS) are investigated in this paper. A 9-degree-of-freedom dynamic model describing the paraglider recovery control system is modeled including the inside relative rotation, the apparent mass, and the payload's time-varying inertia. On the basis of the attitude tracking error system, a novel practical fixed-time attitude tracking control approach is then proposed. The attitude tracking error is governed to converge into the small regions of the origin with a fixed-time convergence rate. Moreover, this rate is independent of any initial states. Simulation results are finally presented to illustrate the PRS performance obtained from the proposed control scheme. • A new high-fidelity model of the paraglider recovery system is established with the payload's time-varying inertia considering. • A user-friendly model that facilitates the control design is derived from the high-DOF model. • A novel practical fixed-time attitude tracking controller is developed. • Precise attitude tracking performance and fast convergence rate are achieved by the proposed scheme. [ABSTRACT FROM AUTHOR]

The electrodynamic tether (EDT) system is used as one of the end-of-life disposal technologies to deorbit defunct satellites with the benefit of Earth's magnetic field and plasma environment. However, due to the flexibility of the conductive tether, the orbit-attitude coupling effects as well as the influence of Multiphysics fields, this system suffers from time-consuming computations using complicated mathematical model in long-term simulations. Therefore, this paper proposes a high-fidelity high-efficiency dynamics model for the EDT system, in which the tether libration and transverse motions are described by the articulated model, and the system equations are formulated using recursive dynamics algorithm. Computational cost of the recursive method is compared with a nonrecursive method, and the result shows that with the number of tether elements larger than 15, the recursive method would show better computational efficiency. Since the conductive tether tends to be kilometers long in application, this new model would definitely contribute to the numerical efficiency. In addition, simulations are conducted with 2 and 16 tether elements solutions. By comparing the obtained results, it is found that the two cases show large differences over time. For a long tether, it is reasonable to use a larger number of elements in the dynamics analysis. Besides, in order to suppress the libration motion and avoid unstable states in the EDT system, a current control strategy is proposed and verified by a deorbit simulation in low Earth orbit. • A high-fidelity high-efficiency model is proposed for the electrodynamic tether system. • The recursive method shows better efficiency with the number of elements larger than 15. • Different tether elements would result in large differences in simulation. • A current control strategy is proposed to stabilize the libration motion. [ABSTRACT FROM AUTHOR]

Compared with the two-valued memristor, the three-valued memristor has higher data density, richer dynamic characteristics, and more potential in digital logic and chaotic circuit. The present model of the three-valued memristor has several limitations. It doesn't perform well enough in three-valued applications since its hysteresis loops are linear and asymmetric. The mathematical model of the three-valued memristor with nonlinear and symmetric hysteresis loops is proposed in this research. To further investigate the electrical characteristics of the three-valued memristor, a circuit emulator of the memristor has been constructed with fundamental components. Multisim simulations and hardware experiments demonstrate the emulator's effectiveness. The three-valued memristor application in chaotic circuits shows fascinating dynamic characteristics and lays the foundation for future research. • The mathematical model of the three-valued memristor with nonlinear and symmetric hysteresis loops is proposed in this paper. • A circuit emulator of the three-valued memristor is proposed and verified using hardware and software. • The three-valued memristor application in chaotic circuits shows fascinating dynamic characteristics. [ABSTRACT FROM AUTHOR]

With the development of communications and transportation worldwide, the challenge of controlling epidemiological diseases becomes higher. The COVID19 has put all nations in a lethal confront with a severe disease that needed serious and painful actions. The sooner the actions, the less destructive the impact. In this paper, we incorporate what we believe is crucial but applicable to control the spread of COVID19 in the populations, that is, quarantine. We keep the model as simple as SI Kermack-McKendrick model with an additional compartment of quarantined patients. We established the system's basic properties and studied the stability of the disease-free equilibrium and its relation to the basic reproduction number R 0 in which we calculated its formula. The focus of our study is to measure the effect of quarantine rate on controlling the spread of COVID19. We use the data collected from the Ministry of Health in Saudi Arabia. We studied three different values of the quarantine rate where newly infectious patients are detected and isolated within 14, 7, and 5 days. The simulations show a significant effect of the quarantine where COVID19 can be fully controlled if the newly infected patient enters the quarantine within five days. These results were proposed to the Public Health Authority in Saudi Arabia and approved by the Ministry of Health in which they applied promptly. [ABSTRACT FROM AUTHOR]

This paper presents a novel directional observer-based fault detection and isolation scheme for second-order networked control systems (NCS). The directional unknown input observer (UIO) tool is exploited to study the problem of distributed fault detection and isolation (FDI). Two design schemes with global and partial/local network models are proposed to solve the distributed FDI problem. Thresholds are computed for the application of the proposed schemes in a noisy environment. In addition, the salient features of the proposed schemes are that both fault detection and fault isolation are achieved in a single step using a single observer. The schemes are applied to power system models to validate their results. A detailed comparison with existing FDI schemes is also provided, which clearly shows the effectiveness of the proposed scheme in terms of computational requirements. • The direction unknown input observer is used for distributed fault detection and isolation. • Distributed FDI schemes with and without complete mathematical model of the system are presented. • The developed schemes are more efficient in terms of computational burden. [ABSTRACT FROM AUTHOR]

