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This article presents a semi-empirical model of Proton Exchange Membrane Fuel Cell (PEMFC), combining electrical, thermal and ageing phenomena. This modelling approach links activation and diffusion phenomena in order to create a new PEMFC model, close to reality in steady state and enabling fast simulation (since the dynamics are of first order). The purpose of this model is to enable energy management studies to optimise the design, lifetime and consumption of a PEMFC system. The degradation model is defined and fitted according to a PEM fuel cell datasheet. The design aims to study fault-tolerant multi stack Fuel Cell (MFC) systems, to consider their interactions with power converters and to design optimal control and adaptive management rules. The degradation model helps to define management rules according to the state of health and to the degradation speed of each stack. This work also presents an analysis of the existing models available in the literature and more specifically models compatible with the needs of Modular Fuel Cells (MFC) studies. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the paper is to better measure the risks and volatility of the Bitcoin market by using the proposed novel risk measurement model. Design/methodology/approach: The joint regression analysis of value at risk (VaR) and expected shortfall (ES) can effectively overcome the non-elicitability problem of ES to better measure the risks and volatility of financial markets. And because of the incomparable advantages of the long- and short-term memory (LSTM) model in processing non-linear time series, the paper embeds LSTM into the joint regression combined forecasting framework of VaR and ES, constructs a joint regression combined forecasting model based on LSTM for jointly measuring VaR and ES, i.e. the LSTM-joint-combined (LSTM-J-C) model, and uses it to investigate the risks of the Bitcoin market. Findings: Empirical results show that the proposed LSTM-J-C model can improve forecasting performance of VaR and ES in the Bitcoin market more effectively compared with the historical simulation, the GARCH model and the joint regression combined forecasting model. Social implications: The proposed LSTM-J-C model can provide theoretical support and practical guidance to cryptocurrency market investors, policy makers and regulatory agencies for measuring and controlling cryptocurrency market risks. Originality/value: A novel risk measurement model, namely LSTM-J-C model, is proposed to jointly estimate VaR and ES of Bitcoin. On the other hand, the proposed LSTM-J-C model provides risk managers more accurate forecasts of volatility in the Bitcoin market. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to analyse the main variables and causal relationships in the system structure of the diversification of non-agricultural activities on agricultural holdings using system dynamics (SD) modelling. The SD model aims to simulate depictions of the behaviour of the real system while testing the effects of alternative decisions over time. Design/methodology/approach: An SD methodology was chosen to model diversification in farm tourism. Findings: A system approach increases the authors' understanding of the transition of agricultural holdings to farm tourism. The results indicate that the transition to farm tourism depends on the level of tourism development in a certain area. The system is influenced by subsidies allocated by authorities to expand primary agricultural activities. The model describes a situation in which the tourism and agricultural industries have been affected by the COVID-19 pandemic. Research limitations/implications: The research is limited by the small set of available data due to the limited number of farms in Slovenia. One major problem is the difference in statistical data on the same activity collected from different institutions in Slovenia. Practical implications: The paper includes implications for understanding the transition process to farm tourism, allowing policymakers to experiment with subsidies and promotion to explore the efficacy and efficiency of proposed policies. Originality/value: This study provides a structured, systemic view of the diversification of non-agricultural activities on agricultural holdings, where the simulation results are a reliable reflection of the behaviour of the actual system being modelled. [ABSTRACT FROM AUTHOR]

Time series modelling has a wide spectrum of applications in several fields including engineering and finance. Most traditional modelling techniques rely on assumptions related to the input data and manual pre-processing, based on user observations, rendering them unsuitable for analysing time-series with varying characteristics automatically, while more general modelling techniques usually require increased computational work for application and tuning. Recently, a general modelling framework based on a recursive Schur complement technique, that utilizes an adaptively determined set of basis functions, has been proposed. Herewith, a novel modified approach based on recursive incomplete pseudoinverse matrices in conjunction with preconditioned iterative methods for large datasets, is proposed. This sparse approach greatly reduces storage requirements and the recursive nature of the procedure avoids recomputation of the preconditioner after addition of a new basis function. Moreover, update of the coefficients for a different window of data and predefined basis functions can be performed utilizing the incomplete pseudoinverse matrix as preconditioner. The case of sinusoidal basis functions is presented along with a novel adaptive frequency estimation technique. The stability of the resulting model is discussed with respect to the choice of basis functions. The case of basis derived from machine learning techniques is also discussed. Numerical results are given depicting the applicability, generality and effectiveness of the proposed technique. Comparative results with other methods show forecasting RMSE improvement between 7% to 80%, for the majority of the chosen time series. [ABSTRACT FROM AUTHOR]

Diverse modelling techniques in cholera epidemiology have been developed and used to (1) study its transmission dynamics, (2) predict and manage cholera outbreaks, and (3) assess the impact of various control and mitigation measures. In this study, we carry out a critical and systematic review of various approaches used for modelling the dynamics of cholera. Also, we discuss the strengths and weaknesses of each modelling approach. A systematic search of articles was conducted in Google Scholar, PubMed, Science Direct, and Taylor & Francis. Eligible studies were those concerned with the dynamics of cholera excluding studies focused on models for cholera transmission in animals, socio-economic factors, and genetic & molecular related studies. A total of 476 peer-reviewed articles met the inclusion criteria, with about 40% (32%) of the studies carried out in Asia (Africa). About 52%, 21%, and 9%, of the studies, were based on compartmental (e.g. , SIRB), statistical (time series and regression), and spatial (spatiotemporal clustering) models, respectively, while the rest of the analysed studies used other modelling approaches such as network, machine learning and artificial intelligence, Bayesian, and agent-based approaches. Cholera modelling studies that incorporate vector/housefly transmission of the pathogen are scarce and a small portion of researchers (3.99%) considers the estimation of key epidemiological parameters. Vaccination only platform was utilized as a control measure in more than half (58%) of the studies. Research productivity in cholera epidemiological modelling studies have increased in recent years, but authors used diverse range of models. Future models should consider incorporating vector/housefly transmission of the pathogen and on the estimation of key epidemiological parameters for the transmission of cholera dynamics. • Compartmental models are the most widely used modelling techniques in cholera epidemiology. • Studies that integrated the vector/housefly transmissions of the pathogen into the cholera model are scarce. • Small portion of studies considered the estimation of key epidemiological parameters for the transmission of cholera dynamics. • Vaccination only platform was utilized as a control measure in more than half of the studies considered. [ABSTRACT FROM AUTHOR]

Locally-active memristor (LAM) is one of the promising candidates of artificial neurons, indicating it has potential applications in neuromorphic computing. Quantitative theoretical analysis on LAMs can provide benefits for designing related oscillator circuits and systems. This study begins with the aim of assessing the importance of DC V-I characteristic in the performance of LAMs by using small-signal analysis method. The DC V-I curve of the LAM is specified by two parameters involving resistance (conductance) and differential resistance (differential conductance). In addition to these two static parameters, we extract a crucial dynamic parameter to describe the behavior of the LAM. Theoretical analysis demonstrates that the performance of generic current-controlled and voltage-controlled LAMs is closely associated with three crucial parameters, i.e., the above two static and one dynamic parameters. Hence, only based on these three parameters, can one derive the small-signal equivalent circuit of LAMs and determine the oscillation frequency range and condition for simple LAM-based oscillators. By applying the presented universal dynamics analysis results, we further propose a modified mathematical model with higher accuracy to mimic the quasi-static and oscillating behaviors of a real Nb2O5 device, and provide some fundamental guidance for the design of LAM-based high-frequency oscillators. [ABSTRACT FROM AUTHOR]

Memristive technology has experienced explosive growth in the last decade, with multiple device structures being developed for a wide range of applications. However, transitioning the technology from the lab into the marketplace requires the development of an accessible and user-friendly design flow, supported by an industry-grade toolchain. In this work, we demonstrate the behaviour of our in-house fabricated custom memristor model and its integration into the Cadence Electronic Design Automation (EDA) tools for verification. Various input stimuli were given to record the memristive device characteristics both at the device level as well as the schematic level for verification of the memristor model. This design flow from device to industrial level EDA tools is the first step before the model can be used and integrated with Complementary Metal-Oxide Semiconductor (CMOS) in applications for hybrid memristor/CMOS system design. [ABSTRACT FROM AUTHOR]

