Simple Simulation Model Research Articles

Free Will in the World as a Computer Simulation

The article discusses the original many-worlds version based on the model of the world as a computer simulation, namely the space of a video game. Based on the interpretation of Benjamin Libet's experiment an assumption is made about how a person can function in a virtual game reality being and perceived as basic. This case shows that the question of the freedom of a person`s actions acquires a new meaning. In particular, in this situation, the acting person is proved to be actually deprived of the opportunity to act since decisions are made for him by someone else, for whom, in turn, decisions could be also someone else`s. The implementation of the described in the article scenario is theoretically possible — on obligatory condition of the successful creation of artificial intelligence and the availability of technical capacities which are necessary for the functioning of complex virtual systems. Obviously, at the moment neither one nor the other has been developed. But this is a highly topical issue and in modern scientific This work uses modeling and intellectual experiment methods: a simplified simulation model of a popular open-world video game is taken to demonstrate the main idea. Its example shows how the observable world can be realized — one of the possible versions of the multiverse.

Nonlinear and chaotic dynamics of a vibratory conveying system

In this work, a simulation model of a vibratory conveying system is presented. The simulation model is based on a continuous contact formulation in vertical direction which is extended by a friction force in horizontal direction to simulate a conveying process. In contrast with complex 3D simulation tools, it enables the understanding of previously unexplained phenomena such as multiple feeding velocities at the same excitation amplitude, which are observed in practical measurements. The parameters that have an influence on this effect are investigated, and a method for predicting and adjusting the occurrence of multiple solutions is developed. It is shown that the calibration of the system is very difficult in practice, as it depends significantly on the initial conditions which are difficult to reproduce and predict. It is also shown that the system can exhibit chaotic behavior in some configurations. These chaotic states are shown with the simulation model by means of parameter studies, and the point at which the system becomes chaotic is predicted with the method of Lyapunov exponents and fractal dimensions. Knowledge of the chaotic states can be used to calibrate the conveyor, as they depend only on the excitation and not on the initial conditions. The interdependencies of the initial conditions are also discussed in more detail. Therefore, this work provides a deeper understanding of complex conveying processes using a simple simulation model.

Efficient modeling of DFIG- and FSC-based wind turbines for frequency stability analysis

The contribution of wind turbines (WTs) to enhance the frequency stability of power systems is traditionally analyzed using commonly applied root mean square (RMS) models. RMS WT models require smaller simulation time steps compared to conventional active devices (i.e., synchronous generators and dynamic loads) due to the comparatively smaller time constants of the converter controllers. Such small time steps become relevant in simulations of large-scale power systems with a high level of WT penetration and lead to high computational time and effort. This paper presents simplified simulation models of a doubly-fed induction generator-based WT and a full-scale converter-based WT, which enable higher simulation time steps due to the negligence of very small time constants with no relevant effects in the time frame of interest of frequency stability analysis. The models are derived from detailed RMS WT models based on fundamental machine and converter equations. In order to verify the validity of the underlying simplifications, the simplified models are compared to the detailed RMS models with a focus on their general behavior in case of step responses and their frequency responses in the event of a frequency drop in a 220 kV test system. For this purpose, both the detailed RMS WT models as well as the simplified WT models are extended with a droop-based fast frequency response controller and implemented in a MATLAB-based RMS simulation tool. The results of the case studies show feasible and comparable general behavior of the WT models as well as plausible frequency responses.

Self-consistent solution of magnetic and friction energy losses of a magnetic nanoparticle

We present a simple simulation model for analyzing magnetic and frictional losses of magnetic nanoparticles in viscous fluids subject to alternating magnetic fields. Assuming a particle size below the single-domain limit, we use a macrospin approach and solve the Landau-Lifshitz-Gilbert equation coupled to the mechanical torque equation. Despite its simplicity the presented model exhibits surprisingly rich physics and enables a detailed analysis of the different loss processes depending on field parameters and initial arrangement of the particle and the field. Depending on those parameters regions of different steady states emerge: a region with dominating magnetic relaxation and high magnetic losses and another region region with high frictional losses at low fields or low frequencies. The energy increases continuously even across regime boundaries up to frequencies above the viscous relaxation limit. At those higher frequencies the steady state can also depend on the initial orientation of the particle in the external field. The general behavior and special cases and their specific absorption rates are compared and discussed.