Since the observed angle of a phase-locked loop (PLL) is relatively accurate even under distorted grid conditions, the mathematical model of the voltage errors caused by the switching modulation and the dead-time effect are derived as a function of the grid voltage angle in this paper. Based on the model analysis, an adaptive compensation algorithm is proposed to suppress the grid-side current harmonics in three-phase converters. The proposed algorithm fits the unmeasurable voltage errors by a truncated Fourier series expansion, and then takes it as an equivalent disturbance in the current control loop to achieve harmonic compensation. By the feed-forward compensation, the design and tuning of the controller parameters are simplified and separated from the dynamic performance. In addition, the controller can adapt to the grid frequency variation by updating the grid voltage angle with the PLL block. To reduce the computational burden, a simplified version of the proposed method is also presented. Simulation and experiment results show that the proposed methods can suppress the current harmonics and achieve better performance in terms of total harmonic distortion, strong robustness and insensitivity to the grid frequency variations, compared with the traditional PI control or repetitive control strategy. [Display omitted] • A PI controller is designed to ensure satisfactory dynamic performance. • An adaptive method is employed to compensate the voltage errors caused by the switching modulation and the deadtime effect so as to suppress the grid current harmonics. • A simplified adaptive strategy is also presented to reduce the computational burden and the complexity to half of the original method. • The adaptive algorithm is less model-dependent and built based on the grid voltage angle with a PLL to achieve frequency adaption. [ABSTRACT FROM AUTHOR]

• A model for the population dynamics of age-structured criminal gangs with correctional intervention measures is proposed. • The existence of backward bifurcation is determined by the adolescent population. • We fitted the gang model against the crime data and provide forecast for the cumulative number of reported cases. • Global sensitivity analysis is carried out to determine the parameters that strongly drive the dynamics of the model. • The existence of periodic trajectories (Hopf bifurcation) for the criminal gang model is studied. The prevalence of criminal gang activities in the society has continued to be a huge burden to mankind. Despite several attempts by the government and non-governmental organizations in curtailing the activities of criminal gangs, new criminal gangs are beginning to emerge with associated criminal cases on the high side, thereby causing social unrest. This paper examines the impact of correctional intervention measures on the population dynamics of the criminal gangs in Nigeria, following an age-structured paradigm. The existence of backward bifurcation is presented sequel to the coexistence of gang free equilibrium and gang endemic equilibrium when the reproduction number is less than unity. Also, the model exhibits periodic trajectories (Hopf bifurcation) as a result of coexistence among the criminal gang classes. Using the Nigeria crime data (from 1993 to 2013) as obtained from Elsevier Data in Brief, we analyze the criminal gang model quantitatively and provide the sociological implications of the results. The numerical results obtained from this work show that if at least 60 % of adolescents between 8–17 years who commit crimes are apprehended with prompt prosecution and correction, we can potentially eradicate adolescent delinquencies from the population and thus control the entire criminal gangs' population. [ABSTRACT FROM AUTHOR]

This paper discussed the relationship between angle and the value PvGRF for the execution of parachute landing. The value of PvGRF has been determined by using mathematical modelling principle of conservation of energy. The mathematical model describes the correlation between peak vertical ground reaction force and drop height. The peak vertical ground reaction force was used to determine the amount of force exerted on the parachutist during landing. A total of 21 parachutists from the Malaysian Army participated in this study comprising of three professional and eighteen amateur parachutists. Two cameras were utilised to capture the movements and thus generate kinematic information throughout the landing phase. The results showed that the estimated maximum peak vertical value of ground reaction force during the foot strike phase for professional and amateur parachutists were 3129 N and 4380 N respectively. Furthermore, the data showed that the professionals bent their hip and knees before their foot strike the ground. From the principle of biomechanics, this action increases the time and drop height during landing and thus reduce the peak vertical ground reaction force. Therefore, the hip and knee movement of the professional parachutist acts as a guideline for amateurs to reduce the impact force during landing. [ABSTRACT FROM AUTHOR]