The paper deals with mathematical modelling and the control system for UltraFast Charging Stations (UFCS) based on DC micro-grid concept and Energy Storage System Integration to feed new Electrical Vehicles (EVs) at 800V DC in order to reach the EVs power requirement for charge-time less than 10 min. The UFCS integrates a battery energy storage system (BESS) to reduce the peak power of AC main grid, decoupling the dynamics of the DC charging station from the AC grid by means of its dedicated control system. Designing procedure and Control Strategy, based on Load Levelling power management, are dealt with numerical simulation results in Matlab-Simulink software, presented in order to verify UFCS performance and the charging station's dynamics. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this paper is to provide the theoretical conceptualization of a bandpass (BP) negative group delay (NGD) microstrip circuit. The main objective is to provide a theorization of the particular geometry of the microstrip circuit with experimental validation of the NGD effect. Design/methodology/approach: The methodology followed in this work is organized in three steps. A theoretical model is established of equivalent S-parameters model using Y-matrix analysis. The GD analysis is also presented by showing that the circuit presents a possibility to generate NGD function around certain frequencies. To validate the theoretical model, as proof-of-concept (POC), a microstrip prototype is designed, fabricated and tested. Findings: This work clearly highlighted the modelled (analytical design model), simulated (ADS simulation tool) and measured results are in good correlation. Relying on the proposed theoretical, numerical and experimental models, the BP NGD behaviour is validated successfully with GD responses specified by the NGD centre frequency: it is observed around 2.35 GHz, with an NGD value of about −2 ns. Research limitations/implications: It is to be noticed the proposed GD analysis requires limitations of the theoretical NGD model. It is depicted and validated through a POC demonstrating that the circuit presents a possibility to generate NGD function around certain frequencies (assuming constraints around usable frequency and bandwidth). Practical implications: The NGD O-shape topology developed in this work could be exploited in the future in the microwave and radiofrequency context. Thus, it is expected to develop GD equalization technique for radiofrequency and microwave filters, GD compensation of oscillators, filters and communication systems, design of broadband switch-less bi-directional amplifiers, efficient enhancement of feedforward amplifiers, design method of frequency independent phase shifters with negligible delay, synthesis method of arbitrary-angle beamforming antennas. The BP NGD behavior may also be successfully used for the reduction of resonance effect for the electronic compatibility (EMC) of electronic devices. Social implications: The non-conventional NGD O-circuit theoretical development and validation through experimental POC could be exploited by academic and industrial developers in the area of wireless communications including, but not restricted to, 5-generation communication systems. The use of the remarkable NGD effect is also useful for the mitigation of electromagnetic interferences between electronic devices and more and more complex electromagnetic environment (current development of Internet of Things[ IoT]). Originality/value: The originality of this work relies on the new NGD design proposed in this work including the extraction of S-matrix parameters of the microstrip novel structure designed. The validation process based upon an experimental POC showed very interesting levels of NGD O-circuit (nanosecond-GD duration). [ABSTRACT FROM AUTHOR]

Dense urban development on a hilly terrain coupled with intense seasonal rainfall and heterogeneous weathering profiles give rise to acute debris-flow problems in Hong Kong. The Geotechnical Engineering Office (GEO) of the Hong Kong SAR Government has launched a holistic research and development (R&D) programme and collaborated with various tertiary institutes and professional bodies to support the development of a comprehensive technical framework for managing landslide risk and designing debris-flow mitigation measures. The scope of the technical development work includes compilation of landslide inventories, field studies of debris flows, development and calibration of tools for landslide run-out modelling, back analysis of notable debris flows, physical and numerical modelling of the interaction between debris flows and mitigation measures, formulation of a technical framework for evaluating debris-flow hazards, and development of pragmatic mitigation strategies and design methodologies for debris-flow countermeasures. The work has advanced the technical understanding of debris-flow hazards and transformed the natural terrain landslide risk management practice in Hong Kong. New analytical tools and improved design methodologies are being applied in routine geotechnical engineering practice. [ABSTRACT FROM AUTHOR]

Purpose: This paper has two parts, namely, Part 1 and Part 2. The purpose of this paper (Part 1) is to explain an adaptive relational paradigm that can efficaciously respond to the complex issues in wicked problems. A relational paradigm can work across the disciplines and fields that characterise wicked problems. It is also methodologically plural – that is it uses various inquiry instruments together. It becomes a hybrid approach when involving narratives and structured processes enabling the adopted instruments to converge to a coherent (living) story. The purpose of Part 2 will be to provide a theoretical framework that with illustration responds to Part 1. Design/methodology/approach: Wicked problems and their issues do not respect academic disciplines, and as they are multidisciplinary, they require a cross-disciplinary approach when seeking resolution. Autonomous agency theory is adopted capable of structuring cross-disciplinary inquiry processes and formulating a hybrid inquiry paradigm. The paper sets up a narrative agency approachable of delivering a structure that results in a general theory of hybrid inquiry. Findings: The paradigm, which traditionally defines a field of study conceptualises and regulates approaches that enable inquiry into behavioural systems. Mono-disciplinary, they are not suitable for the resolution of issues that arise from cross-disciplinary wicked problems. To resolve this, a relational paradigm has been defined within which sits a cross-disciplinary hybrid inquiry system. A general theory of hybrid inquiry has been offered. It is shown that agency theory can successfully embrace a relational paradigm. Research limitations/implications: To determine the limitations of this theory there is a need to provide exemplars, which is currently premature. Another outcome is to centre on modes of practice in hybrid inquiry, but there is insufficient space for this here. Originality/value: This paper makes an original contribution by formulating a structured approach on the creation of a relational paradigm capable of supporting hybrid inquiry. It also adopts cross-disciplinary theory to make its case for a relational paradigm, recognising that wicked problems are cross-disciplinary. As part of the regulatory process, it connects Rittel's IBIS schema intended to resolve wicked problems issues and the Johari Window and explains how they would relate. A means is suggested for determining the degree of undecidability of wicked problems issues, and hence, that of the models that inquiry produces. This uses formative characteristics that define a modelling space. The paper also adopts Husserl's concept or lifeworld, which acts as a channel for complex narrative theory through which regulative processes are enabled. [ABSTRACT FROM AUTHOR]

Modelling temperature- and composition-dependent thermal conductivity in alloys is challengeable and is seldom studied systematically. In the present work, a new model is developed to describe the temperature and concentration dependence of thermal conductivity for binary alloys. In this new model, firstly thermal conductivity of pure metals was modelled as the function of temperature for each phase and each magnetic state by the corresponding physically sound model. Secondly, in order to describe the composition and temperature dependence of thermal conductivity for solid phases, the combination of the theories of Nordheim and Mott for electric conductivity of alloys with the Wiedemann-Franz law was performed. Thirdly, the reliability of the new model was verified by presently measured thermal conductivities for pure Co, Ni and Co-Ni alloys at 300, 600, 900 and 1100 K as well as for binary Al-Zn, Mg-Zn and U-Zr systems using the data taken from the literature. The calculated thermal conductivities can well reproduce the measured ones in one-phase regions of a series of Co-Ni alloys. The thermal conductivity in a two-phase region of the Co-Ni system is reasonably predicted as well. It is demonstrated that the new model can be utilized to evaluate the thermal conductivity over the whole investigated composition and temperature ranges for the first time and is expected to be extended to ternary and multicomponent systems by CALPHAD method, which contributes significantly to the development of computational design of materials. [ABSTRACT FROM AUTHOR]

