Simple Simulation Model Research Articles

DEVELOPMENT OF ACOUSTICAL SIMULATION MODEL FOR MUFFLER

Mufflers have been widely used to reduce the noise level emitted from various vehicles. The simple and high accuracy simulation model for muffler is highly requested by designers in evaluation stage of preliminary design. In this paper, the simulation model was developed by using SysNoise application in LMS Virtual Lab. The basic geometry of simple expansion chamber muffler was proposed for simulation and evaluation in terms of transmission loss (TL). The developed model via simulation had been verified by comparing the predicted TL of simple expansion chamber muffler with the experimental data in literature. It can be observed that simulation results have good agreement with the experimental data from literature. In addition, simulation-based muffler analysis also was conducted for parametrical studies in order to enhance the TL of muffler. As a conclusion, the computational acoustic model based on Finite Element Method (FEM) was successfully developed for prediction of TL on mufflers.

Kinematically Coupled Force Compensation – Design Principle and Control Concept for Highly-dynamic Machine Tools

Today, the dynamics, especially acceleration and jerk, of machine tools are limited in order to reduce excitations of machine structure vibrations to an acceptable level. A novel approach - the Kinematically Coupled Force Compensation (KCFC) - combines the principles of redundant axes and force compensation to further increase machines’ dynamics. In this paper, the new principle is introduced and possible control concepts are compared based on an analysis in frequency and time domain. Simulations, using a simple multi-body simulation model implemented in MATLAB/Simulink®, show, that machine structure vibrations can be reduced significantly by KCFC.

Generic framework for mining cellular automata models on protein-folding simulations.

Cellular automata model identification is an important way of building simplified simulation models. In this study, we describe a generic architectural framework to ease the development process of new metaheuristic-based algorithms for cellular automata model identification in protein-folding trajectories. Our framework was developed by a methodology based on design patterns that allow an improved experience for new algorithms development. The usefulness of the proposed framework is demonstrated by the implementation of four algorithms, able to obtain extremely precise cellular automata models of the protein-folding process with a protein contact map representation. Dynamic rules obtained by the proposed approach are discussed, and future use for the new tool is outlined.

Non-additive response of larval ringed salamanders to intraspecific density

Conditions experienced in early developmental stages can have long-term consequences for individual fitness. High intraspecific density during the natal period can affect juvenile and eventually adult growth rates, metabolism, immune function, survival, and fecundity. Despite the important ecological and evolutionary effects of early developmental density, the form of the relationship between natal density and resulting juvenile phenotype is poorly understood. To test competing hypotheses explaining responses to intraspecific density, we experimentally manipulated the initial larval density of ringed salamanders (Ambystoma annulatum), a pond-breeding amphibian, over 11 densities. We modeled the functional form of the relationship between natal density and juvenile traits, and compared the relative support for the various hypotheses based on their goodness of fit. These functional form models were then used to parameterize a simple simulation model of population growth. Our data support non-additive density dependence and presents an alternate hypothesis to additive density dependence, self-thinning and Allee effects in larval amphibians. We posit that ringed salamander larvae may be under selective pressure for tolerance to high density and increased efficiency in resource utilization. Additionally, we demonstrate that models of population dynamics are sensitive to assumptions of the functional form of density dependence.

A stochastic model for magnetic dynamics in single-molecule magnets

Hysteresis and magnetic relaxation curves were performed on double well potential systems with quantum tunneling possibility via stochastic simulations. Simulation results are compared with experimental ones using the Mn12 single-molecule magnet, allowing us to introduce time dependence in the model. Despite being a simple simulation model, it adequately reproduces the phenomenology of a thermally activated quantum tunneling and can be extended to other systems with different parameters. Assuming competition between the reversal modes, thermal (over) and tunneling (across) the anisotropy barrier, a separation of classical and quantum contributions to relaxation time can be obtained.