• Bike repositioning problem with service requirements for rental and return requests was studied. • A mathematical model with the goal of minimizing the travel and unsatisfied costs was developed. • An efficient two-phase heuristic approach based on linear programming was proposed. • The proposed approach performs better than CPLEX optimizer and a genetic algorithm-based method. • The effects of various system parameters on the system were also investigated. An approach to overcome the bike imbalance problem is to transfer excess bikes to branches with bike shortages. This study develops a constrained mathematical model to deal with a multi-vehicle bike-repositioning problem, and aims to minimize the sum of transportation and unmet demand costs over a planning horizon through bike-transfer strategies under a minimum service requirement. A two-phase heuristic based on linear programming was proposed to solve the problem and produce compromising solutions. In the first phase, the paper developed a linear programming model to quickly develop decisions related to bike inventory, unloading, and loading for all stations for each time slot. In the second phase, this paper proposed an iterative approach through two parameter sensitive mathematical models to sequentially reduce the problem scale to develop decisions related to bike transfers. Computational results show that the proposed approach is superior to a CPLEX optimizer and a hybrid heuristic based on a genetic algorithm. The proposed approach was used to analyze the bicycle system in Taiwan. The impacts of various system parameters on the system were also investigated. [ABSTRACT FROM AUTHOR]

• This paper presents mathematical models that address the simultaneous evacuation of victims and entrance of responders. • Solutions provide the optimal routes for evacuees and responders within a critical timeframe. • Four types of models are developed according to the three different degrees of the golden time. • A heuristic algorithm is developed by extending the capacity constrained route planner. This paper presents mathematical models and a heuristic algorithm that address a simultaneous evacuation and entrance planning. For the simultaneous evacuation and entrance planning, four types of mathematical models based on the discrete time dynamic network flow model are developed to provide the optimal routes for evacuees and responders within a critical timeframe. The optimal routes obtained by the mathematical models can minimize the densification of evacuees and responders into specific areas. However, the mathematical model has a weakness in terms of long computation time for the large-size problem. To overcome the limitation, we developed a heuristic algorithm. We also analyzed the characteristics of each model and the heuristic algorithm by conducting case studies. This study pioneers area related to evacuation planning by developing and analyzing four types of mathematical models and a heuristic algorithm which take into account simultaneous evacuation and entrance planning. [ABSTRACT FROM AUTHOR]

• A realistic PHS model is proposed for energy management applications. • Flow rate, water level, evaporation and precipitation affect model performance. • The proposed PHS model is validated with experiments in different operating points. • The error of the estimated stored water is reduced from 13.17% to 0.74%. This paper proposes a comprehensive pumped hydro storage model with applications in microgrids and smart grids. Existing models within current literature produce high error in calculating stored energy since some critical parameters are ignored. Thus, they are not suitable choices for energy management applications. Accordingly, the main objective of this study is to provide a more realistic model by estimating all the essential parameters in the system. First, all the losses due to the pump, pipes, and fittings are modelled. Next, a water balance approach is used to calculate the volume of water in the upper reservoir considering inflow, outflow, precipitation, and evaporation. Finally, the turbine power is calculated as a function of the water level in the reservoirs, considering the hydraulic losses of the turbine, pipes and fittings. The proposed model is validated using the experimental results of a physical system. The accuracy of the model is compared with other established models. The results demonstrate that the proposed model decreases the error of the estimated stored energy from 13.17% to 0.74%. Moreover, this study shows the capability of the model to simulate different configurations. The model provided in this paper assists researchers in the field and is of benefit to engineers in designing, sizing, and managing pumped hydro storage systems. [ABSTRACT FROM AUTHOR]

• A mathematical model of rolling force imbedding the deformation penetration coefficient is established. • The rolling force is positive correlation with the deformation penetration coefficient and the roller velocity. • The larger the reduction and the ratio of the plate thickness to diameter are, the bigger the required rolling force are. The deformation characteristic of an ultra-heavy plate in thickness direction is described by introducing a parameter, called deformation penetration coefficient, and the rolling force model taking this parameter into account in the broadside stage is established. In this paper, the deformation penetration coefficient is defined as the ratio of the actual deformation depth to the overall plate thickness, which is shown as the function of the initial thickness, the pass reduction and the critical shape factor. Since the plate width speard can be neglected during broadside rolling, a two-dimensional velocity field is constructed by simplifying a classical three-dimensional velocity field. For the purpose of solving the problem of functional integration originated from the nonlinear Mises specific plastic power, the simplified velocity field is analyzed by the geometric approximation (GA) yield criterion, and the internal deformation power is obtained. Moreover, the friction power and the shear power are obtained by the inner product method of the strain vector and the mean velocity intergral method, respectively. The analytical solution of rolling force is obtained by the variational method, and its value for each pass is compared with the measured data from a domestic factory. The comparison result shows that the rolling force model in this paper has a high predictive accuracy, since the maximum error is less than 8.6%. The rolling parameter analysis shows that the deformation penetration coefficient, the pass reduction and the ratio of plate thickness to diameter affect the rolling force of the ultra-heavy plate apparently. [ABSTRACT FROM AUTHOR]