In modelling and simulation a user performs complex sequences of tasks that are intrinsically linked in the form of networks. Tasks include simpler steps such as copying and transforming files to using mesh generation or visualisation software to create inputs or to analyse outputs. Typically, these sequences involve manual steps which are time expensive, often involve use of multiple, incompatible software tools of various levels of usability, which are usually not well documented, and so create significant challenges for provenance, reproducibility and transfer to other users. These semi-manual workflows also inhibit sharing of capabilities and commercialisation. This paper explores how the adoption of the scientific workflow system Workspace can significantly improve such research and engineering activities by streamlining and automating the workflows involved. Benefits ensue in terms of improved collaboration through the sharing of workflow components, higher productivity, reduced costs and shorter development cycles through the reuse of software components and workflows and a reduction in risk due to improved reproducibility, documentation and provenance. The use of the Workspace platform allows such workflows to be executed via an interactive GUI, in batch mode via the command prompt, or embedded within self-contained applications. These applications can take the form of closed source binaries, web services or 'software as a service' applications. This supports significantly improved translation of research prototype software to end users and creates low cost pathways for commercialisation. [ABSTRACT FROM AUTHOR]

Uncertainty in model-based decision support is commonly addressed using mixed methods rather than a single method. Different mixes of methods result in different modelling and processes for robust decision support, and subsequently different decision outcomes. This article focuses on the notion of 'good' modelling practice and develops a reporting guideline to make the use of multiple methods in robust decision support transparent. The guideline raises awareness about the characteristics of methodological and mixing design choices made throughout the modelling process. While not intending to be universally applicable, the guideline represents a move towards the development of universal standards to promote the generalisability, reproducibility, and comparability of different practices of robust decision support and to improve the recognition of the values of specific robust decision support frameworks. The article demonstrates the process for the use of mixed methods in an illustrative case in asset life cycle planning. The case study explains choices made at each step of this mixing process and presents justifications for the choices made, using the suggested guideline. The illustrative case also demonstrates generated decision insights resulted from the choices made. • The use of multiple methods is popular in model-based decision support. • Modeller methodological and mixing design choices lead to different decision outcomes. • The clarification of choices supports a 'good' modelling practice in decision support. • We develop a guideline to clarify methodological and mixing design choices in robust decision support. [ABSTRACT FROM AUTHOR]

Alveolar echinococcosis (AE) is a zoonotic parasitic diseases caused by a cestode parasite known as Echinococcus multilocularis. The parasite has a wildlife cycle with definitive hosts (foxes) and small mammals as intermediate hosts (rodents) while humans are the accidental hosts. Parasite infection pressure relation to time of the year and age dependent infection pressure for parasite abundance also depend on the urbanization. The aim of current work is forecasting the thresholds via the computational analysis of the disease spread which is a useful approach since it can help to design the experimental settings with better planning and efficiency. Network analysis when interlinked with the computational techniques provides better insight into the spatial and temporal heterogeneities. In the present study, a mathematical framework that describes the transmission dynamics and control measures of E. multilocularis in foxes is documented. We used treatment of foxes with baits for the prevention of the E. multilocularis infection. A novel approach of networking, called Petri net (PN), based on density dependent differential equations, is utilized during this research. The accurate description of the transmission of the parasite and the effect of drug on it is provided to the readers in this article. The transitions, which are difficult to analyse theoretically, are presented with the aid of the discrete approach of networking. A discrete mathematical framework can prove to be an accurate and robust tool to analyse and control the parasite dynamics. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the pricing strategies of an online trading platform with indirect network externalities by considering heterogeneous trading behavior in the downstream market and the long tail. Design/methodology/approach: The game theory, optimization and comparative static are used in this research. The equilibria are derived from the game theory, and with them, the authors optimize the platform's profit function. Comparative static is used to study pricing strategies. Findings: It is found that with heterogeneous trading behavior, the transaction-based model is more profitable than the subscription-based model by reason of the feasibility of "price discrimination". However, with certain advantages of subscription fees such as avoiding offline transactions, the subscription-based model is better with a concentrated distribution of sellers' revenues (the Gini coefficient is small). With a lucrative long tail, the platform should set a low price to attract small sellers in the long tail. Besides, if the Gini coefficient is large, the effects of the market entry barrier of sellers on the optimal price in each model may be opposite. Research limitations/implications: It implies that the choice of revenue models and pricing strategies are influenced by the Gini coefficient or the long tail. The exogenous setting in which buyers can use the platform for free needs further extension. Practical implications: The authors provide insights on how to choose revenue models and how to price the sellers with the long tail phenomenon. Originality/value: This paper emphasizes the role of the long tail on pricing strategies and the effect of heterogeneous trading behavior on model selection. [ABSTRACT FROM AUTHOR]

A recent study conducted at the University of Arkansas explores the use of discrete-event simulation to optimize staff allocation and patient flow in a pediatric hospital setting. The researchers developed a simulation model based on historical patient data to analyze the entire patient journey from clinic visits to surgery. Using machine learning, the model was optimized to minimize patient wait times by allocating physician resources more effectively. The study provides valuable insights into improving the overall patient experience in hospitals. [Extracted from the article]

Purpose: The purpose of this paper is to obtain an accurate methodology for modelling and analysis of the permanent magnet synchronous generator connected to power electronic components. Design/methodology/approach: This paper presents the methodology of the co-simulation of a permanent magnet synchronous generator. It combines Simulink, Maxwell and Simplorer software to demonstrate the electrical machine behaviour connected with the power electronics' circuit. The finite element analysis performed on the designed machine exhibit a more accurate behaviour over simplified Simulink models. Results between both simulation and co-simulation are compared to measurements. Findings: The co-simulation approach offers a more accurate depiction of the machine behaviour and its interaction with the non-linear circuits. Research limitations/implications: This paper focuses on the interior permanent magnet type of PMSG and its interaction with a passive rectifier (nonlinear circuit). Practical implications: The advanced capabilities of the co-simulation method allow to analyse more variations (geometry, materials, etc.), and its interaction with non-linear circuits, than previous simulation techniques. Originality/value: The co-simulation as a tool for analysis and design of systems interconnected with unconventional and conventional electrical machines and prototypes, and the comparison of the obtained results with classical analysis and design methods, against measurements obtained from the prototype. [ABSTRACT FROM AUTHOR]