A Simplified Simulation Model for Predicting Radiative Transfer in Long Street Canyons under High Solar Radiation Conditions

Modeling solar radiation in street canyons is crucial to understanding the solar availability of building façades. This article describes the implementation of a simulation routine, developed in the Matlab® computer language, which is aimed at predicting solar access for building façades located in dense urban conglomerates comprising deep long street canyons, under high solar radiation conditions, typical in southern countries of Europe. Methodology is primarily based on the configuration factor theory, also aided by computer simulation, which enables to assess the interplay between the surfaces that compose the so-called street canyon. The results of the theoretical model have been cross-checked and verified by on-site measurements in two real case studies, two streets in Cadiz and Seville. The simplified simulation reproduces the shape of the curve for on-site measured values and weighted errors for the whole model do not surpass 10%, with a maximum of 9.32% and a mean values of 6.31%. As a result, a simplified predictive model that takes into account direct, diffuse and reflected solar radiation from the surfaces that enclose the canyon, has been devised. The authors consider that this research provides further improvement, as well as a handy alternative approach, to usual methods used for the calculation of available solar radiation in urban canyons, such as the Sky View Factor or the ray tracing.

A simple and efficient quasi 3-dimensional viscoelastic model and software for simulation of tapping-mode atomic force microscopy.

This paper introduces a quasi-3-dimensional (Q3D) viscoelastic model and software tool for use in atomic force microscopy (AFM) simulations. The model is based on a 2-dimensional array of standard linear solid (SLS) model elements. The well-known 1-dimensional SLS model is a textbook example in viscoelastic theory but is relatively new in AFM simulation. It is the simplest model that offers a qualitatively correct description of the most fundamental viscoelastic behaviors, namely stress relaxation and creep. However, this simple model does not reflect the correct curvature in the repulsive portion of the force curve, so its application in the quantitative interpretation of AFM experiments is relatively limited. In the proposed Q3D model the use of an array of SLS elements leads to force curves that have the typical upward curvature in the repulsive region, while still offering a very low computational cost. Furthermore, the use of a multidimensional model allows for the study of AFM tips having non-ideal geometries, which can be extremely useful in practice. Examples of typical force curves are provided for single- and multifrequency tapping-mode imaging, for both of which the force curves exhibit the expected features. Finally, a software tool to simulate amplitude and phase spectroscopy curves is provided, which can be easily modified to implement other controls schemes in order to aid in the interpretation of AFM experiments.

CEPSim: Modelling and simulation of Complex Event Processing systems in cloud environments

The emergence of Big Data has had profound impacts on how data are stored and processed. As technologies created to process continuous streams of data with low latency, Complex Event Processing (CEP) and Stream Processing (SP) have often been related to the Big Data velocity dimension and used in this context. Many modern CEP and SP systems leverage cloud environments to provide the low latency and scalability required by Big Data applications, yet validating these systems at the required scale is a research problem per se. Cloud computing simulators have been used as a tool to facilitate reproducible and repeatable experiments in clouds. Nevertheless, existing simulators are mostly based on simple application and simulation models that are not appropriate for CEP or for SP. This article presents CEPSim, a simulator for CEP and SP systems in cloud environments. CEPSim proposes a query model based on Directed Acyclic Graphs (DAGs) and introduces a simulation algorithm based on a novel abstraction called event sets. CEPSim is highly customizable and can be used to analyse the performance and scalability of user-defined queries and to evaluate the effects of various query processing strategies. Experimental results show that CEPSim can simulate existing systems in large Big Data scenarios with accuracy and precision.

Occurrence and simulation of trihalomethanes in swimming pool water: A simple prediction method based on DOC and mass balance

Trihalomethanes (THM) are the most typical disinfection by-products (DBPs) found in public swimming pool water. DBPs are produced when organic and inorganic matter in water reacts with chemical disinfectants. The irregular contribution of substances from pool visitors and long contact time with disinfectant make the forecast of THM in pool water a challenge. In this work occurrence of THM in a public indoor swimming pool was investigated and correlated with the dissolved organic carbon (DOC). Daily sampling of pool water for 26 days showed a positive correlation between DOC and THM with a time delay of about two days, while THM and DOC didn't directly correlate with the number of visitors. Based on the results and mass-balance in the pool water, a simple simulation model for estimating THM concentration in indoor swimming pool water was proposed. Formation of THM from DOC, volatilization into air and elimination by pool water treatment were included in the simulation. Formation ratio of THM gained from laboratory analysis using native pool water and information from field study in an indoor swimming pool reduced the uncertainty of the simulation. The simulation was validated by measurements in the swimming pool for 50 days. The simulated results were in good compliance with measured results. This work provides a useful and simple method for predicting THM concentration and its accumulation trend for long term in indoor swimming pool water.