Purpose: Due to the gradual transformation and upgrading of traditional medical industry, online health has become a hot spot recently. Various empirical researches have explored the critical factors that affect users' adoption behavior of online health, but their conclusions cannot be completely unified. Therefore, this paper aims at providing an integrated analysis, so as to explore the strength of the proposed online health adoption model's path relationship and the moderating effect of economic development level by dividing the sample into two subgroups, developed countries or areas and developing countries or areas.Design/methodology/approach: This paper conducted a meta-analysis by synthesizing the effect sizes extracted from a total of 43 articles including 46 empirical studies, which were searched from a variety of journals, conferences, book chapters and theses.Findings: Results show that all combined effect sizes of the proposed conceptual model are statistically significant and indicate that the users' adoption behavior of online health is mainly affected by perceived ease of use, perceived usefulness and subjective norm, rather than perceived behavioral control, innovativeness and trust. Furthermore, the moderator analysis confirms that the economic development level does have a moderating effect on the two relationships, perceived ease of use - perceived usefulness and innovativeness - behavioral intention. Specially, results manifest that the impact of perceived ease of use toward perceived usefulness receives more attention in developed countries or areas, while the impact of innovativeness toward behavioral intention is more noteworthy in developing counties or areas.Originality/value: This paper was conducted with the view of obtaining a unified conclusion about the research field of online health adoption. Its content is original. Whether in the academia or industry, the findings of this research will have implications for the future development of online health. [ABSTRACT FROM AUTHOR]

• Developing a novel mathematical inventory model for growing-mortal items. • Studying the proposed model for trout fish production in a two-echelon supply chain (case study). • Applying revenue-sharing contract as well as revenue and cost sharing contract into proposed model. • Proposing a new feeding function for rainbow trout. • Providing managerial insights into trout production in a coordinated supply chain. Unlike the extensive inventory models for both ameliorating and deteriorating items, incorporating some specific features of these products have mostly been neglected. To fill this research gap, providing an appropriate mathematical inventory model for both ameliorating and deteriorating items is of paramount importance. In this regard, this paper proposes a novel mathematical inventory model for products called growing-mortal items in a two-echelon supply chain consisting of one supplier and one farmer. The proposed inventory model is more precise than analogous inventory models due to the fact that the specific growth function for the item is considered as well as mortality rate. As a case study, the model is applied to rainbow trout, which can be used for other types of growing-mortal items. Moreover, a feeding function is first-ever proposed for rainbow trout regarding the case study. The goal of this paper is to study the growth period in the supplier and then in the farmer sites to maximize the profit of the supplier as a leader and farmer as a follower under a Stackelberg game. To demonstrate how to reduce the inventory system costs by two coordination mechanisms, namely revenue-sharing and revenue and cost sharing, the model is solved under centralized and decentralized cases. Finally, sensitivity analysis on key parameters is also conducted to derive some managerial insights. [ABSTRACT FROM AUTHOR]

This paper focuses on the dynamic stability of spinning missiles equipped with two-loop autopilot considering the seeker disturbance rejection rate parasitical loop (DRRPL) effect induced by attitude disturbance of projectile. The representative mathematical model of spinning missiles in the non-spinning coordinate system is established, and the cross-coupling effect between the pitch and yaw induced by the rotation motion of missile body is analyzed and decoupled. The two-loop acceleration autopilot for each channel is designed with the conventional design method, and the relationship between the autopilot gains and the expected design indexes is deduced. A proportional navigation guidance (PNG) system model with consideration for the seeker DRRPL is further proposed in the form of complex summation. After strict mathematic deduction, the sufficient and necessary condition of the dynamic stability for spinning missiles is obtained. Numerical simulations and discussions under different cases are conducted to demonstrate the validity of stability condition. The results indicate that the stability of a spinning missile is closely related to the amplitude of the seeker DRR, the rolling rate, and the autopilot design indices. The stable region of the autopilot design frequency is obtained by solving the dynamic stability condition. To meet the requirement of stable controlling at a constant spinning rate, it was found to be effective to decrease the amplitude of the seeker DRR for spinning missiles, employ the lead angle decoupling approach to the commands for the servo system, and guarantee that the autopilot design frequency is lower than the critical value. The dynamic stability condition derived in this paper is useful for evaluating the stability of a spinning missile with consideration for the seeker DRRPL, and the conclusions obtained can provide guidance for the autopilot design of spinning missiles. [ABSTRACT FROM AUTHOR]

This paper considers the lot scheduling problem in the flexible flow shop with limited intermediate buffers to minimize total cost which includes the inventory holding and setup costs. The single available mathematical model by Akrami et al. (2006) for this problem suffers from not only being non-linear but also high size-complexity. In this paper, two new mixed integer linear programming models are developed for the problem. Moreover, a fruit fly optimization algorithm is developed to effectively solve the large problems. For model's evaluation, this paper experimentally compares the proposed models with the available model. Moreover, the proposed algorithm is also evaluated by comparing with two well-known algorithms (tabu search and genetic algorithm) in the literature and adaption of three recent algorithms for the flexible flow shop problem. All the results and analyses show the high performance of the proposed mathematical models as well as fruit fly optimization algorithm. • This paper considered lot scheduling problem in hybrid flow shops with limited buffer. • Two mixed integer linear programming models are proposed for the first time. • A novel metaheuristic based on the fruit fly algorithm is proposed for the problem. • The proposed models and algorithm significantly outperform the available model and algorithms. [ABSTRACT FROM AUTHOR]