The aerodynamic levitation provides an efficient technique for the research on thermophysical properties and solidification behavior of refractory materials. However, there is a nonnegligible temperature differences across sample, causing unexpected uncertainty of measurement, such as, thermal expansivity and undercooling limit. We establish thermal filed model with properly simplified boundary condition, and derive quantitative expressions of this ambiguous temperature difference. Here we show that the temperature difference not only related to the average temperature, relative size and thermal conductivity of sample, but significantly influenced by the rotation pattern of sample. A huge temperature differences is almost inevitable when the sample with low thermal conductivity and high melting point is smelted in stationary suspension pattern, however, a drastically reduction of temperature difference can be fulfilled by simply making the sample rotation in up to down pattern. The thermal filed simulation was used to confirm the validity of these theoretical expressions. This work shed light on temperature difference in aerodynamic levitation. Based on this work, one can simply estimate the extent of temperature difference across the sample, and regulated that conveniently if needed, which benefit for novel material preparation and solidification mechanism study based on this technique. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to examine the effect of varying compaction pressure on magnetic properties of self-developed soft magnetic composite (SMC) cores. The change in shape of ferromagnetic hysteresis curves has – in turn – the impact on the values of hysteresis model parameters. The phenomenological GRUCAD model is chosen for description of hysteresis curves. Design/methodology/approach: Several cylinder-shaped cores have been made from a mixture of iron powder and suspense polyvinyl chloride using a hydraulic press with a form and a band with a thermocouple for controlling heat treatment conditions. The only varying parameter in the study is the compaction pressure. The magnetic properties of developed cores have been measured using a computer-acquisition card and LabView software. The obtained hysteresis curves are fitted to the equations of the phenomenological GRUCAD model. This description is compliant with the laws of irreversible thermodynamics. The variations of model parameters are presented as functions of compacting pressure. Findings: The compaction pressure has a significant impact on magnetic properties of self-developed SMC cores. The paper provides a number of charts useful for checking how the parameters of the hysteresis model are affected. Research limitations/implications: The present paper is limited to modelling symmetrical loops only. Description of more complex magnetization cycles is postponed to another, forthcoming paper. Practical implications: The GRUCAD hysteresis model may be a useful tool for the designers of magnetic circuits. Its parameters depend on the processing conditions (in this study – the compaction pressure) of the SMC cores. Originality/value: Modelling of magnetic properties of SMC cores has been carried so far using some well-known description like Preisach, Takács and Jiles–Atherton proposals. The GRUCAD model has a number of advantages, and it may be a useful alternative to the latter formalism. So far it has been used for description of hysteresis curves in conventional materials like non-oriented and grain-oriented electrical steels. In the present work, it is applied to novel SMC materials. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study is to investigate the possibility of soft science measurement of motivation under strict hard science criteria from observations of individual animals and to suggest the conditions under which an observation can be classified as a measurement.Design/methodology/approach The methodology starts from reconciling second-order cybernetics/radical constructivism (SOC/RC) understanding of the central role of the observer with physical measurements, which accepts the existence of a mind-independent reality. As a result of the reconciliation, parallels were identified between the SOC/RC experiences of as_is and as_if, on the one hand, and the measurement concepts of accuracy and resolution, on the other hand. The scales of physical measurement are defined by criteria of varying strictness, and the scales that meet the strict criterion of concatenation are generally considered hard science and lead to well-defined accuracy and precision. The similarity between SOC/RC and physical measurement suggests that if accuracy and precision can be computed from observations, then the observations can be classified as measurements in a strict hard science fashion; otherwise, the observations are just observations.Findings A nonlinear dynamic model of motivation is reintroduced as an example for reference in measurements of motivation. If there was an agreement on its use among observers (Ethologists), which in reality is not the case, then empirical data may be collected, and the averages and spreads of parameter estimations will define a reference for an animal species. Later, observers with their own data will calibrate with the reference model, so that new observers will have calculated values of accuracy and precision for their data.Research limitations/implications Unlike hard science whose scales of measurement are practically unambiguous, measuring the purpose of behaviour of an animal has inherent ambiguity according to the reintroduced model. The ambiguity cannot be resolved from instantaneous readings. The necessary existence of ambiguity renders the criticism of hard science invalid, that of expecting to measure motivation with a static scale as if it were temperature.Practical implications Human observers can be treated as measuring devices of motivation from observing behaviour. Each observer can have characteristic accuracy/precision, or validity/reliability, calculated from empirical data.Social implications This is an inductive, rather than deductive, study of individual animal behaviour; the author believes it is extensible to individual human behaviour and personality studies. However, group behaviour studies are beyond its scope.Originality/value The author believes that the suggestion of ambiguity of scales of animal motivation is original, and the suggested link between SOC/RC and a mainstream hard science is new. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to focus on usage of Al2O3/water nanofluid as working fluid in a combi boiler. The plate heat exchanger located at the bottom of the combi boiler has been used for heating the domestic water in the present study. Al2O3/water nanofluid has also been used in obtaining of the heat energy provided from combustion. Therefore, thermal performance of Al2O3/water has been determined by comparing water and nanofluid-water mixture. The present study also investigates heat transfer rates as numerical and experimental for varying cold side outlet temperatures, comparatively. Design/methodology/approach: The present study has included both experimental and numerical methodologies. The experimental setup consists of main heat exchanger, atmospheric burner, circulation pump and plate-type heat exchanger in which the Al2O3/water nanofluid was used as working fluid to heat the domestic water. In the numerical part of the study, a commercial computational fluid dynamic code has been used to model heat rate and thermal efficiency of the heat exchanger used. Findings: It has been concluded that the predicted results are in satisfactorily good agreement with the measured data. In the experimental part of the study, the flow rate of Al2O3/water nanofluid was kept constant during the experiments. The flow rates of the water by which the heated Al2O3/water nanofluid mixture was cooled via the plate heat exchanger have been changed as 3, 4, 5 and 6 lpm. The domestic water temperatures that were kept constant have also been changed as 40°C, 45°C, 50°C, 55°C and 60°C. It has been concluded that the Al2O3/water nanofluid thermal efficiency has been 16 per cent better than pure water. Originality/value: The main originality of the present study is that thermal efficiency of the plate-type heat exchanger when Al2O3/water mixture nanofluids are used as there are limited studies related to the usage of Al2O3/water mixture nanofluids in the plate-type heat exchanger not only experimental but also numerical methodologies. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, fuel cells are regarded as a promising solution in the context of development of a "More Electrical Aircraft". Indeed, the integration of fuel cell systems in aircraft allows generating electrical energy with high efficiency and low environmental impact. However, there are still many questions about the functioning and the performance of these systems in typical aeronautical conditions. The present work is focused on aeronautical conditions linked to cabin applications. Therefore, a particular attention is paid to low pressure operation, with experimental investigations carried out at subatmospheric pressures. Given the complexity of the possible interactions, an experimental database was created using the Design of Experiments method. The experimental results are first presented and discussed, then exploited via a modelling approach. The objective is to define a model for the polarization curve able to describe its evolution when the operating conditions change. The methodology used to construct the model is introduced step-by-step as well as the modelling results for the various involved phenomena. At the end, the predictive behaviour of the model is investigated with polarization curves carried out at operating conditions taken outside the definition range of the DoE. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to present how to use the difference equations for analysis of flyback converter circuit.Design/methodology/approach Switching circuits have variable structural topologies. In every switched-mode, they have different dynamics and different equations. First, the exact equivalent circuit of flyback converter, then, set of difference equations are obtained. The flyback converter has a nonlinear structure; however, the presented technique allows the circuit equations to be linear. The transient-state and steady-state analysis of flyback converter, one of popular switching circuits, are carried out by using difference-equations.Findings The proposed analysis method does not contain any numerical approximation and the results are in the form of exact solution. Another superiority of the method is that the desired instantaneous values can be obtained directly, the simulation does not need to be started from the beginning. Numerical results agree well with the theoretical results of flyback converter. The simulation results obtained by using the proposed method and Matlab-based results are compared.Originality/value This paper contributes a different mathematical background for analysis of switching converters to the literature. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to deal with a modified-based approach for the evaluation of the steady state performances of three-phase self-excited induction generator (SEIG) feeding single-phase load.Design/methodology/approach Using the symmetrical components method, the proposed approach is based on a modified model of unbalanced three-phase SEIG, which is formulated similarly to the well-known model of balanced three-phase SEIG. Owing to this modified model, the determination of the SEIG operating point amounts to the resolution of two semi-decoupled nonlinear equations for two unknowns; the magnetizing reactance and the per-unit frequency. A simple resolution method based on an iterative two-step technique is used. The results obtained by the proposed approach are compared with those given by a conventional approach and are validated experimentally.Findings The proposed approach is as accurate as the conventional approach. Further, for the same accuracy degree, the proposed approach permits to speed up the resolution when compared to the conventional approach, as only few iterations are required for the convergence. The proposed approach was also successfully used for the steady state analysis of SEIG under generalized unbalanced loading conditions.Practical implications The determination of the operating point of the generator is based on a modified model of the generator and a simple iterative resolution method. The calculation technique can be implemented on low resource controller to provide online voltage control of the SEIG.Originality/value The paper contains two main originalities. The first one consists in a modified formulation of the SEIG model under unbalanced loading conditions. The modified formulation permits the use of the well-known model of balanced three-phase SEIG. Unlike previous ones reported in the literature, the proposed model does not require tedious algebraic manipulations. The second originality is the use of two-step technique to solve the equations, which permits to avoid laborious mathematical derivations and manipulating high-order polynomials. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to describe a semi-analytical modeling technique to predict eddy currents in three-dimensional (3D) conducting structures with finite dimensions. Using the developed method, power losses and parasitic forces that result from eddy current distributions can be computed.Design/methodology/approach In conducting regions, the Fourier-based solutions are developed to include a spatially dependent conductivity in the expressions of electromagnetic quantities. To validate the method, it is applied to an electromagnetic configuration and the results are compared to finite element results.Findings The method shows good agreement with the finite element method for a large range of frequencies. The convergence of the presented model is analyzed.Research limitations/implications Because of the Fourier series basis of the solution, the results depend on the considered number of harmonics. When conducting structures are small with respect to the spatial period, the number of harmonics has to be relatively large.Practical implications Because of the general form of the solutions, the technique can be applied to a wide range of electromagnetic configurations to predict, e.g. eddy current losses in magnets or wireless energy transfer systems. By adaptation of the conductivity function in conducting regions, eddy current distributions in structures containing holes or slit patterns can be obtained.Originality/value With the presented technique, eddy currents in conducting structures of finite dimensions can be modeled. The semi-analytical model is for a relatively low number of harmonics computationally faster than 3D finite element methods. The method has been validated and shown to be computationally accurate. [ABSTRACT FROM AUTHOR]