Microphase separation of living cells

Self-organization of cells is central to a variety of biological systems and physical concepts of condensed matter have proven instrumental in deciphering some of their properties. Here we show that microphase separation, long studied in polymeric materials and other inert systems, has a natural counterpart in living cells. When placed below a millimetric film of liquid nutritive medium, a quasi two-dimensional, high-density population of Dictyostelium discoideum cells spontaneously assembles into compact domains. Their typical size of 100 μm is governed by a balance between competing interactions: an adhesion acting as a short-range attraction and promoting aggregation, and an effective long-range repulsion stemming from aerotaxis in near anoxic condition. Experimental data, a simple model and cell-based simulations all support this scenario. Our findings establish a generic mechanism for self-organization of living cells and highlight oxygen regulation as an emergent organizing principle for biological matter.

Measurement of Tire-Pavement Contact Tri-Axial Stress Distribution Based on Sensor Array

A tire’s three-dimensional stress for pavement is an important cause of asphalt pavement disease. In order to study the contact stress distribution between the tire and the pavement under real conditions, a sensor that can measure the tri-axial stress synchronously is designed, and a complete measurement system is established. The variation trend and stress value of tri-axial stress under steady rolling of the tire were obtained, and the stress distribution characteristics were analyzed. The results show that the stress in the three directions near the tire shoulder is greater than that in the crown area, and the stress peak moves gradually from front to back with the rolling of the tire. Compared with the simplified simulation model, these results provides valuable suggestions for exploring the real tire-pavement interaction.

Simulation based testing and performance investigation of induction motor drives using matlab simulink

Induction motors (IMs) are the most widely employed electrical motors due to their robust construction and adaptability. Due to their versatility and wide range of applications, it is crucial to examine the performance of these motors using a simple but thorough simulation model. In this study, we present the simulation models to conduct the DC test, the no-load test, and the locked rotor test on a three-phase induction motor using MATLAB/Simulink. These three tests are fundamental to determining the characteristics of a three-phase induction motor equivalent circuit. Furthermore, the authors extend the model to determine the starting current, starting torque, and breakdown torque of the motors under inquiry. The research further employs the right code in the MATLAB environment to ascertain the motors' torque-speed and current-speed properties. The results of the simulations are found to closely match the values achieved in real trials. Hence, this model can be employed to enhance teaching and research in the field of electrical machinery.Article HighlightsThis paper explains a computerized procedure employing MATLAB software to carry out vital tests on induction motors. The research shows that using the methods described in this paper, induction motors can be safely tested for their operating characteristics.The benefit of the computerized methodology described in this paper is that it provides a modelling tool and methodology to expand research on induction motors with high accuracy and reliability.The numerical method developed in this article is a suitable tool in teaching and education.Beyond the three common tests (dc test, no-load test and locked rotor test) to determine the equivalent circuit of induction motors, this paper further extends the research to use the simulation models to determine the starting current, starting torque and the breakdown torque of an induction motor as well as its torque-speed and current-speed characteristics.

Numerical optimization of highly loaded microtextured contacts: understanding and mastering complexity

PurposeMicrotextured surfaces can reduce friction in tribological systems under certain contact conditions. Because it is very time-consuming to determine suitable texture patterns experimentally, numerical approaches to the design of microtextures are increasingly gaining acceptance. The purpose of this paper is to investigate to what extent the selected modeling approach affects optimized texturing.Design/methodology/approachUsing the cam/tappet contact as an application-oriented example, a simplified 2D and a full 3D model are developed for determining the best possible texturing via a design study. The study explores elongated Gaussian-shaped texture elements for this purpose. The optima of the simplified 2D simulation model and the full 3D model are compared with each other to draw conclusions about the influence of the modeling strategy. The target value here is the solid body friction in contact.FindingsFor the elongated texture elements used, both the simplified 2D model and the full model result in very similar optimal texture patterns. In the selected application, the simplified simulation model can significantly reduce the computational effort without affecting the optimization result.Originality/valueDepending on the selected use case, the simulation effort required for microtexture optimization can be significantly reduced by comparing different models first. Therefore, an exact physical replica of the real contact is not necessarily the primary goal when it comes to texture selection based on numerical simulations.