• Identified possible design options of CHERs. • Performed mathematical modeling of CHERs incorporating mixing effect for complex reaction schemes. • Exhibited capabilities of CHERs to carry out rapid and highly exo- or endo-thermic reactions. • Demonstrated that a single flexible CHER can be used to carry out multiple reaction schemes with minor modifications. Objective of this paper is to contribute towards overcoming the barriers limiting industry scale applications of the Compact Heat Exchanger Reactor (CHER). This objective could be achieved by exhibiting capabilities of the CHERs to carry out rapid and highly exo- or endo-thermic chemical reactions. Also, classification of CHERs and preparation of guidelines for the selection of CHERs for the given application (without the needs of extensive experimentation requirements) could prove to be helpful. In order to achieve these, several possible design options of CHERs have been identified and mathematical modelling of these design options has been carried out. The main purpose of the modelling work is to understand the impact of different designs on the rate and product distribution of single liquid phase multiple chemical reactions. The results achieved exhibit capabilities of the CHER to carry out rapid and highly exo- or endo-thermic multiple chemical reactions. The results also serve as a tool to check suitability of different designs of the CHER to carry out more than one type of reaction schemes. The development and results of the mathematical modelling for the CHER are discussed in this paper. The conclusions suggest that a single flexible CHER can be used to carry out multiple reaction schemes with minor modifications. [ABSTRACT FROM AUTHOR]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Abstract The mathematical model of heating substation, which is an important part of district heating system, is presented in this paper. The main components of district heating substation system, from the automatic control perspective, that are observed in this paper are heat exchanger and three-way valve. Presented mathematical model is developed so it could operate in real-time, since the crucial aspect of development, deployment and testing of new control techniques and optimization algorithms is their accurate validation on the real system. However, the accessibility to a real system is often not possible. Corresponding to this, an alternative is the existence of the correct mathematical model of a process, with the ability to operate in real-time. First, the presented mathematical model of district heating substation is decomposed to the simpler models of its main elements, in order to provide the analysis of the various parameters on the model performance through numerical simulation. Second, a real-time model is developed in LabVIEW software package and deployed on the embedded controller with a real-time processor as a three-layer application which enables data acquisition and communication with a programmable controller. [ABSTRACT FROM AUTHOR]

Abstract Corruption is one of the barriers to achieving sustainable development goals (SDGs), which is associated with the lack of integrity. The objective of the paper is to examine the extent of integrity framework information disclosure on Malaysian and Indonesian local authorities' websites using the coercive isomorphism tenet. The data collected in this study were based on a content analysis of inclusion or exclusion of integrity framework information disclosed on 51 Malaysian and 34 Indonesian local authorities' websites. This paper is significant for the following reasons. Based on the website disclosures, the 34 Indonesian local authorities or provinces outperformed Malaysia's 51 city and municipal councils' disclosures. The average website disclosure for Indonesia was 29 items out of 47 items under study as compared to just four items disclosed in Malaysia. Indonesian local authorities are more proactive in the integrity initiative implementation, which is translated into reporting as influenced by the external coercive forces: legitimacy, public visibility, public sector reform and institutional support structures. The findings would assist in helping regulatory authorities and policy makers to strengthen their mechanisms in upholding integrity. This paper considers the institutional theory of isomorphism mechanism, namely, coercive that enhances the understanding of integrity framework disclosure and adds to the pool of literature. Graphical abstract Image 10581 Highlights • The Indonesian local authorities disclose more online integrity framework info. • Coercive factors influence the disclosure by the Indonesian local authorities. • More enforcement is required to promote online integrity information in Malaysia. • Online integrity disclosure drives the attainment of sustainable development goal. [ABSTRACT FROM AUTHOR]

Abstract Sensitivity analysis provides information on the relative importance of model input parameters and assumptions. It is distinct from uncertainty analysis, which addresses the question 'How uncertain is the prediction?' Uncertainty analysis needs to map what a model does when selected input assumptions and parameters are left free to vary over their range of existence, and this is equally true of a sensitivity analysis. Despite this, many uncertainty and sensitivity analyses still explore the input space moving along one-dimensional corridors leaving space of the input factors mostly unexplored. Our extensive systematic literature review shows that many highly cited papers (42% in the present analysis) fail the elementary requirement to properly explore the space of the input factors. The results, while discipline-dependent, point to a worrying lack of standards and recognized good practices. We end by exploring possible reasons for this problem, and suggest some guidelines for proper use of the methods. Highlights • A systematic review of 280 scientific papers mentioning sensitivity analysis has been performed. • The analysis addresses the use of SA in the context of mathematical modelling, focusing on highly cited works. • Many highly-cited papers (42% in the present analysis) present a SA of poor quality. • The results, while discipline-dependent, point to a worrying lack of standards and good practices. • Some guidelines for proper use of the methods are suggested. [ABSTRACT FROM AUTHOR]