Highlights • N photobioreactors in series modelled with 3N ODEs having Monod and Droop kinetics. • State variables: concentrations of algea and substrate, and internal cell quota. • Results: existence, uniqueness, stability and conditions for steady states. Abstract A photobioreactor (PBR) contains microalgae which under illumination consume carbon dioxide and substrate dissolved in water, and produce oxygen. The process is used in water recovery resource facilities with a continuous flow of wastewaster through the PBR. With several PBRs in series the reduction of substrate can be improved. This paper contains a thorough analysis of a model of PBRs in series, where each PBR is modelled with a system of three ordinary differential equations for the concentrations of dissolved substrate and biomass (algae), and the internal cell quota of substrate to biomass. Each PBR has a certain volume and irradiation. The absorption rate of substrate into the cells is modelled with Monod kinetics, whereas the biomass growth rate is modelled with Droop kinetics, in which both a minimum and a maximum internal cell quota are assumed. The main result is that the model has a unique stable steady-state solution with algae in all PBRs. Another stable steady-state solution is the wash-out solution with no algae in the system. Other steady-state solutions are combinations of these two with no algae in some of the first PBRs and algae in the rest of the PBRs in the series. Conditions on the illumination, volumetric flow and volumes of the PBRs are given for the respective solution. Numerical solutions illustrate the theoretical results and indicate further properties. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to introduce and illustrate a computational technique capable of determining the geometry and complex permittivity of a supplementary dielectric insert making distributions of microwave-induced dissipated power within the processed material as uniform as possible.Design/methodology/approach The proposed technique is based on a 3D electromagnetic model of the cavity containing both the processed material and the insert. Optimization problem is formulated for design variables (geometrical and material parameters of the insert) identified from computational tests and an objective function (the relative standard deviation [RSD]) introduced as a metric of the field uniformity. Numerical inversion is performed with the method of sequential quadratic programming.Findings Functionality of the procedure is illustrated by synthesis of a dielectric insert in an applicator for microwave fixation. Optimization is completed for four design variables (two geometrical parameters, dielectric constant and the loss factor of the insert) with 1,000 points in the database. The best three optimal solutions provide RSD approximately 20 per cent, whereas for the patterns corresponding to all 1,000 non-optimized (randomly chosen) sets of design variables this metric is in the interval from 27 to 136 per cent with the average of 78 per cent.Research limitations/implications As microwave thermal processing is intrinsically inhomogeneous and the heating time is not a part of the underlying model, the procedure is able to lead only to a certain degree of closeness to uniformity and is intended for applications with high heating rates. The initial phase of computational identification of design variables and their bounds is therefore very important and may pre-condition the “quality” of the optimal solution. The technique may work more efficiently in combination with advanced optimization techniques dealing with “smart” (rather than random) generation of the data; for the use with more general microwave heating processes characterized by lower heating rates, the technique has to use the metric of non-uniformity involving temperature and heating time.Practical implications While the procedure can be used for computer-aided design (CAD) of microwave applicators, a related practical limitation may emerge from the fact that the material with particular complex permittivity (determined in the course of optimization) may not exist. In such cases, the procedure can be rerun for the constant values of material parameters of the available medium mostly close to the optimal ones to tune geometrical parameters of the insert. Special manufacturing techniques capable of producing a material with required complex permittivity also may be a practical option here.Originality/value Non-uniformity of microwave heating remains a key challenge in the design of many practical applicators. This paper suggests a concept of a practical CAD and outlines corresponding computational procedure that could be used for designing a range of applied systems with high heating rates. [ABSTRACT FROM AUTHOR]

Purpose The microwave heating technique can be used in the production of iron for productivity improvement when the consumption of low-quality iron ore increases. Iron-containing dust agglomerates are an important source of iron; however, the crushing strength of raw agglomerates is low, which decreases the yield owing to breaking. Therefore, they need to be dried using a “band dryer” to reduce the amount of excess water and improve their crushing strength. This paper aims to present the structure of an antenna that efficiently provides microwave energy to the agglomerate layer inside the band dryer.Design/methodology/approach Electromagnetic field analysis and experiments that simulate inside the band dryer were performed to evaluate the radiation efficiency of the slot antenna for microwave heating of the agglomerate layer in the presence of a metal conveyor.Findings The results show that slot height should be larger than the antenna position from the metal conveyor and smaller than the sum of the antenna position and quarter of the guide wavelength, to maximize the radiation efficiency of the antenna. By satisfying this condition, the radiation efficiency was higher than 75 per cent in the experiments.Originality/value This paper presents for the first time the optimum relation between slot height and antenna position to apply the microwave heating technique to iron-containing agglomerates in a band dryer. [ABSTRACT FROM AUTHOR]

Purpose The purpose of the paper is to present three different contributions to a general model theory which the authors think as relevant to systems research based on systems theory, cybernetics and constructivism. This also implies that the three contributions are shown to be of use both in the study of systems that operate by models, as well as in the practice of designing models.Design/methodology/approach The text is conceptual and mainly of a descriptive and referring character. Besides the sections on the three contributions to a model theory, the authors have inserted sections that relate them to systems theory. This is also achieved by the help of some simple models.Findings The paper also points to models as important instruments in constructing and selecting information to observing systems, and the authors hope that the text can be helpful in developing better knowledge of how models work.Originality/value The text is about observing systems that observe by models, and that is probably a somewhat new perspective. It is hoped that the paper can be inspiring to further studies on this matter. [ABSTRACT FROM AUTHOR]

