General Simulation Model Research Articles

Discrete-event simulation to analyse the impacts of a reduced minimum order quantity in the food industry: proposing a shared-savings contract

ABSTRACT Retail partners of the food processing industry benefit from lower minimum order quantities, as they are more responsive to changing market conditions and reduce inventory costs. However, production systems in the food processing industry focus on economies of scale by producing large volumes. A shared-savings contract helps to find a trade-off between the two parties, where the retailer shares a part of the cost savings with the manufacturer to cope with higher production costs. We propose a generic data-driven discrete-event simulation model to guide decision-making in the development of a shared-savings contract. Thereby, we examined breakdown and rework behaviours after setups with a Big Data analysis and a correlation analysis. We aim to evaluate the cost development at a cheese processing company, resulting from a reduced minimum order quantity. Our findings revealed that production costs significantly increase with higher breakdowns, setups, and rework. A 20% increase in orders, resulting from a reduced minimum order quantity, requires an additional production capacity of 3%. To conclude, transparent information sharing is key to developing a shared-savings contract in the food supply chain.

Dynamic simulation of a simply supported beam subjected by multiple constant moving forces

Abstract Dynamic simulation models, which are conducted with Simulink, are introduced to study behaviors of a simply supported beam under constant moving forces based on the vibration mechanics model established by Bernoulli-Euler beam theory. By utilizing the orthogonality of vibration, a set of decoupled forced vibration equations can be obtained, which can be constructed as a subsystem of the Simulink model. The generalized loads in each decoupled vibration equation are also separately formed into submodules to facilitate the extension of the action of a single moving load to multiple moving loads. Every partial and general simulation model in Matlab/Simulink are made and the simulation results indicate that dynamic responses are related to the distance between moving loads and beam span.

A Synthesis on Impact Assessment Models from the Perspective of Evolution of the EU Common Agricultural Policy

Purpose: This paper aims to provide a comprehensive analysis of the current quantitative impact assessment methodologies, examining their strengths and weaknesses in terms of data requirements, as well as their consideration of social, economic, and environmental factors. Furthermore, it aims to elucidate the necessity for new-generation agricultural impact assessment models to incorporate advancements in information technology, communication tools, and big data analytics. Design/Methodology/Approach: In this review, the term "agricultural modelling platforms" is used to denote different equilibrium models and these models are divided into two categories according on their methodological approaches. The first category adopts a "systems approach," which includes general and partial equilibrium type models, as well as sector models. The "agent-based approach" is used by the second category. This review, thus, is primarily concerned with contrasting farm-representative models with farm-based models. Findings: The study emphasizes the importance of methodology and criteria in modelling exercises, considering factors like analysis level, environmental impact, and relationship between agriculture and the environment. It suggests that selecting the right modelling scale and tool requires asking the right research questions in advance. Originality/Value: In this study, general and partial equilibrium models, which allow impact analysis of policies implemented in the agricultural sector, which is increasingly faced with ecological and social problems, and Agent Based Models (ABM), which allow the problems in question to be included in the models, are compared and provided guidance to policy makers. It is aimed to reveal their advantages/disadvantages against each other. The originality of this study is that this comparison is made by taking into account the evolution of the European Common Agricultural Policy (CAP) since its establishment.

Assessing Reliability, Resilience and Vulnerability of Water Supply from SuDS

In recent decades, the impacts of urbanization on the hydrological cycle have led to an increase in the frequency and magnitude of urban flooding events, and this is also amplified by the effects of climate change. Sustainable Drainage Systems (SuDS) provide a revolutionary change in this field, improving the sustainability and resilience of cities. This research explores the integration of different SuDS with the aim of significantly reducing both the flow volume and celerity of floods in a residual urban catchment area of the metropolitan city of Querétaro (Mèxico), where extreme rainfall frequently occurs. This catchment is a representative suburb of urban pressure and environmental degradation problems. Currently, managing storm water under climate uncertainty through a multi-disciplinary approach is a major concern in this urban area. A 1D–2D coupling model of shallow water equations, the finite volume method, an unstructured meshing method, and a hybrid parallel computing application defined the optimal configuration of SuDS at catchment scale to reduce the flood vulnerability in Querétaro. Specifically, in this paper, we explore the management issues of the proposed SuDS configuration that acts as a water resource system with multiple purposes. A generic simulation model called MODSIM was applied to simulate the designed urban drainage system under a balanced IPCC future climate scenario in terms of reliability, resilience and vulnerability against water scarcity. The proposed hierarchical Reliability–Resilience–Vulnerability approach appears to be effective in evaluating the system performance, showing that the complete satisfaction of non-essential water uses in Querétaro can be assured at a 65% rate of reliability for a large range of reservoir storage conditions.