Characterisation of the conveying effect of turned radial shaft seal counter-surfaces using a simplified hydrodynamic simulation model

AbstractA typical sealing system for rotating shafts consists of the radial shaft sealing ring (RSS), the lubricant and the shaft counter-surface (SCS) of the rotating shaft. The properties of the machined surface of the SCS have an impact on the sealing system. The structural pattern of the SCS influences the lubricant flow along the axial direction. In this paper, a simplified micro scale hydrodynamic simulation model is presented in order to study and determine the axial flow of the lubricant induced by the SCS of the sealing system, isolated from the effects induced by the seal, to allow for a rating of the shaft surface. The influence of the seal was neglected to allow for a simplified simulation. Simulated shaft surfaces corresponding to different machining parameters of machined SCS are used as input. These variants of SCS were created using a kinematic model which simulates an ideal surface machining process of the shaft. A micro scale hydrodynamic simulation model is used to investigate the influence of machining parameters on the lubricant flow along the axial direction across the tribo-contact. From this investigation, the connection between parameters applied for machining of the SCS and conveying effects can be estimated. The simulation model is also validated with experimental results of hard turned shafts of different machining parameters. Differences between manufactured real surfaces and kinematically simulated surfaces are the cause of deviations between the results.

Emergent magnetic-nonmagnetic transition in strain-tuned zigzag-edged PtSe2 nanoribbon

Magnetic responses in nonmagnetic transition metal dichalcogenides (TMDs) via reduced dimension and defect engineering continue to bring forth emergent properties and has revolutionized important technologies such as data storage and magnetic sensing. Using the first-principles calculation, we investigate the zigzag-edged ${\mathrm{PtSe}}_{2}$ (zz-${\mathrm{PtSe}}_{2}$) nanoribbon with a sizable magnetization solely at the zigzag edges and a remarkable magnetic-nonmagnetic switching induced by a small compressive uniaxial strain of about \ensuremath{-}2%. We further interpret the sudden disappearance of the magnetization by a simple but clear model simulation considering the localized quasi-one-dimensional magnetic channels mediated by metallic backgrounds along the edges. Such newly proposed strain-controlled magnetic transition through band structure engineering highlights zz-${\mathrm{PtSe}}_{2}$ as a unique candidate for controllable TMD-based one-dimensional magnets with promising advances in fundamental physics and technological opportunities in spintronics, computing, and sensors.

Compliant mechanical response of the ultrafast folding protein EnHD under force

Ultrafast folding proteins have become an important paradigm in the study of protein folding dynamics. Due to their low energetic barriers and fast kinetics, they are amenable for study by both experiment and simulation. However, single molecule force spectroscopy experiments on these systems are challenging as these proteins do not provide the mechanical fingerprints characteristic of more mechanically stable proteins, which makes it difficult to extract information about the folding dynamics of the molecule. Here, we investigate the unfolding of the ultrafast protein Engrailed Homeodomain (EnHD) by single-molecule atomic force microscopy experiments. Constant speed experiments on EnHD result in featureless transitions typical of compliant proteins. However, in the force-ramp mode we recover sigmoidal curves that we interpret as a very compliant protein that folds and unfolds many times over a marginal barrier. This is supported by a simple theoretical model and coarse-grained molecular simulations. Our results show the ability of force to modulate the unfolding dynamics of ultrafast folding proteins.

A novel simulation model for tube thoracostomy.