Purpose A novel technique for control of complex physical processes based on the solution of their sufficiently accurate models is presented. The technique works with the model order reduction (MOR), which significantly accelerates the solution at a still acceptable uncertainty. Its advantages are illustrated with an example of induction brazing.Design/methodology/approach The complete mathematical model of the above heat treatment process is presented. Considering all relevant nonlinearities, the numerical model is reduced using the orthogonal decomposition and solved by the finite element method (FEM). It is cheap compared with classical FEM.Findings The proposed technique is applicable in a wide variety of linear and weakly nonlinear problems and exhibits a good degree of robustness and reliability.Research limitations/implications The quality of obtained results strongly depends on the temperature dependencies of material properties and degree of nonlinearities involved. In case of multiphysics problems characterized by low nonlinearities, the results of solved problems differ only negligibly from those solved on the full model, but the computation time is lower by two and more orders. Yet, however, application of the technique in problems with stronger nonlinearities was not fully evaluated.Practical implications The presented model and methodology of its solution may represent a basis for design of complex technologies connected with induction-based heat treatment of metal materials.Originality/value Proposal of a sophisticated methodology for solution of complex multiphysics problems established the MOR technology that significantly accelerates their solution at still acceptable errors. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to provide a flexible model for a system of inductively coupled loops in a quasi-static magnetic field. The outlined model is used for theoretical analyses on the magnetic field-based football goal detection system called as GoalRef, where a primary loop generates a magnetic field around the goal. The passive loops are integrated in the football, and a goal is deduced from induced voltages in loop antennas mounted on the goal frame.Design/methodology/approach Based on the law of Biot–Savart, the magnetic vector potential of a primary current loop is calculated. The induced voltages in secondary loops are derived by Faraday’s Law. Expressions to calculate induced voltages in elliptically shaped loops and their magnetic field are also presented.Findings The induced voltages in secondary loops close to the primary loop are derived by either numerically integrating the primary magnetic flux density over the area of the secondary loop or by integrating the primary magnetic vector potential over the boundary of that loop. Both approaches are examined and compared with respect to accuracy and calculation time. It is shown that using the magnetic vector potential instead of the magnetic flux density can decrease the processing time by a factor of around 100.Research limitations/implications Environmental influences like conductive or permeable obstacles are not considered in the model.Practical implications The model can be used to investigate the theoretical behavior of inductively coupled systems.Originality/value The proposed model provides a flexible, fast and accurate tool for calculations of inductively coupled systems, where the loops can have arbitrary shape, position and orientation. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to present an analytical way of formulating the vital parameters of an equivalent hysteresis loop of a composite, multi-component magnetic substance. By using the hyperbolic model, the only model, which separates the constituent parts of the composite magnetic materials, an equivalent loop can be composed analytically. So far, it was only possible to superimpose the tanh functions by numerical method. With this transformation, all multi-component composite substances can be treated mathematically as a single-phase material, as in the T(x) model, and include it in mathematical operations. The transformation works with good accuracy for major and minor loops and provides an easy analytical way to arrive to the vital parameters. This also shows an analytical way to the easy solution of some of the difficult problems in magnetism for multi-component ferrous materials, such as Fourier and Laplace transforms, accommodation and energy loss, already solved for the T(x) model.Design/methodology/approach The mathematical single loop formulation of hysteresis loop of a multi-phase substance shows the way in good approximation of the sum of constituent loops, described by tanh functions. That was so far only possible by numerical methods. By doing so, it becomes equivalent to the T(x) model for mathematical operations.Findings The described method gives an analytical formulation [identical to the T(x) model] of multi-component hysteresis loops described by hyperbolic model, leading to simple solution of difficult problems in magnetism such as loop reversal.Research limitations/implications Although the method is an approximation, its accuracy is good enough for use in magnetic research and practical applications in industries engaged in application of magnetic materials.Practical implications The hyperbolic model is the only one which separates the magnetic substance, used in practice, to constituent components by describing its multi-component state. Superimposing the components was only possible so far by numerical means. The transformation shown is an analytical approximation applicable in mathematical calculations. The transformation described here enables the user to apply all rules applicable to the T(x) model.Social implications This study equally helps researchers and practical users of the hyperbolic model.Originality/value This novel analytical approach to the problem provides an acceptable mathematical solution for practical problems in research and manufacturing. It shows a way to solutions of many difficult problems in magnetism. [ABSTRACT FROM AUTHOR]

Analysis of big data is a hot topic, but the first problem encountered by many statisticians is ‘where to start’. We would like to share our story with the readers who have less experience in this area, and hopefully it can shed some light on it. [ABSTRACT FROM AUTHOR]

Purpose Static converters generate current harmonics in power grids. For numerous studies, analytical frequency modeling is preferred to carry out their harmonic modeling in the context of sizing by optimization. However, a design by optimization has to consider other constraints, e.g. modeling constraints and operating constraints. In this way, this paper aims to focus on applying an analytical frequency modeling on the sizing by optimization of an aircraft electrical power channel.Design/methodology/approach The paper aims to size a multiphysical system by optimization. In this way, the sizing of an aircraft electrical power channel by optimization has been carried out. The models of all the channel components are analytical. Specifically, the frequency model of the power electronics is based on Tran et al. (2016) and is made of equalities and inequalities. Due to this modeling choice, the optimization satisfies hundreds of constraints, such as modeling constraints and static converter operating constraints. Furthermore, transient constraints are only verified after optimization.Findings The difficulty is the modeling of the system by taking into account nonlinear implicit equations having several solutions. A solution is the addition of inequality constraints to the model to guide the implicit solving. Furthermore, this greatly helps the optimization algorithm to find the good operating mode of the static converter, at steady state. This aspect is indispensable to validate the sizing model.Research limitations/implications The number of the configurations per operating period of the static converters is defined a priori and limited.Originality/value The analytical model for the sizing is formulated as a constrained optimization problem. Its solving and the sizing by optimization are carried out by the same optimization algorithm. [ABSTRACT FROM AUTHOR]

Purpose Literature is unanimous about the effects of functional diversity in new product development teams. This paper uses simulation modeling to investigate the contradictory and dynamic effects of functional team diversity on innovation revealed by empirical literature. This paper aims to start a discussion on this dynamic perspective of team diversity.Design/methodology/approach This paper presents a systemic approach toward investigating the contradictory and dynamic effects of functional team diversity on innovation by creating a simplified System Dynamics model of functional diversity in new product development teams.Findings Although the simulation model is highly simplified, it can integrate the contradictory results of empirical data and the dynamic component of teamwork. Therefore, it offers a new approach to investigating the effects of functional diversity on team innovation.Research limitations/implications The model is highly simplified and exemplary. No actual data are included, thus limiting the results as fully theoretical.Originality/value Empirical studies often analyze the effects of functional diversity on innovation in new product development teams. However, empirical data are unclear regarding the nature of the effects of functional diversity on innovation. Therefore, functional diversity is chosen for the simulation model as being the most controversially discussed diversity attribute. By applying a simulation model to the problem and adding a dynamic component to teamwork, we are contributing to the explanation for the contradictory findings in literature. [ABSTRACT FROM AUTHOR]

Purpose The holistic numerical model based on cellular automata (CA) and lattice Boltzmann method (LBM) are being developed as part of an integrated modelling approach applied to study the interaction of different physical mechanisms in laser-assisted additive layer manufacturing (ALM) of orthopaedic implants. Several physical events occurring in sequence or simultaneously are considered in the holistic model. They include a powder bed deposition, laser energy absorption and heating of the powder bed by the moving laser beam, leading to powder melting or sintering, fluid flow in the melted pool and flow through partly or not melted material, and solidification. The purpose of this study is to develop a structure of the holistic numerical model based on CA and LBM applicable for studying the interaction of the different physical mechanisms in ALM of orthopaedic implants. The model supposed to be compatible with the earlier developed CA-based model for the generation of the powder bed.Design/methodology/approach The mentioned physical events are accompanied by heat transfer in solid and liquid phases including interface heat transfer at the boundaries. The sintering/melting model is being developed using LBM as an independent numerical method for hydrodynamic simulations originated from lattice gas cellular automata. It is going to be coupled with the CA-based model of powder bed generation.Findings The entire laser-assisted ALM process has been analysed and divided on several stages considering the relevant physical phenomena. The entire holistic model consisting of four interrelated submodels has currently been developed to a different extent. The submodels include the CA-based model of powder bed generation, the LBM-CA-based model of heat exchange and transfer, the thermal solid-liquid interface model and the mechanical solid-liquid interface model for continuous liquid flow.Practical implications The results obtained can be used to explain the interaction of the different physical mechanisms in ALM, which is an intensively developing field of advanced manufacturing of metal, non-metal and composite structural parts, for instance, in bio-engineering. The proposed holistic model is considered to be a part of the integrated modelling approach being developed as a numerical tool for investigation of the co-operative relationships between multiphysical phenomena occurring in sequence or simultaneously during heating of the powder bed by the moving high energy heat source, leading to selective powder sintering or melting, fluid flow in the melted pool and through partly (or not) melted material, as well as solidification. The model is compatible with the earlier developed CA-based model for the generation of the powder bed, allowing for decrease in the numerical noise.Originality/value The present results are original and new for the study of the complex relationships between multiphysical phenomena occurring during ALM process based on selective laser sintering or melting, including fluid flow and heat transfer, identified as crucial for obtaining the desirable properties. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to first present the key features of the fuzzy logic (FL) approach as a cost-effective technique in simulations of complex systems and then demonstrate the formulation and application of the method.Design/methodology/approach The FL approach is used as an alternative method of data handling, considering the complexity of analytical and numerical procedures and high costs of empirical experiments. The distance from gas distributor, the temperature and the voidage of the bed, flue gas velocity and the load of the boiler are the input parameters, whereas the overall heat transfer coefficient for the membrane walls constitutes the output. Five overlapping sigmoid and constant linguistic terms are used to describe the input and the output data, respectively. The Takagi–Sugeno inference engine and the weighted average defuzzification methods are applied to determine the fuzzy and crisp output value, respectively.Findings The performed FL model allows predicting the bed-to-wall heat transfer coefficient in a large-scale 670 t/h circulating fluidized bed (CFB) boiler. The local heat transfer coefficients evaluated using the developed model are in very good agreement with the data obtained in complementary investigations.Originality/value The performed model constitutes an easy-to-use and functional tool. The new approach can be helpful for further research on the bed-to-wall heat transfer coefficient in the CFB units. [ABSTRACT FROM AUTHOR]