Toxicokinetic relationship between the adducts in globin and their cleavage products in the urine: Implications for human biomonitoring

Globin adducts of various chemicals, persisting in organism over the whole lifetime of erythrocytes, have been used as biomarkers of cumulative exposures to parent compounds. After removal of aged erythrocytes from the bloodstream, cleavage products of these adducts are excreted with urine as alternative, non-invasively accessible biomarkers. In our biomonitoring studies on workers exposed to ethylene oxide, its adduct with globin, N-(2-hydroxyethyl)valine, and the related urinary cleavage product N-(2-hydroxyethyl)-L-valyl-L-leucine have been determined. To describe a toxicokinetic relationship between the above types of biomarkers, a general compartmental model for simulation of formation and removal of globin adducts has been constructed in the form of code in R statistical computing environment. The essential input variables include lifetime of erythrocytes, extent of adduct formation following a single defined exposure, and parameters of exposure scenario, while other possible variables are optional. It was shown that both biomarkers reflect the past exposures differently as the adduct level in globin is a mean value of adduct levels across all compartments (subpopulations of erythrocytes of the same age) while excretion of cleavage products reflects the adduct level in the oldest compartment. Application of the model to various scenarios of continuous exposure demonstrated its usefulness for human biomonitoring data interpretation.

Optimal Allocation of Water Resources in Ordos City Based on the General Water Allocation and Simulation Model

This study aims to achieve coordination between regional economic development and ecological environmental protection and to mitigate issues such as competition for water use among industries and significant disparities between water supply and demand. A multi-water-source, multi-user, and multi-objective optimal water resource allocation model was developed for Ordos City using general water allocation and simulation (GWAS). This model was applied to optimize water resource allocation on a monthly scale for various users across different administrative units (banners) in both short- and long-term planning periods. The results indicate that Ordos City’s allocated water volume for 2025 and 2030 is projected to be 1833.36 × 106 m3 and 1963.44 × 106 m3, respectively, with an overall water shortage rate of 5.46% and 5.67%, respectively. Water shortages are predicted in Dongsheng District, Dalad Banner, Etuoke Banner, Hangjin Banner, and Wushen Banner, primarily during the agricultural water usage period from March to November. The regional water supply structure was notably optimized, with a gradual decrease in the proportion of groundwater in the total water supply and a corresponding increase in the supply of surface water and unconventional water. These changes effectively improve local groundwater overexploitation and enhance the water supply efficiency. The research findings could offer valuable theoretical and technical support for the development and utilization of water resources, as well as for adjustments in the population–economic–industrial structure of Ordos City. Additionally, this study could provide scientific references for optimizing water resource allocation in other water-deficient cities in arid and semi-arid areas of the Yellow River Basin.

Nonlinear Electron Trapping Through Cyclotron Resonance in the Formation of Chorus Subpackets

AbstractChorus subpackets are the wave packets with modulated amplitudes in chorus waves, commonly observed in the magnetospheres of Earth and other planets. Nonlinear wave‐particle interactions have been suggested to play an important role in subpacket formation, yet the corresponding electron dynamics remain not fully understood. In this study, we have investigated the electron trapping through cyclotron resonance with subpackets, using a self‐consistent general curvilinear plasma simulation code simulation model in dipole fields. The electron trapping period has been quantified separately through electron dynamic analysis and theoretical derivation. Both methods indicate that the electron trapping period is shorter than the subpacket period/duration. We have further established the relation between electron trapping period and subpacket period through statistical analysis using simulation and observational data. Our study demonstrates that the nonlinear electron trapping through cyclotron resonance is the dominant mechanism responsible for subpacket formation.

Evolution Kinetics of Stabilizing Pickering Emulsion by Brush-Modified Janus Particles: DPD Simulation and Experimental Insights.