A semi-dynamic heart model for UWB microwave transmission simulations and hardware evaluation

In this paper, we present a simplified semi-dynamic heart model for investigation of microwave transmission heart monitoring systems between 1.5 and 4 GHz in both simulation and measurement. We aim to validate that our proposed heart model is able to represent the heart structure at microwave frequencies by comparing our model to an accurate numerical heart model (anHM) from the ITIS foundation virtual population. Our simple numerical heart model (snHM) (simulation) and physical heart model (pHM) (measurement) are evaluated in a simplified human chest model using an UWB biomedical sensor. In simulation, the transmission parameter shows agreement with the time domain peak of −94.5 dB for the snHM and −96.4 dB in the anHM. The anHM and pHM transmission signal characteristics were then compared showing good agreement. Our heart model is able to represent the heart between 1.5 and 4.0 GHz and represents a step toward a real time dynamic heart model for hardware evaluation.

Parallel implementation of the time-evolving block decimation algorithm for the Bose–Hubbard model

A system of ultracold atoms in an optical lattice represents a powerful experimental setup for testing the fundamentals of quantum mechanics. While its microscopic interaction mechanisms are well understood, the system behavior for a moderate number of particles is difficult to simulate due to a high dimension of its many-body space. This article presents TEBDOL, a parallel implementation of the time-evolving block decimation (TEBD) algorithm that can efficiently simulate time evolution of a one-dimensional chain of atoms in optical lattices. We investigate the parallelization strategy and the strong and weak scaling with the number of processes. Program summaryProgram title: TEBDOLCatalogue identifier: AEYN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEYN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: GNU General Public License v3.0No. of lines in distributed program, including test data, etc.: 9060No. of bytes in distributed program, including test data, etc.: 54338Distribution format: tar.gzProgramming language: Common Lisp.Computer: x86-64.Operating system: Linux.Has the code been vectorized or parallelized?: Parallelized using MPIRAM: 1–64 GBClassification: 7.7.External routines: Basic Linear Algebra Subprograms (BLAS), Linear Algebra Package (LAPACK), Message Passing Interface (MPI)Nature of problem: A system of neutral atoms in an optical lattice is a many-body quantum system that can be described using the Bose–Hubbard model. Hilbert space dimensions of many-body quantum models grow exponentially with the number of particles. Simulating time evolution in the Bose–Hubbard model is therefore a hard problem even in case of a moderate number of particles.Solution method: A system state is represented by a tensor network. Its time evolution is then simulated using the time-evolving block decimation (TEBD) algorithm.Restrictions: TEBDOL is limited to one-dimensional systems. The times accessible in the simulations are restricted by the growth of entanglement in the system.Unusual features: Tensor networks in TEBDOL support a global Abelian symmetry, i.e., the program conserves the total number of particles. Models with multiple particle species are supported as well. TEBDOL is implemented in Common Lisp and can run in parallel on a computer cluster.Running time: Running time depends on the lattice size, on the number of particles, and on the maximal allowed tensor dimensions. Simulations of simple models take a few seconds on a single CPU while simulations of large and complex models can take up to a week on a cluster with hundreds of CPUs.

