Simple Simulation Model Research Articles

Simulation Model of Transmitted X-Rays in Polycapillary Optics for TES Microcalorimeter EDS System on Scanning Transmission Electron Microscope

We created a simple simulation model of transmitted X-rays in polycapillary optics for improved understanding of the transmission characteristics and to aid in the design of the geometrical parameters of the polycapillary optics. New polycapillary optics for a 64-pixel array transition-edge sensor (TES) microcalorimeter energy-dispersive spectrometer system that was installed in a scanning transmission electron microscope (STEM) were developed using the simulation model. The characteristic X-rays that are emitted from the STEM specimen were transmitted and focused on the pixel array TES microcalorimeter by the polycapillary optics. The experimental X-ray transmission characteristics of the manufactured polycapillary optics agreed with the simulated results.

Nonadiabatic ponderomotive effects in photoemission from nanotips in intense midinfrared laser fields

Transient near fields around metallic nanotips drive many applications, including the generation of ultrafast electron pulses and their use in electron microscopy. We have investigated the electron emission from a gold nanotip driven by midinfrared few-cycle laser pulses. We identify a low-energy peak in the kinetic energy spectrum and study its shift to higher energies with increasing laser intensities from 1.7 to $8.9\ifmmode\times\else\texttimes\fi{}{10}^{11}\phantom{\rule{0.28em}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$. The experimental observation of the upshift of the low-energy peak is compared to a simple model and numerical simulations, which show that the decay of the near field on a nanometer scale results in nonadiabatic transfer of the ponderomotive potential to the kinetic energy of emitted electrons and in turn to a shift of the peak. We derive an analytic expression for the nonadiabatic ponderomotive shift, which, after the previously found quenching of the quiver motion, completes the understanding of the role of inhomogeneous fields in strong-field photoemission from nanostructures.

Enhancing a tsunami evacuation simulation for a multi-scenario analysis using parallel computing

The numerical investigation of tsunami evacuation is becoming a major way to assess the potential evacuation risks and consider countermeasures, but it has been mostly limited to GIS-based static analysis or macroscopic agent-based modelling due to the costs of large-scale simulations. In this paper, we propose a simplified force-based evacuation simulation model and an easy-to-implement parallelization strategy for a large-scale microscopic tsunami evacuation simulation and demonstrate its applications in an actual urban environment. First, the simulation performance was verified and validated against experimental and observational results regarding basic pedestrian movement. The test results qualitatively and quantitatively showed good agreement with real pedestrian movements. The model was then applied to a case of tsunami evacuations in Kesennuma City, where the 2011 Tohoku tsunami caused devastating damage. The model was successfully scaled up to provide urban-scale characterization. In this application, the developed simulator was implemented by a hybrid MPI/OpenMP parallelized computing technique. By utilizing the proposed model with parallel computing, we achieved an urban-scale microscopic evacuation simulation five times faster than real-time and a stochastic simulation to evaluate the uncertainty in the evacuation simulation.

RETRACTED: Simulating peanut (Arachis hypogaea L.) growth and yield with the use of the Simple Simulation Model (SSM)

Abstract The use of crop simulation models for interpreting experiments and analyzing production systems in different management and environmental conditions is common in the literature. In this study, parameterization and evaluation of the Simple Simulation Model (SSM) for the prediction of peanut ( Arachis hypogaea L.) growth and yield was conducted for the first time. Data from different field experiments from Astaneh Ashrafieh of northern Iran were used for coefficient estimation and model evaluation for the Virginia-type peanut variety North Carolina 2 (cv. NC2). After estimation of genetic parameters, the model was tested using independent data. The SSM simulated peanut growth and yield with reasonable accuracy, using data of more than 10 field experiments from different environmental conditions (11 experiments in the parameterization stage and 15 experiments in the evaluation stage). Based on data of independent experiments that were not used for parameterization, the model predicted an acceptable percentage of the observed results concerning days to harvest maturity (r = 0.46, CV = 5%), accumulated dry matter (r = 0.66, CV = 15%), grain yield (r = 0.55, CV = 21%), and pod yield (r = 0.45, CV = 18%). Local sensitivity analysis with 23 parameters indicated that two parameters related to leaf development and a parameter related to yield formation were the most sensitive cultivar-specific parameters; thus, estimation of the parameters need to be done with care for new cultivars. The SSM provided an adequate level of peanut growth simulation and based both on its transparency and easiness-to-use can be used as a valid tool for simulating growth of peanut Virginia-type varieties.