In the present study, we report the evolution of stabilizing Pickering emulsions using brush-modified Janus particles (JPs), utilizing the dissipative particle dynamics (DPD) simulation technique. Our results are subsequently corroborated with experimental findings. Each JP has one-half of the hydrophobic surface, with the other half embedded with hydrophilic polymer brushes grown via atom transfer radical polymerization (ATRP). Our generic simulation model analyzes the chemical kinetics of polymer brush growth on one-half of the initiator-embedded microparticle (MP) surface, resulting in the formation of JP. This involves evaluating monomer conversion and reaction rates. Our results exhibit a substantial influence of the number of JPs, grafted brush density, and brush length on oil-in-water emulsion stability. We studied the evolution kinetics and stability of emulsion formation by analyzing the growth of average domain size and corresponding scaling functions up to a late time limit. This study aims to clarify the connection between the size, quantity, and functionality of JPs and the stability of Pickering emulsions.

Research on longitudinal control technology in the transition section of tilt-rotor aircraft based on linear active disturbance rejection control

To solve the problem of strong coupling and control redundancy in the transition section of the tilt-rotor, this paper presents a longitudinal control method based on linear active disturbance rejection control (LADRC), verified by simulation. Firstly, the nonlinear dynamics model of tilt-rotor aircraft based on the mechanism method is established, and the model’s accuracy is verified by comparing the trim result with the generic tilt-rotor aircraft simulation (GTRS) model verified by flight test in XV-15. Then, the control and redundant rudder surface assignment strategies for tilt-rotor aircraft are proposed. Then, the vertical and vertical control law of tilt-rotor aircraft is designed, the linear expansion state observer (LESO) model is analyzed and derived, and the linear active disturbance rejection controller suitable for attitude loop control of tilt-rotor is designed. The altitude and velocity loops are controlled. Finally, the proposed linear active disturbance rejection control (LADRC) controller is verified by simulation, and the whole process of tilting transition is simulated. The results show that the proposed control strategy and the controller designed in this paper have strong anti-disturbance ability, fast response speed, and high control precision and can be used in the transition section of tilt-rotor aircraft. The vertical direction shall be well controlled.

A fast general thermal simulation model based on Multi-Branch Physics-Informed deep operator neural network

Thermal simulation plays a crucial role in various fields, often involving complex partial differential equation (PDE) simulations for thermal optimization. To tackle this challenge, we have harnessed neural networks for thermal prediction, specifically employing deep neural networks as a universal solver for PDEs. This innovative approach has garnered significant attention in the scientific community. While Physics-Informed Neural Networks (PINNs) have been introduced for thermal prediction using deep neural networks, existing methods primarily focus on offering thermal simulations for predefined relevant parameters, such as heat sources, loads, boundaries, and initial conditions. However, any adjustments to these parameters typically require retraining or transfer learning, resulting in considerable additional work. To overcome this limitation, we integrated PINN methods with the DeepONet model, creating a novel model called PI-DeepONet for thermal simulation. This model takes both relevant parameters and coordinate points as simultaneous input functions, presenting a fresh computational perspective for thermal simulation. Based on the PaddlePaddle deep learning framework, our research demonstrates that after sufficient training, this model can reliably and rapidly predict parameter solutions. Importantly, it significantly surpasses traditional numerical solvers in terms of speed by several orders of magnitude, without requiring additional training. This groundbreaking research framework holds vast application potential and promises substantial advancements in the field of thermal simulation.

Modeling of multi-temperature Type I and II benzene/ammonia adsorption isotherms: Dual LF model and linearized DR model

Adsorption isotherm is basic data for evaluating the porous adsorbent adsorption capacity and explaining gas–solid adsorption behavior. Adsorption equilibrium modeling is a simple method to describe isotherm data in application. In this paper, taking C6H6 and NH3 as an example, multi-temperature Type I or Type II adsorption isotherms on AC, ASZMT, and 13X were investigated and fitted. Results show that C6H6 and NH3 adsorption behaviors on 13X both existed in chemisorption. At certain adsorbed capacity, the isosteric heats are higher than 50 kJ·mol−1. Type I and Type II C6H6 or NH3 adsorption isotherms could be successfully described using the extended Dual LF model·NH3 temperature-independent characteristic curves on AC and ASZMT were obtained using the Linearized DR model and successfully used to predict NH3 adsorption data at any pressure within the whole room temperature. Further, the Dual LF model was extended to describe other adsorption isotherms including IUPAC Type III, IV, and V. The R2 between the model and data were higher than 0.98, proving that it has universal applicability than other classical models such as Langmuir, Freundlich, Toth, and so on. It has the potential to be used as a general equilibrium model for adsorption process simulation in the future.