Impact of the Geometrical and Optical Parameters on the Performance of a Cylindrical Remote Phosphor LED

Remote phosphor light-emitting diode (LED) modules could offer advantages over intimate white phosphor converted LEDs in terms of phosphor operation temperature, light extraction efficiency, and angular color uniformity. Existing commercial devices show a large variety with respect to the dimensions of the mixing cavity, which raises a question about the optimization of the topology. A simplified simulation model applying a two-wavelength approach and considering the remote phosphor as one virtual surface to which three bidirectional scattering distribution functions are attributed (respectively, describing the blue–blue, blue–yellow, and yellow–yellow interactions) is developed and validated. This model has been used to analyze the impact of the cylindrical mixing cavity parameters such as the absolute reflectance, the diffuse-to-specular reflectance ratio, and the height of the mixing cavity, as well as the pitch and angular full-width at half-maximum of the LEDs on the extraction efficiency, the yellow-to-blue ratio, and the irradiance uniformity. It can be concluded that in order to increase the efficacy substantially, the recuperation of the backward emission of the converted light can only be increased by avoiding further interaction with the phosphor plate. To this extent, topologies other than cylindrical mixing cavities must be considered.

Direct evaporative passive cooling of building. A comparison amid simplified simulation models based on experimental data

Different simplified simulation models of a Passive Downdraught Evaporative Cooling tower (PDEC) were compared by using experimental data. Among these, a series of tests on a Passive Downdraught Evaporative Cooling tower (PDEC) were carried out at the SyTIn (Systems for Technology Innovation) Laboratory of the Department of Architecture and Design, Politecnico di Torino. In addition, other monitored databases were taken from literature and used as input data for the simplified models. The collected inlet airflow data were used for calculating predicted outlet airflow values by using four equations and a software from literature.The comparison of those outlet airflow data allowed for assessing the effectiveness and the accuracy of the analysed simplified methods, which are also used for simulating the PDEC tower in several dynamic simulation software such as DesignBuilder coupled with EnergyPlus. The presented results could help designers in choosing amid different calculation models.

A Few Insights on Inequality Derived from Simulation

I use a simple computer simulation model to gain insights on the nature of wealth inequality. Two testable predictions come out of the simulations: economies with higher tax rates and lower volatility should have lower inequality levels, all else constant. Another important feature of the model is that even moderate capital gains tax rates seem enough to prevent inequality from heading to one, as measured by the Gini coefficient. Tax rates and volatility are the two main drivers for long run inequality levels but, depending on initial conditions, convergence can take quite a long time.

Spatial Structure of Evolutionary Models of Dialects in Contact.

Phylogenetic models, originally developed to demonstrate evolutionary biology, have been applied to a wide range of cultural data including natural language lexicons, manuscripts, folktales, material cultures, and religions. A fundamental question regarding the application of phylogenetic inference is whether trees are an appropriate approximation of cultural evolutionary history. Their validity in cultural applications has been scrutinized, particularly with respect to the lexicons of dialects in contact. Phylogenetic models organize evolutionary data into a series of branching events through time. However, branching events are typically not included in dialectological studies to interpret the distributions of lexical terms. Instead, dialectologists have offered spatial interpretations to represent lexical data. For example, new lexical items that emerge in a politico-cultural center are likely to spread to peripheries, but not vice versa. To explore the question of the tree model’s validity, we present a simple simulation model in which dialects form a spatial network and share lexical items through contact rather than through common ancestors. We input several network topologies to the model to generate synthetic data. We then analyze the synthesized data using conventional phylogenetic techniques. We found that a group of dialects can be considered tree-like even if it has not evolved in a temporally tree-like manner but has a temporally invariant, spatially tree-like structure. In addition, the simulation experiments appear to reproduce unnatural results observed in reconstructed trees for real data. These results motivate further investigation into the spatial structure of the evolutionary history of dialect lexicons as well as other cultural characteristics.

A simplified mathematical model for transient simulation of thermal performance and energy assessment for active facades

The extended use of double skin façade (DSF) in different kinds of buildings imposes HVAC (Heating Ventilation Air Conditioning) designers to use quick and accurate software to help in taking the right decisions related to energy consumption and thermal comfort. The lack of such methods was the motive to present this paper. Validation of a simplified mathematical model for dynamic simulation of the thermal performance of DSF was presented by comparing results with another detailed simulation model DIGITHON, for a complete year. Moreover the mathematical model was developed to calculate thermal energy due to convection losses from outer facade layer, solar gains and internal loads. A more detailed comparison of energy consumption at different climatic conditions of four cities in Europe has been shown. Implementation of the simplified model in thermo-active-building-system-(TABS) also was illustrated, and how such a model could be useful in one of four methods mentioned in standard ISO-11885-4 to predict heat transfer on TABS. This particular method needs the solar gains and losses due to transmission determined with a constant room temperature by another software which the mathematical model could be implemented in.