Seismic response of base isolated nuclear power plants considering impact to moat walls

Seismic isolation can be an effective strategy to protect critical facilities including Nuclear Power Plants (NPPs) from the damaging effects of horizontal earthquake ground shaking. The increased flexibility at the base and resulting elongation of the natural vibration period of the structure leads to significant reductions in forces and acceleration transmitted to the structure above the isolation level at the expense of displacements concentrated in the isolation system. Displacement demands can be large at sites of moderate to high seismic hazard and can be accommodated by a horizontal clearance or moat at the isolation level, typically located in the basement of a structure. A surrounding moat wall can function as a stop to limit isolation system displacements and prevent bearing failure under beyond design basis shaking. However, impact of the isolated structure against the moat wall is of concern due to potential amplification in response of the superstructure. Design guidelines aim to prevent impact by specifying a required minimum clearance to stop (CS) with a low annual frequency of exceedance. A CS below the required value can be justified through analysis considering impact to the moat wall or stop. However, little guidance is available on how to model impact to the moat wall and resulting effects on the NPP superstructure. This study proposes a simplified model for impact simulation that captures the impact forces and the effects of impact on the response of seismically isolated NPPs. Variable clearance to the stop and a range of properties for the moat wall and isolation system are considered to identify parameters that influence the response. Results of these studies indicate that large NPP plants as considered here can have significant penetration into the moat wall, and thus not fully limit displacements in the isolation system, while having considerable increases in accelerations throughout the height of the NPP model.

From Reality to Simulation – Using the C&C2-Approach to Support the Modelling of a Dynamic System

Knowledge of a systems dynamic behavior is often necessary for successful product development. To gain this knowledge, simulation models can be used. In the process of building up these models, the real dynamic system is simplified. A challenge of simplification is the identification of relevant parameters of the technical system, so that the simplified simulation model can be used to gain necessary knowledge about the system behaviour. In this contribution it was investigated, how the C&C2-Approach can support the identification of relevant parameters for the simulation model. As method of examination a Single Case Study was used. In the case a simulation model of an overload clutch was developed by a design engineer who was already familiar with the C&C2-Approach. To gain qualitative findings a retrospective semi-structured interview was conducted with the design engineer. The result of this interview was that using the C&C2-Approach in the system analysis was evaluated as supportive by the design engineer in the process of simplification and documentation of the system. The simplification was supported through the structuring of the system using the key elements of the C&C2-Approach. The design engineer followed the flow of forces and focused on the embodiment that influences the torque transmission of the technical system. The results of the analysis with the C&C2-Approach were visualised and documented in a C& C²-Modell, which supported the collaborative working and discussing with other design engineers.

Simple mathematical model for the numerical simulation of formaldehyde and acetaldehyde formed in the exhaust of a combustion engine operating with ethanol as fuel

Simple mathematical model for the numerical simulation of formaldehyde and acetaldehyde formed in the exhaust of a combustion engine operating with ethanol as fuel

Laminated NbTi-on-Kapton Microstrip Cables for Flexible Sub-Kelvin RF Electronics

Large arrays of superconducting devices such as microwave kinetic inductance detectors require high density interconnects from higher temperatures with minimal heat load, low loss, and negligible crosstalk capable of carrying large and overlapping bandwidth signals. We report the fabrication of superconducting 53 wt% Nb-47 wt% Ti (Nb-47Ti) microstrip transmission lines laminated onto flexible polyimide substrates with lengths up to 40 cm and up to ten traces. The 50 Ω traces terminate in G3PO coaxial push-on connectors. We found transmission losses of 2.5 dB and a nearest-neighbor forward crosstalk of -25 dB at 8 GHz on a typical 5 trace, 1.8-cm-wide, 0.198-mm-thick, 22-cm-long flex cable at 30 mK. A simple two-port analytical model and subsequent Sonnet simulations indicate that this loss is mainly due to a complex impedance mismatch from wirebonds at the end connector without which the insertion loss would be <;2.7 dB/m. This is about six times worse than the transmission measured in Coax Company, Ltd.'s smallest (O 0.86 mm) Nb-47Ti coaxial cables, possibly from differences in the low temperature loss properties of polyimide laminates versus PTFE or from unaccounted resistive losses in the copper adapter coaxes of our tested device. Heat flow calculations from literature data show that the 0.198-mm-thick flex cables tested have roughly equivalent thermal conductance per trace below 4 K compared to the O 0.86 mm Nb-47Ti coaxial cables.

Discussions on simplified model for Simulation of induction bending

Discussions on simplified model for Simulation of induction bending

A Simplified Simulation Model of Ship Navigation for Safety and Collision Avoidance in Heavy Traffic Areas

Based on our previously developed ship collision avoidance steering system, this paper develops a more extensive collision avoidance decision-making system for non-uniformly moving ships. A real-time simulator based on the Six-Dimensional (6D) Manoeuvring Modelling Group (MMG) model is used to simulate the ship's motion. To validate the manoeuvring mathematical model, sea trial measurements of a container ship (C-3) have been selected. This study incorporates Nomoto's second-order model into a numerical model to calculate the turning characteristics of the ship. The manoeuvring indices of Nomoto's model are the knowledge base of the simplified ship simulation model. To verify the ship collision avoidance system with respect to different traffic factors, simple and complex collision avoidance cases have been designed in fast-time simulations with multi-ship encounter conditions. The simplified simulation model developed here can quickly determine the helm angle when the ship makes a collision avoidance manoeuvre, which is helpful for the safety of ship navigation in heavy traffic areas.