This paper focuses on training the mathematical models for prediction of optimal livestock feed blend for animal. In this paper, three functions are trained to find the most optimal percentage of price, nutrients and water. For this purpose three objective functions has been prepared using corresponding values of feed ingredients and an algorithm is developed using ANN. The objective functions are trained with 5000 random values to find the optimized results and prediction ability is compared with existing model. Developed algorithm shows superiority over the existing programming models. [ABSTRACT FROM AUTHOR]

Highlights • CFD and Global Energy Balance (GEB) to simulate a solar chimney were analyzed. • There are few calculation tools based on transient models for the dimensioning of solar chimneys. • GEB models predict the dynamic behavior in relatively short times and one can integrate them with Building Energy Simulation programs. • Results of a solar chimney using a PCM show that the airflow was available in evening and night periods. • This review paper is a reference for future research into the field of solar chimneys with a PCM and its applications. Abstract The solar chimney is one concept explored by building engineers and designers for reducing heat gain and inducing natural cooling in both commercial and residential buildings. In this sense, scientists around the world have developed significant research on solar chimneys since the 1990s. This review presents the studies related to the numerical thermal modeling of both, conventional solar chimneys and solar chimneys with phase change materials (PCM). The article focuses on two research areas: Computational Fluid Dynamics (CFD) and Global Energy Balance (GEB). Based on the literature, the CFD approach has become a powerful tool to investigate several aspects concerning the heat transfer mechanisms in a solar chimney. Additionally, the analysis of the literature showed that few calculation tools based on CFD transient state models of solar chimneys are available because the computational time required to solve these models could be excessive and impractical. Therefore, the use of high-performance computing (HPC) will be necessary to continue using CFD. On the contrary, the GEB models predict the transient behavior of these systems in short times, and one can integrate them in Building Energy Simulation programs. However, the literature about the solar chimney modeling using GEB shows that the transient mathematical model with PCM (six research papers) has been less used than the steady-state model. In general, results of a solar chimney using a PCM show that the temperature variation of PCM and air in the chimney were available for the natural ventilation in evening and night periods. Finally, this review paper is a reference for future research into the field of solar chimneys with a PCM and its applications. [ABSTRACT FROM AUTHOR]

Abstract The aim of this paper is to draw readers' attention to potential new technological solutions for effective utilisation of dispersed biomass resources in distributed community-scale applications. In the paper conceptual system, that consists of allothermal wood gasifier, solid oxide fuel cell (SOFC), internal combustion piston engine (ICE) and Organic Rankine Cycle (ORC) for waste heat recovery, is proposed. Configuration of such systems is nowadays possible due to availability individual small-scale energy conversion technologies that can be integrated into complex structures. In the studied case the anode exhaust gas of the syngas fired SOFC module, that still contains combustible gases, is considered a secondary fuel for a bottoming ICE. The ORC cycle module is driven by the heat recovered from process gas coolers as well as from SOFC cathode and ICE exhaust gases. The system has been theoretically evaluated in terms of energy conversion efficiency and profitability using thermodynamic and economic analysis. Relevant robust mathematical models of key components have been developed. Through the modelling the most important performance parameters are addressed. Electric power of the sample system is below 1 MW what makes it suitable for utilisation of locally available biomass. Simulations revealed potentially high value of the net biomass energy to electricity conversion efficiency of 37%–40% depending on the ORC cycle configuration. Financial analysis revealed positive values of profitability indices at current level of market prices. The results are compared with a real biomass-fired ORC cogeneration project. The system also addresses issues related to external effects of the project, such as global emission reduction and primary energy savings. Highlights • Integrated gasification cogeneration plant of complex structure is proposed. • Internal combustion gas engine is proposed as bottoming unit for solid oxide fuel cell. • Evaluation of the concept is performed using mathematical modelling approach. • Technical analysis reveals substantial efficiency gains, fuel savings and emission reduction. • System profitability is estimated under current market and policy conditions. [ABSTRACT FROM AUTHOR]

