Simple Simulation Model Research Articles

Development of a 3-D quasi-steady-state tyre model for on-road and off-road vehicle dynamics simulations: Part II - off-road rigid wheel model

This study presents the development of a simplified brush-based tyre model for on-road simulation, together with a simplified off-road wheel/tyre model that has the capability to revert back to on-road trend of behaviour on firmer soils. The on-road tyre model is developed based on empirical data collected by NHSTA, while the off-road tyre model is developed based on observations of experimental data and photographic evidence collected by various terramechanics researchers within the last few decades. Using theoretical analysis and empirical data, the tyre deformation geometry is determined to establish the tractive forces in off-road operation. The first step of any off-road vehicle is to model the condition where the soil is much more deformable than the tyre, where the tyre can be modelled as a rigid wheel. This study explores the development of the rigid wheel mode of the model, using dry sandy terrain, an example of extremely deformable soil. This paper is the second of three papers on the modelling of tyres for both on and off-road operations.

PREDICTING PLANT-AVAILABLE NITROGEN FROM ORGANIC AMENDMENTS IN THE SECOND YEAR AFTER APPLICATION

First-year plant-available N (PAN) release from organic amendments has received considerable study, but longer-term data are lacking. Our objectives were to: (i) measure the percentage of total N available to a sweet corn crop in the second year after organic amendment application, (ii) determine whether Yr 2 PAN predictions need to be amendment-specific, and (iii) evaluate laboratory incubation methods for PAN estimation vs. field PAN. PAN released from 8 composts and 4 uncomposted organic amendments was measured at two field locations (sandy loam and silt loam soils). Organic amendments were applied at field sites in the spring of Yr 1, supplying an average of 570 kg N/ha at an application rate of 30 Mg/ha. Data reported here were collected in Yr 2. Sweet corn (Zea mays ‘Golden Jubilee’) was planted at field sites to estimate PAN using an N fertilizer equivalency approach. In the laboratory, PAN was measured as inorganic N accumulated during a 7-d anaerobic incubation at 40°C, or a 110-d aerobic incubation at 22°C. Laboratory PAN was calculated using the difference method (PAN for amended soil vs. PAN for no amendment control soil). As a percentage of Yr 1 total N input, Yr 2 PAN was 7% in field trials, 7% for aerobic incubation (110-d, 22°C), and 3% for anaerobic incubation (7-d, 40°C). In the 110-d aerobic incubation, PAN release was linear across time, with 3% of total N input mineralized per thousand Nmin degree days (0°C base). The linear rate of PAN accumulation observed in aerobic lab incubations, coupled with the finding that Yr 2 PAN was strongly related to quantity of Yr 1 N input (across all amendments) suggests that relatively simple computer simulation models can be used to predict Yr 2 PAN for a wide variety of organic inputs.

Simple Circuit Simulation Models for Eddy Current in Magnetic Sheets and Wires

Simple Circuit Simulation Models for Eddy Current in Magnetic Sheets and Wires

Synthesis of Ag/Ag<sub>2</sub>S Nanoclusters Resistive Switches for Memory Cells

Resistive switching Ag/Ag2S nanoclusters were formed by sulphidation of melting-dispersed thin and continuous Ag films. The morphology, structure and electrical properties of the prepared clusters were characterized by scanning (SEM), transmitting electron (TEM), scanning resistance microscopes (SRM) and Raman scattering. Hysteretic resistive switching behavior was observed in the samples that were studied with ON/OFF switching voltage equal to 8 - 10 V respectively. Simple empirical numerical simulation model, based on Deal-Grove model assumptions and mechanisms, for silver nanoclusters sulphidation process, was proposed.

Modeling the Inference between Upstream Inflow Hydrographs and Downstream Flooded Areas in a Reservoir Driven System

Management of a river imposes a task for several institutional levels in every part of the world, especially when reservoirs are the main flow drivers. The research presented herein shows how management of the flow in a reservoir driven system can be modeled by using an inference simulation model between two sets of variables, as an alternative to an approach based on an optimization model. The first selected variables are the explanatory ones, which refers to the relation between the operation of reservoirs and the input hydrographs to each of the considered reservoirs. The second set of variables are descriptive and refers to the resulting flooding hydrograph at a hydrological station located downstream of the reservoir network. The Yellow River, in China, is chosen to demonstrate the concept, however the methodology can be applied in practice for any reservoir driven system. In the mid stream of the Yellow River, a system of four reservoirs was built to manage flooding, using daily information and taking daily decisions. The proposed method uses a simplified simulation model of the actual reservoir operation to determine a multiple linear regression model between the set of explanatory and descriptive variables. The set of explanatory variables is very large and the demonstration is done on a selected subset of variables. Each selection of an explanatory variable is based on a correlation analysis with respect to the original set. Analysis of the model results shows that the reduction of the number of variables does not decrease the model fitness and robustness.