Tube thoracostomy is a life-saving procedure that must be performed competently and expeditiously by emergency care providers. The primary objective of this project was to develop a simple, easily-reproducible, and realistic simulation model for tube thoracostomy placement by learners of emergency medicine. This chest tube simulator utilizes two slabs of pork ribs with associated intercostal muscle and fascial planes to aid learners in identifying anatomic landmarks, palpating intercostal spaces, and performing blunt dissection in a manner that approximates human anatomy. Holes are cut on both sides of a 1.8-bushel capacity rectangular plastic clothing hamper, and rib slabs are secured to the hamper with zip ties or metal wire. A bed pillow with plastic cover is then placed inside of the plastic hamper to simulate lung tissue. The rib-hamper complex is then wrapped with cellophane or elastic compression bandages to further anchor the rib slabs and simulate skin and subcutaneous tissues. The initial cost of our thoracostomy model is approximately $50, much less than the $1,000-$3,000 cost for a commercial model. Although the hamper and pillow can be reused an indefinite number of times, the other components of our model must be replaced occasionally. Assuming a lifespan of 1,000 uses, our model costs approximately $1.78 per attempt, compared to $4.00 per attempt with the cheapest commercial mannequin system. In fact, assuming a longer useful lifespan for the mannequin does not substantially improve this comparison (e.g. $3.10 versus $1.77 per attempt for a 10,000 attempt lifespan for the commercial mannequin), largely due to the higher cost of commercial replacement skin pads when compared to the components consumed in our model with each attempt. We describe a porcine thoracostomy model that simulates the look and feel of human ribs for purposes of tube thoracostomy training, although it could also be used for thoracentesis and thoracotomy simulation. This model is relatively cheap (costing around $50) and easy to produce within a few minutes utilizing commonly-available materials. Further study is needed to determine whether an inexpensive model like ours provides the same educational value as more expensive commercial mannequin models.

Bridging the Gap Between Simple Metrics and Model Simulations of Climate Change Impacts on Land Hydrology

AbstractFor many years now, studies on climate change impacts on continental hydrology have suffered from conflicting results between different approaches. On the one hand, studies relying on widely used, simple metrics of land water availability, such as the Aridity Index and Palmer Drought Severity Index, depict predominantly drier future land surface conditions, when driven by climate change projections from global models. On the other hand, the same climate models also generate their own land surface projections, which exhibit balanced changes in land hydrology, with spatially heterogenous changes in soil moisture or runoff. Writing in Earth's Future, Scheff et al. (2022, https://doi.org/10.1029/2022ef002814) provide a comprehensive modeling assessment of the various processes responsible for these contrasted projections, resolving this conflict and thereby improving our understanding of future land hydrology.

Quantitative evaluation of skin barrier function using water evaporation time related to transepidermal water loss.

Transepidermal water loss (TEWL) is often used as an index for skin barrier function. The skin barrier tester, SBT-100 (Rousette Strategy Inc), measures the TEWL, water evaporation time, and time constant by contacting the skin and diffusing water into the closing measurement chamber. However, the relationship between the TEWL and time constant has not been sufficiently investigated. This study involved analyzing the underlying measurement principle and obtaining data through two experiments. The TEWL and time constant were measured using SBT-100. Experiment 1 produced a simple simulation model for continuous water evaporation from the skin using a moisture-permeable film. In experiment 2, four skin sites of 43 healthy volunteers were examined from May to September 2018. In experiment 1, the TEWL increased and time constant decreased, following an increase in humidity in the external environment. Both parameters demonstrated significant negative correlation (drying: ρ=-0.832, p<0.001). For the 43 healthy volunteers who participated in experiment 2, their TEWL increased and time constant decreased in summer. For all skin measurement sites, both data demonstrated significant negative correlation (forehead: ρ=-0.909, p<0.001; back of the left hand: ρ=-0.829, p<0.001; left lateral elbow: ρ=-0.896, p<0.001; left lateral malleolus: ρ=-0.865, p<0.001). Results indicated that the time constant is significantly correlated with TEWL. Furthermore, the time constant can be used as a parameter for evaluating skin barrier function.