Simplified bead-chain model for direct fiber simulation in viscous flow

For efficient simulation of the motion of fibers during processing of fiber-reinforced thermoplastics, we propose a simplification of the bead-chain model (BCM), in which each fiber is modeled as a chain of spheres. The proposed simplified bead-chain model (SBCM) solves only one equation of translational motion, whereas the BCM requires three equations. The effects of bending and hydrodynamic torques, which are considered in the equation of rotational motion in the BCM, are expressed in the SBCM by adding terms to the equation of translational motion, although twisting motion is ignored. The validity of the SBCM is examined by comparing the results of both models when simulating the behavior of a single fiber and fiber suspensions in a simple shear flow. The SBCM provides results comparable to those of the BCM with lower computation time. This suggests that the SBCM could be an efficient alternative to the BCM.

Investigating local parity violation in heavy-ion collisions using Λ helicity

We propose the measurement of net $\Lambda$ and $\bar{\Lambda}$ helicity, correlated event-by-event with the magnitude and sign of charge separation along the event's magnetic field direction, as a probe to investigate the Chiral Magnetic Effect in Heavy-Ion Collisions. With a simple simulation model of heavy-ion events that includes effects of Local Parity Violation, we estimate the experimental correlation signal that could be expected at RHIC given the results of previous measurements that are sensitive to the CME.

Tire–rim interface pressure of a commercial vehicle wheel under radial loads: theory and experiment

The simulation of the radial fatigue test of a wheel has been a necessary tool to improve the design of the wheel and calculate its fatigue life. The simulation model, including the strong nonlinearity of the tire structure and material, may produce accurate results, but often leads to a divergence in calculation. Thus, a simplified simulation model in which the complicated tire model is replaced with a tire-wheel contact pressure model is used extensively in the industry. In this paper, a simplified tire–rim interface pressure model of a wheel under a radial load is established, and the pressure of the wheel under different radial loads is tested. The tire–rim contact behavior affected by the radial load is studied and analyzed according to the test result, and the tire–rim interface pressure extracted from the test result is used to evaluate the simplified pressure model and the traditional cosine function model. The results show that the proposed model may provide a more accurate prediction of the wheel radial fatigue life than the traditional cosine function model.

Observing propagating jet meanders in a numerical simulation of large-scale oceanic and atmospheric dynamics

Theoretical physicists investigate wavenumber-frequency spectra of various flow regimes using a simple numerical simulation model.

The Triple Spar Campaign: Implementation and Test of a Blade Pitch Controller on a Scaled Floating Wind Turbine Model

In this project by the University of Stuttgart, DTU Wind Energy and CENER, a real-time blade-pitch control system was implemented on a scaled model in a combined wind-and-wave tank. A simplified low-order simulation model including aerodynamics, hydrodynamics, mooring dynamics and structural dynamics was used to design the controller. Some effort has been made to investigate the influence of different gain scheduling methodologies of the collective blade-pitch controller on the dynamic behavior of the floating wind turbine. The issue relating to the negative aerodynamic damping is also investigated in order to find out whether the effects seen in simulation models can be equally reproduced by model tests. Additionally, wind and wave-induced responses with different gain scheduling methodologies and the difference to the tests without blade-pitch control are discussed. A solution for the hardware implementation of the real-time controller has been introduced. The developed controller is proven to function throughout the test campaign, which also proves the reliability of the simplified simulation model for controller design. It has been shown that with the low-Reynolds rotor it is possible to control the rotor speed at Froude-scaled frequencies by actuating the blade pitch angle.

A simple analytical infiltration model for short-duration rainfall

Many infiltration models have been proposed to simulate infiltration process. Different initial soil conditions and non-uniform initial water content can lead to infiltration simulation errors, especially for short-duration rainfall (SHR). Few infiltration models are specifically derived to eliminate the errors caused by the complex initial soil conditions. We present a simple analytical infiltration model for SHR infiltration simulation, i.e., Short-duration Infiltration Process model (SHIP model). The infiltration simulated by 5 models (i.e., SHIP (high) model, SHIP (middle) model, SHIP (low) model, Philip model and Parlange model) were compared based on numerical experiments and soil column experiments. In numerical experiments, SHIP (middle) and Parlange models had robust solutions for SHR infiltration simulation of 12 typical soils under different initial soil conditions. The absolute values of percent bias were less than 12% and the values of Nash and Sutcliffe efficiency were greater than 0.83. Additionally, in soil column experiments, infiltration rate fluctuated in a range because of non-uniform initial water content. SHIP (high) and SHIP (low) models can simulate an infiltration range, which successfully covered the fluctuation range of the observed infiltration rate. According to the robustness of solutions and the coverage of fluctuation range of infiltration rate, SHIP model can be integrated into hydrologic models to simulate SHR infiltration process and benefit the flood forecast.