A Fano cavity test for Monte Carlo proton transport algorithms

In the scope of reference dosimetry of radiotherapy beams, Monte Carlo (MC) simulations are widely used to compute ionization chamber dose response accurately. Uncertainties related to the transport algorithm can be verified performing self-consistency tests, i.e., the so-called "Fano cavity test." The Fano cavity test is based on the Fano theorem, which states that under charged particle equilibrium conditions, the charged particle fluence is independent of the mass density of the media as long as the cross-sections are uniform. Such tests have not been performed yet for MC codes simulating proton transport. The objectives of this study are to design a new Fano cavity test for proton MC and to implement the methodology in two MC codes: Geant4 and PENELOPE extended to protons (PENH). The new Fano test is designed to evaluate the accuracy of proton transport. Virtual particles with an energy of E0 and a mass macroscopic cross section of Σρ are transported, having the ability to generate protons with kinetic energy E0 and to be restored after each interaction, thus providing proton equilibrium. To perform the test, the authors use a simplified simulation model and rigorously demonstrate that the computed cavity dose per incident fluence must equal ΣE0ρ, as expected in classic Fano tests. The implementation of the test is performed in Geant4 and PENH. The geometry used for testing is a 10 × 10 cm(2) parallel virtual field and a cavity (2 × 2 × 0.2 cm(3) size) in a water phantom with dimensions large enough to ensure proton equilibrium. For conservative user-defined simulation parameters (leading to small step sizes), both Geant4 and PENH pass the Fano cavity test within 0.1%. However, differences of 0.6% and 0.7% were observed for PENH and Geant4, respectively, using larger step sizes. For PENH, the difference is attributed to the random-hinge method that introduces an artificial energy straggling if step size is not small enough. Using conservative user-defined simulation parameters, both PENH and Geant4 pass the Fano cavity test for proton transport. Our methodology is applicable to any kind of charged particle, provided that the considered MC code is able to track the charged particle considered.

A wire-form emitter metal–insulator–semiconductor tunnel junction

Physical effects arising due to change of configuration of a MIS system from planar to cylindrical, are theoretically analyzed. Attention is paid to the voltage partitioning and all the components of tunneling current. A simple simulation model is developed enabling prediction of the band diagram details and calculation of the currents. The trends expected with decreasing system radius are elucidated. Cylindrical geometry can be faced with when quantum wire is used as an electron emitter. Similar form may also be roughly attributed to an edge region of conventional MIS capacitors.

The Impact of the Personal Direct Income Tax on the Romanian Agriculture. A critical analysis.

After several years in which the individual producers were except from tax payment for the personal agricultural income, in 2013 a new special direct tax was introduced in Romania. The paper aims to deepen the economic understanding of the potential consequences of this tax. It proposes a simple micro simulation model used to evaluate the tax revenue obtained by the state budget. It also investigates the potential outcomes at the farm level using different scenarios. The material is represented by the official statistic issued about the Romanian individual farms (number, size, livestock, and economic orientation). Results suggest that more than 900 thousands of individual farms will pay it which will increase the administrative tax-cost. The lack of farmer education and information is negative correlated with its effectiveness. The tax revenue is low, but it can bring positive results in decreasing the untaxed economy. For the subsistence and semi-subsistence individual producers the tax will act as negative incentives for crop-pattern diversification and farm-size increase. Thus it has to be fallow by agriculture policy measure such as to sustain the small individual farms in their effort of becoming economic self-sufficient.

Modified fish-bone model: A simplified MDOF model for simulation of seismic responses of moment resisting frames

This paper presents a simplified Multi-Degree-Of-Freedom (MDOF) model through modification of fish-bone model (or generic frame). Modified Fish-Bone (MFB) model is developed through three enhancements: (i) the moment of inertia for half-beams is reduced slightly to modify the assumption of equal rotation at each story joints, (ii) a number of truss elements are inserted to the fish-bone model to simulate flexural deformation of moment frames due to axial elongation and contraction of columns, and (iii) moment–rotation relationship of representative rotational springs is supposed to be bilinear instead of trilinear in order to consider simultaneous yielding at both ends of the beam in moment frames. The proposed model is evaluated with respect to nonlinear dynamic analysis results of three classic moment resisting frames subjected to 94 records of FEMA-440 ground motion data set. Moreover, the adequacy of this model is compared with the fish-bone model and two predictors of nonlinear seismic demand. The statistical study of predicted interstory drift demonstrates the superiority of the proposed model over the fish-bone model and both seismic demand predictors.