Purpose This study aims to present a parametric model of a novel electrical machine, based on a slotless air gap winding, allowing for fast and precise magnetic circuit calculations.Design/methodology/approach Approximations of Fourier coefficients through an exponential function deliver the required nonlinear air gap flux density and inductance. Accordingly, major machine characteristics, such as back-EMF and torque, can be calculated analytically with high speed and precision. A physical model of the electrical machine with air gap windings is given. It is based on a finite element analysis of the air gap magnetic flux density and inductance. The air gap height and the permanent magnetic height are considered as magnetic circuit parameters.Findings In total, 11 Fourier coefficient matrixes with 65 sampling points each were generated. From each, matrix a two-dimensional surface function was approximated by using exponentials. Optimal parameters were calculated by the least-squares method. Comparison with the finite element model demonstrates a very low error of the analytical approximation for all Fourier coefficients considered. Finally, the dynamics of an electrical machine, modeled using the preceding magnetic flux density approximation, are analyzed in MATLAB Simulink. Required approximations of the phase self-inductance and mutual inductance were given. Accordingly, the effects of the two magnetic circuit parameters on the dynamics of electrical machine current as well as the electrical machine torque are explained.Originality/value The presented model offers high accuracy comparable to FE-models, needing only very limited computational complexity. [ABSTRACT FROM AUTHOR]

Purpose Modeling electric machines is one of the powerful approaches for analyzing their performance. A dynamic model and a steady-state model are introduced for each electric machine. Permanent magnet induction machine (PMIM) is a dual-rotor electric machine, which has various advantages such as high-power factor and low magnetizing current. Studying PMIM and its modeling might be valuable. The purpose of this paper is to introduce a simple and accurate method for dynamic and steady-state modeling of PMIM.Design/methodology/approach In this paper, arbitrary dqo reference frame is used to model PMIM. First, three-phase dynamic equations of stator and rotors are introduced. Then, they are transferred to an arbitrary reference frame. The voltage and magnetic flux equations aligned at dqo axes are obtained. These equations give the dynamic model. To investigate the results, PMIM simulation is performed according to obtained dynamic equations. Simulation results verify the analytic calculations.Findings In this paper, dynamic equations of PMIM are obtained. These equations are used to determine dynamic equivalent circuits of PMIM. Steady-state equations and one phase equivalent circuit of the PMIM using phasor relations are also extracted.Originality/value PMIM equations along dqo axes and their dynamic and steady-state equivalent circuits are determined. These equations and the equivalent circuits can be transformed to different reference frames and analyzed easily. [ABSTRACT FROM AUTHOR]

Fibre network materials constitute a class of highly porous materials with low density, promising for functional and structural applications; however, very limited research has been conducted, especially on simulation and analytical models. In this paper, a continuum mechanics-based three-dimensional periodic beam-network model has been constructed to describe the stochastic fibre network materials. In this model, the density of the cross-linkers is directly related to the relative density of the fibre network materials, and the cross-linkers are represented by equivalent beam elements. The objective of this work was to delineate the elasto-plastic behaviour of the stochastic fibre network materials. Characteristic stress and strain derived from the total strain energy density have been adopted to reveal the yielding behaviour of the fibre networks. The results indicate that the stochastic fibre network materials are transversely isotropic. The in-plane stiffness and strength are much larger than those in the out-of-plane direction. For the fibre network materials with a small relative density, the relationship between the uniaxial yield strength and the relative density is a quadratic function in the x direction and is a cubic function in the z direction, which agree well with our dimensional analysis and are consistent with the relevant experimental results in literature. The yield surface depends strongly on the relative density and the connection between fibres. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study is to propose a new dynamic model of a production-inventory control system. The objective of the new model is to maximise the flexibility of the system so that it can be used by decision makers to design inventory systems that adopt various strategies that provide a balance between reducing the bullwhip effect and improving the responsiveness of inventory performance.Design/methodology/approach The proposed production-inventory control system is modelled and analysed via control theory and simulations. The production-inventory feedback control system is modelled through continuous time differential equations. The simulation experiments design is conducted by using the state-space model of the system. The Automatic Pipeline Inventory and Order-Based Production Control System (APIOBPCS) model is used as a benchmark production-inventory control system.Findings The results showed that the Two Automatic Pipelines, Inventory and Order-Based Production Control System (2APIOBPCS) model outperforms APIOBPCS in terms of reducing the bullwhip effect. However, the 2APIOBPCS model has a negative impact on Customer Service Level. Therefore, with careful parameter setting, it is possible to design control decisions to be suitably responsive while generating smooth order patterns and obtain the best trade-off of the two objectives.Research limitations/implications This research is limited to the dynamics of single-echelon production-inventory control systems with zero desired inventory level.Originality/value This present model is an extension and improvement to Towill’s (1982) and John et al.’s (1994) work, since it presents a new dynamic model of a production-inventory control system which utilises an additional flow of information to improve the efficiency of order rate decisions. [ABSTRACT FROM AUTHOR]

A modelling suite for hydrogen transport during electrochemical permeation, degassing and thermal desorption spectroscopy is presented. The approach is based on Fick's diffusion laws, where the initial concentration and diffusion coefficients depend on microstructure and charging conditions. The evolution equations are shown to reduce to classical models for hydrogen diffusion and thermal desorption spectroscopy. The number density of trapping sites is found to be proportional to the mean spacing of each microstructural feature, including dislocations, grain boundaries and various precipitates. The model is validated with several steel grades and polycrystalline nickel for a wide range of processing conditions and microstructures. A systematic study of the factors affecting hydrogen mobility in martensitic steels showed that dislocations control the effective diffusion coefficient of hydrogen. However, they also release hydrogen into the lattice more rapidly than other kind of traps. It is suggested that these effects contribute to the increased susceptibility to hydrogen embrittlement in martensitic and other high-strength steels. These results show that the methodology can be employed as a tool for alloy and process design, and that dislocation kinematics play a crucial role in such design. [ABSTRACT FROM AUTHOR]

This work revisits the pharmacokinetic models derived from classical differential equations and proposes an extension to fractional differential equations to account for tissue trapping, which modifies the predicted drug concentration profiles. Unlike monotonic decay profiles, an oscillatory behaviour is often observed. The phenomenon may be the result of the recirculation of trapped drug molecules due to the heterogeneity of the tissue combined with the local action of the liver or other organs in depositing part of the drug for later release. The proposed model alleviates this limitation in data fitting profiles, without violating mass balance principles and physiological states. The paper also points to new concepts and techniques in modelling drug pharmacokinetic dynamics to account for short- and long-time recirculation effects. As such, it provides a better characterisation of unexplained secondary effects in patients undergoing treatment. It also establishes a link to unbounded drug accumulation models. [ABSTRACT FROM AUTHOR]