Tiltrotor Simulations with Coupled Flight Dynamics, State-Space Aeromechanics, and Aeroacoustics

This article describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustics. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model. This way, the flight dynamics are augmented by the vortex wake dynamics so that the coupled flight and wake dynamics are self-contained and inherently linearizable. The model is implemented for a Bell XV-15 tiltrotor and validated against U. S. Army/NASA XV-15 flight-test data and other data in the literature. Flight control design is performed to provide desired stability, performance, and handling-quality properties and to allow for a fully autonomous transition between hover in helicopter mode and highspeed flight in aircraft mode. The simulation model has clear applications in the development and testing of advanced flight control laws, aeromechanics analysis, and the prediction of aerodynamically generated noise in generalized maneuvering flight.

Thermal performance of indoor solar shading devices using a thermal nodal model and a lighting simulation model

Various facade designs, such as light shelves, have been proposed to achieve zero emission buildings. However, general thermal load simulation models are unable to properly evaluate the thermal effects of spaces near windows, such as light shelves and counters, which are installed on the interior side of windows for increased daylight utilization. In this study, we propose a method to evaluate the thermal performance of indoor light shelves. The model proposed herein consists of three components: A thermal nodal model of the window area, a lighting simulation model, and a thermal simulation model. The thermal nodal model places a node at each device (glass, ceiling, light shelf, and floor) in the light shelf space. The heat balance equation for each node is then solved. In doing so, the total transmittance of the entire indoor-installed device space, which considers inter-reflections and the solar radiation absorptance of each device, is calculated using the Radiance software. Additionally, the solar heat gain obtained using the thermal nodal model is substituted internally into NewHASP, and the thermal load calculation is performed. Finally, a simulation is performed using an office model, and the indoor-installed light shelf exhibited a 14 % reduction in annual thermal load.

Sustainable Energy Planning and Modelling for Global South: A Case Study of the Federal Republic of Nigeria.

This paper reviews the literature regarding the inherent limitations of Modeling practices for sustainable energy planning in the Global South (GS).GS is undergoing economic changes in its energy-setting socio-economic policies such as liberalisation, financial sourcing, and climate change implications of energy projects. Long-term energy planning lays the foundations for effective policies, investment strategies, and targets at the national or regional level. An astute and up-to-date master plan for energy development fosters predictable investment conditions. This makes it an essential prerequisite for scaling up renewable energy technologies. Active energy planning, built on quantitative setting Modeling and stakeholder consultations, allows policymakers to understand and explore the complexities and uncertainties of future energy system evolution. Modeling and simulation (M&S) is a well-known scientific technique that could analyse a system or predict its behaviour before physical construction. Despite being an established methodical tool in engineering, only a few review articles discussing emerging topics in M&S are available in the open literature, especially for renewable and sustainable energy systems. The International Renewable Energy Agency (IRENA) offers energy planning Support, as a guide, with a view to enhancing institutional capacity at the country level and strengthening each country’s ownership of the planning process. The capacity to interpret key energy data into strong energy planning enables nations to develop all-inclusive national energy master plans and to frequently update these as the basis for comprehensive policies and investments. This paper examines the current Modeling and simulation of the energy sector with insights into the approaches, challenges, and prospects of certain selected and suitable energy systems. Additionally, it reveals the limitations of traditional planning tools such as optimisation, econometric, and general simulation models. The paper posits that traditional approaches are inadequate for SED in the GS due to its inherent weakness in guiding future policy decisions. In this work, the 7th SDG: Affordable and Clean Energy, is brought into focus. The paper addresses the Planning approaches, tools, framework, and techniques as revealed in the literature on energy Modeling and policy formulation. The aim is to enhance the country's capacity to analyse energy data and develop scenarios using Modeling tools for long-term energy planning. The additional tools to support energy planning may be selected according to each country’s needs and existing Modeling expertise. Finally, areas that need further research and development in sustainable energy Modeling are highlighted. Keywords: Sustainability, Energy Planning, Modelling, Global South. Proceedings Citation Format Abraham Rasheed Adeyemi (2023): Sustainable Energy Planning and Modelling for Global South: A Case Study of the Federal Republic of Nigeria.. Proceedings of the 37th iSTEAMS Multidisciplinary Cross-Border Conference. 30th October – 1st November, 2023. Academic City University College, Accra, Ghana. Pp 93-106. dx.doi.org/10.22624/AIMS/ACCRACROSSBORDER2023V2P8

Comparing intervention measures in a model of a disease outbreak on a university campus.