Automated patient-robot assignment for a robotic rehabilitation gym: a simplified simulation model

BackgroundA robotic rehabilitation gym can be defined as multiple patients training with multiple robots or passive sensorized devices in a group setting. Recent work with such gyms has shown positive rehabilitation outcomes; furthermore, such gyms allow a single therapist to supervise more than one patient, increasing cost-effectiveness. To allow more effective multipatient supervision in future robotic rehabilitation gyms, we propose an automated system that could dynamically assign patients to different robots within a session in order to optimize rehabilitation outcome.MethodsAs a first step toward implementing a practical patient-robot assignment system, we present a simplified mathematical model of a robotic rehabilitation gym. Mixed-integer nonlinear programming algorithms are used to find effective assignment and training solutions for multiple evaluation scenarios involving different numbers of patients and robots (5 patients and 5 robots, 6 patients and 5 robots, 5 patients and 7 robots), different training durations (7 or 12 time steps) and different complexity levels (whether different patients have different skill acquisition curves, whether robots have exit times associated with them). In all cases, the goal is to maximize total skill gain across all patients and skills within a session.ResultsAnalyses of variance across different scenarios show that disjunctive and time-indexed optimization models significantly outperform two baseline schedules: staying on one robot throughout a session and switching robots halfway through a session. The disjunctive model results in higher skill gain than the time-indexed model in the given scenarios, and the optimization duration increases as the number of patients, robots and time steps increases. Additionally, we discuss how different model simplifications (e.g., perfectly known and predictable patient skill level) could be addressed in the future and how such software may eventually be used in practice.ConclusionsThough it involves unrealistically simple scenarios, our study shows that intelligently moving patients between different rehabilitation robots can improve overall skill acquisition in a multi-patient multi-robot environment. While robotic rehabilitation gyms are not yet commonplace in clinical practice, prototypes of them already exist, and our study presents a way to use intelligent decision support to potentially enable more efficient delivery of technologically aided rehabilitation.

Current Ratio and Stability Issues of Electronically Enhanced Current Transformer Stimulated by Stray Inter-Winding Capacitance and Secondary-Side Disturbance Voltage.

Electronically enhanced current transformers (EECT) have gained much interest in power quality assessment. Their magnitude and phase angle error, which mainly relates to the properties of the ferromagnetic materials used, the impedance of the secondary load, and the inter-turns capacitance, are thoroughly analyzed. In contrast, the capacitance between the windings, i.e., inter-winding capacitances and their limiting effects on EECT operation, are rarely analyzed in detail—in particular, no details on the control design of the assisting electronic unit, its tuning recommendations, or both are provided. In this paper, the capacitive coupling between indication and compensating winding of EECT with simplified feedthrough construction is analyzed thoroughly in terms of current ratio error and stability of the implemented configuration of the trans-conductance amplifier. The preliminary assumption about the adverse effect of the inter-winding capacitance shunting both ends of the original amplifier, composed of two series-connected inverting amplifier stages, was confirmed and resolved within a modified amplifier with the help of a simplified simulation model and was experimentally proven with measurements on a custom-built EECT prototype. Furthermore, the analyzed phenomena were linked to trans-conductance amplifier parameters, explicitly with its compensating networks, and summarized in their design guidelines. Throughout the paper, the EECT features obtained with original and modified amplifier designs are compared with the plain composite current transformer to demonstrate the benefits of the modified amplifier, especially its robustness against inter-winding capacitance variations.

The advantage of self-protecting interventions in mitigating epidemic circulation at the community level

Protecting interventions of many types (both pharmaceutical and non-pharmaceutical) can be deployed against the spreading of a communicable disease, as the worldwide COVID-19 pandemic has dramatically shown. Here we investigate in detail the effects at the population level of interventions that provide an asymmetric protection between the people involved in a single interaction. Masks of different filtration types, either protecting mainly the wearer or the contacts of the wearer, are a prominent example of these interventions. By means of analytical calculations and extensive simulations of simple epidemic models on networks, we show that interventions protecting more efficiently the adopter (e.g the mask wearer) are more effective than interventions protecting primarily the contacts of the adopter in reducing the prevalence of the disease and the number of concurrently infected individuals (“flattening the curve”). This observation is backed up by the study of a more realistic epidemic model on an empirical network representing the patterns of contacts in the city of Portland. Our results point out that promoting wearer-protecting face masks and other self-protecting interventions, though deemed selfish and inefficient, can actually be a better strategy to efficiently curtail pandemic spreading.