Abstract Unbalanced construction bidding covers different allocations of mark-up between contract project items to attempt and increase win chances with unbalance but without changing of total bid price. Many models have been developed to increase both the systemized execution and detection of unbalancing but, although unbalancing is thought to be widespread in general, substantially not known it use. Proposed unbalanced construction bidding models of many researchers neglected part of improve profitability. This paper inspects and integrates the construction bidding models techniques for determining price of each unit quantity and take advantage of bidder benefits, then all proposed mathematical models is studied carefully and more modifications will be done to tries to be fair and equitable for providing owner quantities that impact directly on items prices. Finally it was concluded that the maximum/minimum models are preferred for many world cases. At end of paper, a case of study will be presented to demonstrate the use of proposed models for optimizing project bidding. Also, this paper will serve as a guide for construction project stakeholders with effective management to perform a competitive level of project pricing. [ABSTRACT FROM AUTHOR]

Abstract The paper discusses a niche area problem — the design of reduced-order multiple observers which can achieve the finite-time state reconstruction for Takagi–Sugeno multiple models with unknown inputs. The new reduced-order multiple observer obtained in this paper is only the second ever designed, the author of this paper continuing his work started one year ago with the introduction of the reduced-order multiple observer concept. The obtaining of the new reduced-order multiple observer is achieved by combining two classical reduced-order observers for linear time-invariant multivariable systems with unknown inputs and a full-order multiple observer for Takagi–Sugeno systems. The main innovative idea behind the design of the reduced-order multiple observer for Takagi–Sugeno systems described by the multiple models is the split of the multiple model into two subsystems: an unknown-input-free subsystem and an unknown-input-depending subsystem. The unknown-input-free subsystem is brought to the form of a standard multiple model and, in this situation, any algorithm to design full-order multiple observers can be used in the design of reduced-order multiple observers. The steps of the design procedure have been summarized and software implemented; then, the validation of the suggested algorithm has been done for two concrete cases associated to the motion of an aircraft during its landing Highlights • Paper discusses a niche area problem-design of reduced-order multiple observers. • The reduced-order observer designed is only the second one ever obtained. • The steps of the design procedure have been summarized and software implemented. • The observer's performances are compared with the ones of other observers. [ABSTRACT FROM AUTHOR]

Abstract Problems were discussed about the published equation coefficients of Tong and coworkers [Fluid Phase Equilibria 427 (2016) 549–556] for describing mathematically the ethenzamide solubility in different pure solvents using the NRTL model and Wilson model. The back-calculated values using the reported parameters' values for the two models are not the solubility as stated in the published paper. Larger deviations were observed between our back-calculated data and those reported in the authors' published paper. The expression of NRTL model was corrected and the parameters of the two equations were re-analyzed. [ABSTRACT FROM AUTHOR]

Abstract Consolidation of a prepreg layup to a target thickness is critical in order to achieve the required fibre volume fraction and dimensions in a composite part. Experiments show that different processing conditions lead to different levels of compaction and variability in the thickness. This paper presents an analysis of processing conditions and their effects on consolidation of thick composite components. A model that accounts for both percolation and squeezing flow is employed to study two toughened prepreg systems – IM7/8552 and IMA/M21. This paper analyses the significance of the process parameters on the thickness of prepregs and its variability. The analysis of different layups and processing conditions suggests several strategies to control target thickness and its variability. The IMA/M21 prepreg system was found to have lower variability due to its toughening mechanism. The presented results provide a better understanding of the composite manufacturing and can be used to provide an informed choice in design for manufacture of composite structures. [ABSTRACT FROM AUTHOR]

Highlights • The mathematical model of corrugated shells with special shapes is presented. • Effect of corrugation parameters on critical load is investigated. • Linear and nonlinear buckling analyses are conducted. • Critical load of corrugated shells is compared to smooth ones. • Specific range of corrugation parameters significantly increase the value of relative critical load. Abstract The problem of elastic stability of the shells with special shapes with corrugated middle surfaces under external pressure is debated in the presented paper. Solution of the problem is based on FEM study. Corrugated barrelled, pseudo-barrelled, and cylindrical shells of constant mass are considered. Geometrical modification of the middle surface geometry is based on sine wave along principal directions. Middle surface of the corrugated shells are described referring to differential geometry of surfaces by parametric functions in three-dimensional Euclidean space. Linear and nonlinear buckling analyses are conducted. Examples of buckling modes are presented, which differ significantly from those typical for shells of revolution with positive or zero Gaussian curvature. It is proven that corrugation may lead to serious increase or decrease of critical load for all types of presented shells. [ABSTRACT FROM AUTHOR]