Assessment of energy production from photovoltaic modules integrated in typical shading devices

Abstract This paper presents the results of three methods that measure energy produced by photovoltaic (PV) modules integrated in various external opaque shadings of typical office buildings in Greece. These methods are related to the comparison of energy production results by three different models: a simple energy computer simulation model that uses the theoretical average PV efficiency of 12%, a more complete computer simulation model using detailed equations (using either theoretical or real PV Market products), and real PV installations. The paper addresses the problem of designing efficient shading devices for buildings. Each examined method refers to a different design stage according to the level of information that is available to the designer. The results showed that the simple simulation and the more elaborated models have similar performance for most of the shading devices, apart from those with a complicated geometry. Moreover, the complete model that uses parameters of PV modules already available on the market can provide results of energy production even for complicated geometries. It is also concluded that the real PV installations produce results very close to the theoretical average PV efficiency of 12%.

Improvement of Dynamic Models of Photovoltaic Arrays

The nonlinear characteristic of photovoltaic cell following changes of irradiation and ambient temperature must be solved to research solar energy deeply and to utilize it high-efficiently. For building simple and practical dynamic simulation model and seeking after control strategy for raising out-power, a modified dynamic model of photovoltaic array is developed based on the physical model of photovoltaic cell, in which the voltage and current coefficients about ambient temperature and irradiation are introduced. By the model with stronger applicability and generality, the photovoltaic array I-V characteristic can be simulated arbitrarily with changes of irradiationambient temperaturephotovoltaic module parameter and its combination. The validity of the model is verified by all of the simulation results under Matlab/Simulink.

Correcting the NOAA/MEPED energetic electron fluxes for detector efficiency and proton contamination

The Medium Energy Proton and Electron Detector (MEPED) instruments onboard the NOAA/POES satellites have provided a valuable long‐term database of low‐altitude energetic particle observations spanning from 1978 to present. Here we study the instrumental problems of the NOAA/MEPED electron detectors and present methods to correct them. It is well known that the MEPED electron detectors are contaminated by protons of certain energy range. Using the recently corrected MEPED proton fluxes, we are now able to reliably remove this contamination. Using a simple simulation model to estimate the response of the MEPED electron detectors to incoming electrons and protons, we show that efficiencies of (Space Environment Monitors) SEM‐1 and SEM‐2 versions of the detectors have large differences due to different detector designs. This leads to a systematic difference between the SEM‐1 and SEM‐2 measurements and causes a significant long‐term inhomogeneity in measured MEPED electron fluxes. Using the estimated efficiencies, we remove the proton contamination and correct the electron measurements for nonideal detector efficiency. We discuss the entire 34 year time series of MEPED measurements and show that, on an average, the correction affects different energy channels and SEM‐1 and SEM‐2 instruments differently. Accordingly, the uncorrected electron fluxes and electron spectra are severely distorted by nonideal detector efficiency and proton contamination, and their long‐term evolution is misrepresented without the correction. The present correction of the MEPED electron fluxes over the whole interval of NOAA/POES measurements covering several solar cycles is important for long‐term studies of, e.g., magnetospheric dynamics, solar activity, ionospheric research, and atmospheric effects of energetic electrons.

Mesoscopic supply chain simulation

This paper reviews and compares existing approaches for supply chain modeling and simulation and applies the mesoscopic modeling and simulation approach using the simulation software MesoSim, an own development. A simplified real-world supply chain example is modeled with discrete event, mesoscopic and system dynamics simulation. The objective of the study is to compare the process of model creation and its validity using each approach. The study examines advantages of the mesoscopic approach for the simulation. Major benefits of the mesoscopic approach are that modeling efforts are balanced with the necessary level of detail and facilitate quick and simple model creation and simulation.

Development of Two-Dimensional Simple Simulation Model and Evaluation of Discharge Ability for Water Discharge of Firefighting

Development of Two-Dimensional Simple Simulation Model and Evaluation of Discharge Ability for Water Discharge of Firefighting

Utilization Mathematical and Physical Models Derived Therefrom Real-Time Models for the Optimization of Heating Processes

Abstract Heating of materials is energy and costly operations. On those reasons optimization is highly desirable. One of the possible solutions to optimize heating in real time is to use a large number of fast simulations on the basis of them the optimization algorithms have chosen the most appropriate option of the heating control. This solution implies the use of extremely fast but sufficiently accurate simplified mathematical models of heating, the structure and parameters of them are defined based on accurate modelling using computationally intensive but slower classical mathematical-physical models. Based on the operating data of the reheating furnace was build an accurate model of heating. Using the simplified model simulation of heating was done with different heating conditions with downtime during heating. Proposed algorithms including the simulations show that the proposed strategy leads to verifiable savings during heating.

Flat lens for pulse focusing of elastic waves in thin plates

The ability of left-handed materials to overcome the diffraction limit was first considered as one of the most exciting and challenging outcomes of the negative refraction concept. Flat lens focusing of elastic waves is, however, a challenge. We demonstrate broadband focusing of elastic waves at 10 kHz carrier frequency, below the first stop band, in a 45°-tilted square array of circular air holes perforated in a Duraluminium thin plate. By adjusting the relative thickness of the outer plate we achieve large-angle negative refraction with diffraction-limited lateral resolution. We find good agreement with a simple beam-lattice model and finite-difference time-domain simulations.