Human-Plant Coevolution: A modelling framework for theory-building on the origins of agriculture

The domestication of plants and the origin of agricultural societies has been the focus of much theoretical discussion on why, how, when, and where these happened. The 'when' and 'where' have been substantially addressed by different branches of archaeology, thanks to advances in methodology and the broadening of the geographical and chronological scope of evidence. However, the 'why' and 'how' have lagged behind, holding on to relatively old models with limited explanatory power. Armed with the evidence now available, we can return to theory by revisiting the mechanisms allegedly involved, disentangling their connection to the diversity of trajectories, and identifying the weight and role of the parameters involved. We present the Human-Plant Coevolution (HPC) model, which represents the dynamics of coevolution between a human and a plant population. The model consists of an ecological positive feedback system (mutualism), which can be reinforced by positive evolutionary feedback (coevolution). The model formulation is the result of wiring together relatively simple simulation models of population ecology and evolution, through a computational implementation in R. The HPC model captures a variety of potential scenarios, though which conditions are linked to the degree and timing of population change and the intensity of selective pressures. Our results confirm that the possible trajectories leading to neolithisation are diverse and involve multiple factors. However, simulations also show how some of those factors are entangled, what are their effects on human and plant populations under different conditions, and what might be the main causes fostering agriculture and domestication.

Comprehensive Comparison of Hybrid Cooling of Thermal Power Generation with Airside Serial and Parallel Heat Exchange

Natural draft hybrid cooling (NDHC) for thermal power generating units is proposed to achieve a balance of energy and water consumption for arid areas. This study examines the two main design forms of hybrid cooling with airside in serial and parallel heat exchange based on the same tower shell and heat transfer areas. Taking full consideration of the thermal cycle of the power generating unit, simplified simulation models for different cooling systems are established to show the influences of ambient conditions and marketing factors. Results show that both the hybrid cooling designs have a better cooling efficiency than either dry cooling or wet cooling. Expanded inlet areas of hybrid cooling in the parallel heat exchange design bring high heat transfer performance. As for the serial design, the higher temperature of the air at the outlet of the dry section maintains a larger airside mass flow rate, obtaining a high-efficient cooling system. The hybrid cooling in the serial design type relies more on the heat transfer performance of the wet section and is more sensible to ambient humidity, while the performance of hybrid cooling in the parallel design mainly depends on the dry section and is more easily affected by ambient temperature. Considering the unit cost variations of coal and water treatment, hybrid cooling in the parallel design has a wider range of applications compared with the serial design. With the growth in coal cost, there exist more benefits with the serial design.

An inner boundary condition of moisture diffusion model for simulating transient nonlinear moisture transport in Chinese fir

This paper proposed an inner boundary condition of moisture diffusion model for simulating transient nonlinear moisture transport of Chinese fir (Cunninghamia lanceolata). The inner boundary condition is serviced for simulate the moisture diffusion of multi-layer boards and is mainly used for the boundary conditions inside component, which presents the diffusion of moisture between wood and its adjacent wood. Furthermore, the established simulation model contains fiber orientation information and is used to simulate the moisture diffusion under different boundary conditions, which considers the constrained boundary. Simulation of simple boundary condition models and the proposed inner boundary condition model under different boundary conditions for multilayer board specimen exposed to constant temperature and constant humidity with a known initial moisture content, and the model was then validated in a laboratory climate chamber. Different from the simple boundary condition model the direct error of the proposed inner boundary model was less than 2% (moisture content), which indicates the proposed inner boundary condition could improve the accuracy of moisture diffusion model. The results show that the inner boundary condition model can comprehensively analyze the transient nonlinear moisture transfer process in different fiber directions with high accuracy.