A number of theoretical models have been developed in recent years modelling epidemic spread in educational settings such as universities, often as part of efforts to inform re-opening strategies during the COVID-19 pandemic. However, these studies have had differing conclusions as to the most effective non-pharmaceutical interventions. They also largely assumed permanent acquired immunity, meaning we have less understanding of how disease dynamics will play out when immunity wanes. Here, we complement these studies by developing and analysing a general stochastic simulation model of disease spread on a university campus where we allow immunity to wane, exploring the effectiveness of different interventions. We find that the two most effective interventions to limit the severity of a disease outbreak are reducing extra-household mixing and surveillance testing backed-up by a moderate isolation period. We find that contact tracing only has a limited effect, while reducing class sizes only has much effect if extra-household mixing is already low. We identify a range of measures that can not only limit an outbreak but prevent it entirely, and also comment on the variation in measures of severity that emerge from our stochastic simulations. We hope that our model may help in designing effective strategies for universities in future disease outbreaks.

First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization

Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (〈∣v∣〉 < 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (∣v int∣ < 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*.

Research on generic electromechanical transient simulation model of distributed solar photovoltaic power generation

Research on generic electromechanical transient simulation model of distributed solar photovoltaic power generation

Dominant factors in the simulation-based development of warehousing services

ABSTRACT Robust solutions are needed in the context of warehouse planning in contract logistics. To achieve this goal, knowledge about dominant factors is a prerequisite and thus presents the aim of this research. The factors to be evaluated are identified through a literature analysis, which leads to more than 40 factors from over 30 sources. To explore a broad range of factors, including their interaction, a design of experiments approach is used in a generic simulation model applied in a multiple-case study. The results indicate the overall dominance of demand-related factors and also the high importance of the equipment specifications across cases. Consequently, managerial insights include a shift of planning resources towards these most dominant factors. Based on the research results, the focus should be on a thorough analysis of the demand structure and the characteristics of the technical equipment. Also, when employing simulation models for the planning of order picking systems, it is strongly advised to use a parameter variation which draws a multifaceted picture of the situation in order to enable a justified decision. Implications for warehouse research are the consideration of variable input, especially regarding demand characteristics, to create relevant order picking scenarios when testing the optimisation potential of new developments.

CITIES: Clinical trials with intercurrent events simulator.

Although clinical trials are often designed with randomization and well-controlled protocols, complications will inevitably arise in the presence of intercurrent events (ICEs) such as treatment discontinuation. These can lead to missing outcome data and possibly confounding causal inference when the missingness is a function of a latent stratification of patients defined by intermediate outcomes. The pharmaceutical industry has been focused on developing new methods that can yield pertinent causal inferences in trials with ICEs. However, it is difficult to compare the properties of different methods developed in this endeavor as real-life clinical trial data cannot be easily shared to provide benchmark data sets. Furthermore, different methods consider distinct assumptions for the underlying data-generating mechanisms, and simulation studies often are customized to specific situations or methods. We develop a novel, general simulation model and corresponding Shiny application in R for clinical trials with ICEs, aptly named the Clinical Trials with Intercurrent Events Simulator (CITIES). It is formulated under the Rubin Causal Model where the considered treatment effects account for ICEs in clinical trials with repeated measures. CITIES facilitates the effective generation of data that resemble real-life clinical trials with respect to their reported summary statistics, without requiring the use of the original trial data. We illustrate the utility of CITIES via two case studies involving real-life clinical trials that demonstrate how CITIES provides a comprehensive tool for practitioners in the pharmaceutical industry to compare methods for the analysis of clinical trials with ICEs on identical, benchmark settings that resemble real-lifetrials.

A Unified Model of Coherent Direction-of-Arrival Simulation for Radar Target Simulators

In order to simulate highly realistic scenarios for modern radar sensors, like traffic scenarios, radar target simulators require the capability to generate targets in all four radar dimensions, which are range, radial velocity, azimuth and elevation angle. To generate targets with angular information, coherent direction-of-arrival (DoA) simulation allows a highly accurate and flexible angular simulation, at a minimum of required hardware. In this article a unifying general model for coherent DoA simulation with channel knowledge for radar target simulators is derived. It comprises previous models. We present methods which allow the simulation of arbitrary and adjustable DoAs, without any constraints on the radar array geometry or the implemented beamformer. The proposed models and methods are analytically derived, analyzed by simulations and finally verified by measurements. Lastly, a measurement of a 2D-DoA simulation for a radar with twelve channels is conducted, in order to show the general applicability of the concept.