Numerical Analysis of the Exterior Explosion Effects on the Buildings with Barriers

Generation and transmission of blast waves in real terrains is of major importance for risk analysis procedures involving accidental explosion scenarios. This paper aims to show the approach to addressing air pressure waves from explosions using empirical formulas and compare them with numerical computations, which is solved using the computational program AUTODYN. Simulation of a simple model of the building is presented in the interaction with the air pressure wave caused by the explosion, which is initiated at a distance of 30 meters from the front of the building. The explosion process will be shown in 2D axial plane which is then remapped into Eulerian multi-material 3D space using the interaction of the rigid obstacles. The weight of 1000 kg TNT charge is used, which is located one meter above the ground and represents the explosive placed in a car in accordance with FEMA requirements. The effects of the protection structures are investigated.

On the potential of δ18O and δ15N to assess N2O reduction to N2 in soil

SummaryEnhancing microbial reduction of the potent greenhouse gas nitrous oxide (N2O) to N2 could be a promising strategy to mitigate emissions from soils, but N2O reduction rates are currently neither well understood nor quantified. It has been suggested that the importance of N2O reduction to N2 could be estimated from relationships between δ18O and δ15N when N2O production and reduction occur simultaneously. We assessed the robustness of such relationships by using simple simulation models and experimental data for various scenarios, including open versus closed system isotope dynamics and collection of N2O fluxes over time with and without refreshing the headspace between sampling. We found that relationships between δ18O and δ15N vary dramatically with experimental conditions (such as headspace gas concentration and sampling scheme) and open versus closed system isotope dynamics, irrespective of N2O reduction rate. Therefore, we conclude that the simple relationships between δ18O and δ15N currently used are not robust indicators of N2O reduction to N2 and strongly discourage graphical interpretations of δ18O and δ15N to determine N2O reduction. We recommend the development of more advanced process‐based isotope models that take into account open versus closed system isotope dynamics, experimental conditions, isotope values of precursors and other biogeochemical controls on δ15N and δ18O of N2O to estimate N2O reduction rates more reliably from natural abundance isotope values of N2O.

In vivo effects of microcystins and complex cyanobacterial biomass on rats (Rattus norvegicus var. alba): Changes in immunological and haematological parameters

Toxic cyanobacteria represent a serious health and ecological problem in drinking and recreational waters worldwide. Some previous toxicological studies investigated effects of isolated microcystins on laboratory rodents including mice and rats. However, much less attention has been paid to more realistic exposure situations such as the effects of MCs accumulated in food. The objectives of the present study were to provide a simple model simulation of the food chain in order to evaluate impacts of microcystins (MCs) on rat immune and haematologicalparameters. Impacts of feeding experimental rats with a diet containing fish meat with and without microcystins and complex toxic biomass have been studied during a 28 day exposure. Red blood cell parameters (RBC counts, haematocrit values, MCH, MCV and MCHC) showed significant differences in experimental groups (p ≤ 0.05, p ≤ 0.01) in comparison with the control group. We also detected an immunomodulatory effect in the experimental groups. NK cells and γδ+ T lymphocytes were significantly increased in peripheral blood in the group exposed to isolated microcystin in the food. Significant change in the ratio of CD4+ and CD8+ cells (increase of CD4+ and a drop in CD8+) was found in the group with added cyanobacterial biomass with low concentration of MCs. The greatest changes in lymphoid organs were observed in the same groups. There was an increase of spleen subpopulations of γδ+ T lymphocytes as well as of IgM+ lymphocytes (B lymphocytes) and CD8+ T lymphocytes. Indeed, the modulation of CD4+ and CD8+ of peripheral lymphocytes was associated with similar changes in thymic lymphocytic subpopulations. In summary, food containing fish meat with considerable doses of microcystins (or toxic cyanobacterial biomass) induces significant changes in RBC parameters and influence preferably innate part of the immune system represented by NK cells and by gamma-delta T cells, which are known to play role as a bridge between adaptive and innate immune response.

The Chicken Aorta as a Simulation-Training Model for Microvascular Surgery Training

As a technically demanding skill, microsurgery is taught in the lab, in the form of a course of variable length (depending on the centre). Microsurgical training courses usually use a mixture of non-living and live animal simulation models. In the literature, a plethora of microsurgical training models have been described, ranging from low to high fidelity models. Given the high costs associated with live animal models, cheaper alternatives are coming into vogue. In this paper we describe the use of the chicken aorta as a simple and cost effective low fidelity microsurgical simulation model for training.