A simplified and efficient hybrid finite element model (HYMOD) for non-linear 3D simulation of RC structures

Purpose– The purpose of this paper is to present a simplified hybrid modeling (HYMOD) approach which overcomes limitations regarding computational cost and permits the simulation and prediction of the nonlinear inelastic behavior of full-scale RC structures.Design/methodology/approach– The proposed HYMOD formulation was integrated in a research software ReConAn FEA and was numerically studied through the use of different numerical implementations. Then the method was used to model a full-scale two-storey RC building, in an attempt to demonstrate its numerical robustness and efficiency.Findings– The numerical results performed demonstrate the advantages of the proposed hybrid numerical simulation for the prediction of the nonlinear ultimate limit state response of RC structures.Originality/value– A new numerical modeling method based on finite element method is proposed for simulating accurately and with computational efficiency, the mechanical behavior of RC structures. Currently 3D detailed methods are used to model single structural members or small parts of RC structures. The proposed method overcomes the above constraints.

Field-direction control of the type of charge carriers in nonsymmorphicIrO2

In the quest for switching of the charge carrier type in conductive materials, we focus on nonsymmorphic crystals, which are expected to have highly anisotropic folded Fermi surfaces due to the symmetry requirements. Following simple tight-binding model simulation, we prepare nonsymmorphic IrO2 single-crystalline films with various growth orientations by molecular beam epitaxy, and systematically quantify their Hall effect for the corresponding field directions. The results clearly demonstrate that the dominant carrier type can be intrinsically controlled by the magnetic field direction, as also evidenced by first-principles calculations revealing nontrivial momentum dependence of the group velocity and mass tensor on the folded Fermi surfaces and its anisotropic nature for the field direction.

Numerical simulations of internal wave generation by convection in water.

Water's density maximum at 4°C makes it well suited to study internal gravity wave excitation by convection: an increasing temperature profile is unstable to convection below 4°C, but stably stratified above 4°C. We present numerical simulations of a waterlike fluid near its density maximum in a two-dimensional domain. We successfully model the damping of waves in the simulations using linear theory, provided we do not take the weak damping limit typically used in the literature. To isolate the physical mechanism exciting internal waves, we use the spectral code dedalus to run several simplified model simulations of our more detailed simulation. We use data from the full simulation as source terms in two simplified models of internal-wave excitation by convection: bulk excitation by convective Reynolds stresses, and interface forcing via the mechanical oscillator effect. We find excellent agreement between the waves generated in the full simulation and the simplified simulation implementing the bulk excitation mechanism. The interface forcing simulations overexcite high-frequency waves because they assume the excitation is by the "impulsive" penetration of plumes, which spreads energy to high frequencies. However, we find that the real excitation is instead by the "sweeping" motion of plumes parallel to the interface. Our results imply that the bulk excitation mechanism is a very accurate heuristic for internal-wave generation by convection.

Simplified simulation model of continuously transposed cable for linear and nonlinear buckling analysis

Continuously transposed cable (CTC) is a multistranded conductor mainly for application in power transformers. As its structure is complicated a simplified simulation model and an easy analytic model for the buckling analysis of transformer coils are investigated in this paper. In the simplified models the transposition of the strands is neglected leading to an easy rotation symmetric cross section. These simplified models are compared to detailed models using finite element analysis (FEA) based linear and nonlinear buckling simulations. Furthermore analytical approaches are adopted from the buckling-behavior of a circular arch for the use with CTCs. All models are compared with respect to their critical buckling load for some typical winding and CTC dimensions varying between 11 to 41 strands. The maximum deviation between detailed and simplified FEA based CTC models for both linear and nonlinear buckling analysis lies below 13%. The deviations for the analytic approaches are with a maximum of 22% higher but serve to verify the trends deduced from the simulation results.