Urban stormwater inundation simulation based on SWMM and diffusive overland-flow model.

With rapid urbanization, inundation-induced property losses have become more and more severe. Urban inundation modeling is an effective way to reduce these losses. This paper introduces a simplified urban stormwater inundation simulation model based on the United States Environmental Protection Agency Storm Water Management Model (SWMM) and a geographic information system (GIS)-based diffusive overland-flow model. SWMM is applied for computation of flows in storm sewer systems and flooding flows at junctions, while the GIS-based diffusive overland-flow model simulates surface runoff and inundation. One observed rainfall scenario on Haidian Island, Hainan Province, China was chosen to calibrate the model and the other two were used for validation. Comparisons of the model results with field-surveyed data and InfoWorks ICM (Integrated Catchment Modeling) modeled results indicated the inundation model in this paper can provide inundation extents and reasonable inundation depths even in a large study area.

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

Ecologists fiercely debate the role of soil conditions and fire regimes in controlling forest – savanna boundaries. A prominent component of this debate centres on the plausibility and existence of fire-mediated alternative stable state dynamics (FMASS), a model first proposed by the Tasmanian ecologist WD Jackson in 1968. The FMASS model asserts that increased or decreased landscape fire activity, often due to human intervention, can overwhelm physical environmental (e.g. topography and edaphic factors) controls of forest and savanna mosaics, thereby creating landscape dynamism. Many FMASS models include fire-vegetation-soil interactions (FVS), in which changes in fire frequency can change soil fertility and hence tree growth. This interaction, in turn, affects the capacity offorests to recover from disturbance and long unburnt savanna to convert to forest. We evaluate support for the FMASS-FVS model in the context of the dynamics of the Tasmanian forests that have recently been drawn into wider, global debates surrounding the co-occurrence of tree and treeless vegetation states. We develop a simple spatial simulation model to illuminate the difficulties in analysing landscape pattern to draw inferences about the existence of FMASS-FVS. Our review of the Tasmanian evidence shows that FMASS-FVS cannot unambiguously explain all tracts of sedgelands in Tasmanian wet forests, and hence Tasmania should not be used as an exemplar of these theories globally. Our simulations highlight that soil sampling that targets forest boundaries risks erroneously concluding that the distribution of forest and savanna boundaries is decoupled from edaphic factors. We describe a structured methodological pathway that can identify the role of FMASS-FVS in Tasmanian forest dynamics, and elsewhere in the world. This approach use cross-scale temporal and spatial analyses, and targeted experimental tests, to illuminate the interplay of fire, vegetation and edaphic factors in controlling tree establishment and growth and forest boundary dynamics.

A systematic approach for airflow velocity control design in road tunnels

This paper introduces a systematic approach to design and tune the airflow velocity control system for use during fire situations in road tunnels. The proposed approach is focused on road tunnels with a complex structure; long tunnels with connected ramps (entrances and exits), where the controller design can be challenging and time consuming. Such tunnels usually have many sections where a fire can be localized, and this makes the control task difficult. Our approach is based on a simplified one-dimensional simulation model of a tunnel, which includes all the important factors influencing the airflow dynamics of a tunnel. The proportional–integral (PI) controllers are tuned based on the Skogestad Internal Model Control (SIMC) method, which requires a simple model for the process dynamics. The case study is the airflow velocity control in the Blanka tunnel complex in Prague, Czech Republic, which is the largest city tunnel in Central Europe. The results of the paper show how to improve the control algorithm in real operation and how to use the proposed systematic approach for future tunnels.

Ferroelectric Phase Behaviors in Porous Electrodes.

The phase behavior of ions in porous electrodes is qualitatively different from that in the bulk because of the confinement effect and the interaction between the electrode surface and the electrolyte ions. We found that porous electrodes of which the pore size is close to the size of the electrolyte ions can show ferroelectric phase behaviors in some conditions by Monte Carlo simulations of simple models. The phase behavior of the porous electrodes dramatically changes as a function of the pore size of the porous electrode and that is compared to the phase behavior of typical ferroelectric materials, for which the phase behavior changes as a function of the temperature or the composition. The origin of the phase behavior is discussed in terms of the molecular interaction and the ionic structure inside the porous electrodes. We also found that the density of counterions and that of co-ions inside porous electrodes changes in a nonlinear fashion as a function of the applied voltage, which is in agreement with the experimental results.