Abstract The development of irrigated agriculture is vital to nourish the burgeoning world population but without apposite drainage stipulations, this development can result in environmental problems of salinization and waterlogging in irrigated agro-systems. These problems of irrigated areas were generally assessed by conventional methods which demand a lot of data. The progress in computer technology has offered the ability to precisely simulate hydrologic and agricultural processes more readily than expensive and time-consuming field trials. This paper provides an overview of the applications of various computer-based mathematical models in managing the poor drainage-induced salinization and waterlogging problems of agricultural areas. The analysis of past literature revealed that a universally appropriate and all-purpose model is not available yet because each model has its advantages, disadvantages and limitations, and data requirements. The paper, first, presents an introduction of the salinization and drainage problems of agricultural areas along with the implication of the study which is followed by the background of the problems. Then the application of DRAINMOD and other computer-based models for solving the problems are detailed. It also deals with the integrated use of diverse models for managing the salinization problems. The relevant case studies pertaining to the applications of various mathematical models across the world are described and conclusions of the study are summed up. Graphical abstract Image Highlights • An overview of environmental problems of salinization and drainage is presented. • The rationale of the environmental problems of irrigated areas is provided. • The use of DRAINMOD and diverse models for solving the problems is detailed. • The integrated use of diverse models for managing the problems is discussed. • Case studies of uses of diverse mathematical models across the world are described. [ABSTRACT FROM AUTHOR]

An in-plane elasto-plastic material model and a hygroexpansivity-shrinkage model for paper and board are introduced in this paper. The input parameters for both models are fiber orientation anisotropy and dry solids content. These two models, based on experimental results, could be used in an analytical approach to estimate, for example, plastic strain and shrinkage in simple one-dimensional cases, but for studies of the combined and more complicated effects of hygro-elasto-plastic behavior, a numerical finite element model was constructed. The finite element approach also offered possibilities for studying different structural variations of an orthotropic sheet as well as buckling behavior and internal stress situations under local strain differences. A few examples are presented of the effect of the anisotropy and moisture streaks under stretching and drying conditions on strain differences and buckling. The internal stresses were studied through a case in which the drying of different layers occurred at different stages. Both the anisotropy and moisture streaks were capable of rendering the buckling of the sample visible. The permanency of these defects highly depends on several process stages and tension conditions of the sheet, as demonstrated in this paper. The application possibilities of the hygro-elasto-plastic model are diverse, including investigation into several phenomena and defects appearing in drying, converting and printing process conditions. [ABSTRACT FROM AUTHOR]

Highlights • A comprehensive method is proposed to compute the mesh stiffness of the spur gear pairs. • Two coupling models are developed to obtain the mesh stiffness of helical gear pairs. • The novel methods present a more accurate result compared to previous methods. Abstract This paper presents a novel calculation method to accurately determine the mesh stiffness of spur and helical gears. Firstly, based on the integral potential energy method, a comprehensive method is proposed to compute the mesh stiffness of the spur, obtaining more accurate results compared to previously used methods. Secondly, the proposed method for spur gears is then used to develop two models, single coupling and double coupling models, to calculate the mesh stiffness of helical gear pairs. The effects of coupling stiffness in both the single coupling and double coupling models are investigated. The main conclusion is drawn that the methods proposed in this paper can be used to accurately compute the meshing stiffness of spur and helical gears. [ABSTRACT FROM AUTHOR]

Highlights • A topology-based rigid spherical quadrilateral mesh method is proposed in this paper. • The nondifferentiable problem of free-form surface is solved based on topological transformation. • The model of feature extraction for free-form surface based on topological transformation is built. • The tangent bundle of smooth free-form surface manifold is analyzed. Abstract Free-form surface reconstruction is the key technology of mathematical modeling of engineering. It is important for accurate reconstruction of the entity model that conforms to the design. In order to improve the measurement accuracy of the workpiece, a method for free-form surface feature recognition based on topological transformation is proposed in this paper. Firstly, the information of scanning points is expressed as the form of topological space. Based on this, a method of surface constructing that selects the natural-quadratic-surface as the manifold of free-form surface is proposed. Then, the free-form surface that is constructed from the original point cloud is transformed into a smooth free-form surface which is homeomorphic to the original free-form surface based on the theory of topological embedding. The features of the transformed free-form surface can be easily analyzed and recognized. Finally, the qualitative description of an arbitrary point on the surface is obtained by analyzing the tangent bundle of smooth free-form surface manifolds. The feature recognition of free-form surface for workpiece is realized. The experimental results on workpiece model are reported in this paper, which validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Highlights • This paper considers a stochastic HIV-1 infection model with Beddington-DeAngelis incidence rate. • Sufficient conditions for extinction of the disease are established. • Criteria for the existence of a stationary distribution are given through constructing suitable Lyapunov functions. • A threshold value for the disease to disappear or prevail is obtained. Abstract In this paper, we consider a stochastic HIV-1 infection model with Beddington-DeAngelis incidence rate. Before exploring its long-time behavior we show that there is a global positive solution of this model. Then sufficient conditions for extinction of the disease are established. Moreover, we give sufficient conditions for the existence of a stationary distribution of the model through constructing a suitable stochastic Lyapunov function. The stationary distribution implies that the disease is persistent in the mean. Therefore, a threshold value for the disease to disappear or prevail is obtained. Finally, some numerical examples are illustrated to support our theoretical results. [ABSTRACT FROM AUTHOR]