Purpose In this paper, a new structure for the permanent magnet hysteresis synchronous (PMHS) motor is introduced. Moreover, this paper aims to presents a new analytical method for modeling of a disc-type PMHS motor.Design/methodology/approach Because the hysteresis and permanent magnet motors have unique characteristics, a motor (the PMHS motor) with excellent performance features can be achieved by combining them. Choosing a disc-type slotless structure causes the major advantages of both motors to be preserved in the new motor. To analyze PMHS motor, mathematical equations are obtained by using Ampere’s circuital law, flux continuity law and Faraday’s law. Then the air-gap voltage and exciting current of the motor can be calculated. To implement this method, a new iterative algorithm is proposed. This algorithm consists of one-iteration loop for each input voltage to find the maximum flux density of the operational hysteresis loop of the motor.Findings Validity of the analytical approach is confirmed by experimental results. A reasonably close agreement between the two is shown and some outstanding performances of the PMHS motor are demonstrated.Originality/value A new structure for PMHS motor and also a new analytical method for performance prediction of this motor is presented. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to present an improved conformal mapping (ICM) method that simultaneously considers the influence of relative recoil permeability of PMs, the armature reaction, the stator slotting, and the magnetic saturation on determination of the PM operating point in its different parts.Design/methodology/approach The ICM method is a time-effective method that considers the magnetic saturation by suitable increments in air-gap length under each tooth and also the width of slot openings. In this paper, the analytical and numerical conformal mappings such as the Schwarz-Christoffel (SC) mapping are used for magnetic field analysis due to the permanent magnets and the armature reaction in one slotted air gap. The field solution in the slotted air gap is obtained through the modulation of field solution in one slotless air-gap using the complex air-gap permeance.Findings The ICM method can consider the magnetic saturation in different electric loadings, and also the variation of PM operating points in its different parts.Practical implications The ICM method is applied to one surface mounted permanent magnet (SMPM) motor and is verified by comparing with the corresponding results obtained through finite element method (FEM), and frozen permeability finite element method (FP-FEM).Originality/value This paper presents an ICM method with a new technique for saturation effect modeling, which can be used to separate and calculate the on-load components of air-gap field and torque. [ABSTRACT FROM AUTHOR]

Understanding Diabetes Prediabetes: The Gap between the Onset of Disease and Initiation of Treatment. Diabetes: A Dietitian's Perspective. Use of Modelling for Better Diabetes Care. No More Highs and Lows with Toujeo®: A New and Improved Insulin Injection. [ABSTRACT FROM AUTHOR]

We present a Python package for the efficient generation of special quasi-random structures (SQS) for atomic-scale calculations of disordered systems. Both, a Monte-Carlo approach or a systematic enumeration of structures can be used to carry out optimizations to ensure the best optimal configuration is found for given cell size and composition. We present a measure of randomness based on Warren-Cowley short-range order parameters allowing for fast analysis of atomic structures. Hence, optimal structures are found in a reasonable time for several dozens or even hundreds of atoms. Both SQS optimizations and analysis of structures can be carried out via a command-line interface or a Python API. Additional features, such as optimization towards partial ordering or independent sublattices allow the generation of atomistic models of modern complex materials. Moreover, hybrid parallelization, as well as distribution of vacancies, are supported. The output data format is compatible with ase, pymatgen and pyiron packages to be easily embeddable in complex simulation workflows. Program title: sqsgenerator CPC Library link to program files: https://doi.org/10.17632/m2sb3wzcvc.1 Developer's repository link: https://github.com/dgehringer/sqsgenerator Licensing provisions: MIT Programming language: Python, C++ Supplementary material: https://sqsgenerator.readthedocs.io Nature of problem: Many technological relevant materials, exhibit a crystalline disorder. Within atomistic modelling approaches such as Density Functional Theory (DFT) or Molecular Dynamics, disorder is modelled with a cell containing a (small) finite set of atoms. Such an atomic configuration is usually found by enumerating structures. However, since configurational space is growing exponentially efficient tools are needed to sample it properly. Solution method: Efficient quantification of disorder using a generalization of Warren-Cowley Short Range Order (WC-SRO) parameters [1,2]. By either a Monte-Carlo approach or systematic enumeration, optimal structures can be found. The software is distributed as a Python package offering a command line interface. Core parts are written in C++ and exhibit shared (OpenMP) and distributed (MPI) memory parallelism. For embedding into complex simulation workflows, the tool exposes a Python API to integrate into popular packages such as ase [3], pymatgen [4] or pyiron [5]. [1] J.M. Cowley, An approximate theory of order in alloys, Phys. Rev. 77 (5) (1950) 669–675. URL https://doi.org/10.1103/physrev.77.669. [2] J.M. Cowley, Short-range order and long-range order parameters, Phys. Rev. 138 (5A) (1965) A1384–A1389. URL https://doi.org/10.1103/physrev.138.a1384. [3] A.H. Larsen, J.J. Mortensen, J. Blomqvist, I.E. Castelli, R. Christensen, M. Dułak, J. Friis, M.N. Groves, B. Hammer, C. Hargus, E.D. Hermes, P.C. Jennings, P.B. Jensen, J. Kermode, J.R. Kitchin, E.L. Kolsbjerg, J. Kubal, K. Kaasbjerg, S. Lysgaard, J.B. Maronsson, T. Maxson, T. Olsen, L. Pastewka, A. Peterson, C. Rostgaard, J. Schiøtz, O. Schütt, M. Strange, K.S. Thygesen, T. Vegge, L. Vilhelmsen, M. Walter, Z. Zeng, K.W. Jacobsen, The atomic simulation environment—a python library for working with atoms, Journal of Physics: Condensed Matter 29 (27) (2017) 273002. URL http://stacks.iop.org/0953-8984/29/i=27/a=273002. [4] S.P. Ong, W.D. Richards, A. Jain, G. Hautier, M. Kocher, S. Cholia, D. Gunter, V.L. Chevrier, K.A. Persson, G. Ceder, Python materials genomics (pymatgen): A robust, open-source python library for materials analysis, Computational Materials Science 68 (2013) 314–319. URL https://doi.org/10.1016/j.commatsci.2012.10.028. [5] J. Janssen, S. Surendralal, Y. Lysogorskiy, M. Todorova, T. Hickel, R. Drautz, J. Neugebauer, pyiron: An integrated development environment for computational materials science, Computational Materials Science 163 (2019) 24–36. URL https://doi.org/10.1016/j.commatsci.2018.07.043. • A Python package for efficient generation of special quasi-random structures (SQS) has been developed. • Optimal SQS structures are found in a reasonable time even for dozens of atoms. • Monte-Carlo approach or a systematic enumeration of structures can be used to carry out optimizations. • The output is compatible with ase, pymatgen and pyiron for embedding in complex simulation workflows. • YAML format is used as the default for both the input and output files. [ABSTRACT FROM AUTHOR]

Modeling complex dynamical systems from heterogeneous pieces of knowledge varying in precision and reliability is a challenging task. We propose the combination of dynamical Bayesian networks and of imprecise probabilities to solve it. In order to limit the computational burden and to make interpretation easier, we also propose to encode pieces of (numerical) knowledge as probability intervals, which are then used in an imprecise Dirichlet model to update our knowledge. The idea is to obtain a model flexible enough so that it can easily cope with different uncertainties (i.e., stochastic and epistemic), integrate new pieces of knowledge as they arrive and be of limited computational complexity. [ABSTRACT FROM AUTHOR]

Purpose The mathematical complexity of the BJ(x) Brillouin function makes it unsuitable for most calculations and its application difficult for computer programming in magnetism. Here, its approximation with the tanh function is proposed to ease the mathematical operations for most cases. The approximation works with good accuracy, acceptable in practical calculations. This approximation has already formed the foundation of the “hyperbolic model” in magnetism for the study of hysteretic phenomena. The reversal of the Brillouin function is an important but difficult mathematical problem for practical purposes. Here, a proposal has been put forward for an easy approximation using an analytical expression. This provides a good workable solution for the BJ(x)−1 function dependent on J, the angular momentum quantum number of the material used. The proposed approximation is applicable within the working range of practical applications. The paper aims to discuss these issues.Design/methodology/approach The multi-variant Brillouin function is closely approximated by the tanh function to ease calculations. Its mathematically unsolved reversed function is approximated by a simple analytical expression with a good working accuracy.Findings The Brillouin function and its reversal can be approximated for practical users mostly for professionals working in Magnetism.Research limitations/implications Most if not all practical problems in Magnetism can be solved within the limitations of the two approximations.Practical implications Both proposed functions can ease the mathematical problems faced by researchers and other users in Magnetism.Social implications Ease the frustration of most users working in the field of Magnetism.Originality/value The application of the tanh function for replacing the Brillouin function led to the creation of the hyperbolic model of hysteresis. To the author's knowledge, the reverse function was mathematically only solved in 2015 with a vastly complicated mathematics, and is hardly suitable for practical calculations in Magnetism. The proposed simple expression can be very useful for theorists and experimental scientists. [ABSTRACT FROM AUTHOR]