Kind Of Simulation Research Articles

An Upper Bound for the Reachability Problem of Safe, Elementary Hornets

In this paper we study the complexity of the reachability problem HORNETS, an algebraic extension of object nets. Here we consider the restricted class of safe, elementary HORNETS. In previous work we established the lower bound, i.e. reachability requires at least exponential space. In another work we have shown we can simulate elementary HORNETS with elementary object nets EOS, where reachability is known to be PSpace-complete. Since this simulation leads to a double exponential increase in the size of the simulating EOS, we obtain that for HORNETS the reachability problem is solvable in double exponential space. In this contribution we show that this kind of simulation is rather bad, since we show that exponential space is sufficient. Together with the known lower bound this shows that the upper is tight.

Structural Studies of Fibril Formations of Tetrapeptides Using Replica Exchange Molecular Dynamics Simulations

Amyloid fibrils are peptide or protein aggregates, which are found in about 20 diseases such as Alzheimer's disease, transmissible spongiform encephalopathies, Parkinson's disease, and type II diabetes mellitus [1]. However, the reasons for amyloid association disease are unclear. Therefore, in order to examine the mechanism of fibril formations, we have performed molecular dynamics simulations using some peptides and fragments of amyloid beta protein [2]. In this study, we used short model peptides, which have KFFE amino acid sequence, and form fibrils in experiments [3]. Especially, we focused on the concentration dependency of the peptide aggregation. The some kinds of simulations were performed with different concentrations for each system by using replica exchange dynamics simulations (REMD) [4]. From these simulations, we examined the dependency between beta-structure tendency and the concentration of the peptides.[1] Rochet, J. C., and Lansbury, P. T., Jr. Curr. Opin. Struct. Biol. vol. 10, 60-68 (2000).[2] Nishikawa, N., Sakae, Y., Okamoto, Y., Proceedings of Computational Science Workshop 2014, 011020, 10.7566 (2014).[3] Tjernberg, L., Hosia, W., Bark, N., Thyberg, J., Johansson, J., J. Biol. Chem. vol. 277, pp.43243-43246 (2002).[4] Sugita, Y., Okamoto, Y., Chem. Phys. Lett. vol. 314, pp.141-151 (1999).

Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations

Abstract. Large eddy simulations (LESs) are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, we use the cell perturbation method based on finite amplitude potential temperature perturbations. In this work, this method is for the first time tested and validated for moist boundary layer simulations with open lateral boundary conditions. Observational data obtained from the SALTRACE field campaign is used for both model initialization and a comparison with Doppler wind and Raman lidar data. Several numerical sensitivity tests are carried out to demonstrate the problems related to “gray zone modeling” when using coarser spatial grid spacings beyond the inertial subrange of three-dimensional turbulence or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties in the downwind area west of Barbados are markedly affected in these kinds of simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and location. Saharan dust layers that reach Barbados via long-range transport over the North Atlantic are included as passive tracers in the model. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom at z ≈ 1800 m become apparent. The exact position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability (especially inversion strength) and wind shear. Comparisons of LES model output with wind lidar data show similarities in the downwind vertical wind structure. Additionally, the model results accurately reproduce the development of the daytime convective boundary layer measured by the Raman lidar.

On the Effect of an Aggressive Inlet Swirl Profile on the Aero-thermal Performance of a Cooled Vane

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis has been performed (with uniform inlet flow) to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experiment data. The effects of a realistic inlet swirl on the aero-thermal performance of the cooling system are then investigated by means of comparison between two different kinds of simulations. The first one using a uniform inlet flow while the second one with aggressive swirl derived from the EU-funded project TATEF2. Clocking effects are also accounted for. The effect of the swirling flow in determining the coolant transport are investigated, evidencing the key role that these phenomena have in determining the effectiveness of the cooling.

Using 2D and 3D Computer Games to Detect Colorblindness – a Comparative Study

Abstract Computer games have accompanied the development of computer technologies since the very beginning. Despite their basic, purely entertainment-targeted appliance, games can also be used for many other purposes. Medical applications are especially interesting, as games (especially different kinds of simulations) are widely used for training personnel, e.g. to perform certain procedures or in learning to use equipment. This allows the trainees to gain knowledge and proper habits, as well as test themselves in different situations without any risk. Computer games can also be used as a diagnostic tool, although this topic is still insufficiently researched. This paper discusses the possibility of using serious games for diagnosing color vision disorders, focusing especially on two problems: differences in diagnosing colorblindness using 2D and 3D environments, and the influence of individual features, such as reflex or agility, on the diagnostic process.

CFD ANALYSIS OF THE SPACER GRIDS AND MIXING VANES EFFECT ON THE FLOW IN THE CHOSEN PART OF THE TVSA-T FUEL ASSEMBLY

<p>CFD is a promising and widely spread tool for a flow simulation in nuclear reactor fuel assemblies. One of the limiting factors is the complicated geometry of a spacer grid. It leads to the computational mesh with high number of cells and with possibility of decreasing quality. Therefore an approach to simulate the flow as precisely as possible and simultaneously in a reasonable computational expense has to be chosen. The goal of the following CFD analysis is to obtain the detailed velocity field in a precise geometry of <br /> a chosen part of the TVSA-T fuel assembly. This kind of simulation provides data for comparison that can be applied in many situations, for instance, for comparison with simulations when a porous media boundary condition is applied as a replacement of the spacer grid.</p><p>TVSA-T fuel assembly is equipped with combined spacer grids. Combined spacer grid has two functions - support of the fuel pins as a part of assembly skeleton and mixing vanes which ensures coolant mixing. The support part is geometrically very complicated and it is impossible to prepare a good quality computational mesh there. It is also difficult to create a mesh in the support part and the mixing part joint area because of inaccurate connection between these two parts.</p><p>A representative part of the TVSA-T fuel assembly with a combined spacer grid segment was chosen to perform the CFD simulation. Some inevitable geometry simplifications of the spacer grid geometry were performed. These simplifications were as insignificant as possible to preserve the flow character and to make it possible to prepare <br /> a quality mesh at the same time.</p><p>Steady state CFD simulation was performed with k-ε realizable turbulence model. Heat transfer was not simulated and only velocity field was investigated. Detailed flow characterization which was obtained from this calculation shown, that mixing vanes already affect the flow in the support part of the grid thanks to suction effect. Vortex structures disappear approximately 50 mm behind the mixing vanes but the basic spiral character of the flow is preserved in the whole area between two following spacer grids.</p>

Simulation and Spacecraft Design: Engineering Mars Landings.

A key issue in history of technology that has received little attention is the use of simulation in engineering design. This article explores the use of both mechanical and numerical simulation in the design of the Mars atmospheric entry phases of the Viking and Mars Pathfinder missions to argue that engineers used both kinds of simulation to develop knowledge of their designs' likely behavior in the poorly known environment of Mars. Each kind of simulation could be used as a warrant of the other's fidelity, in an iterative process of knowledge construction.

Study on the Spring-Back Effect with Stress Distribution According to Forming Sheet Width in the Roll Forming Process

This study, based on finite element analysis, analyzed the spring back phenomenon and stress distribution of forming sheets (HTS) in the roll forming process. By comparison of the stress distribution, this study analyzed two kinds of simulation. The first simulation performed simple bending simulation before roll forming simulation. With reference to the first simulation results, the second simulation analyzed the relationship between the stress distribution and the phenomenon of spring back. We also studied the stress distribution effect for spring back in the forming sheet.

Simulation of ultrasound wave propagation in heterogeneous materials

The simulation of ultrasound waves propagating through heterogeneous materials is useful to a range of applications, including Nondestructive Evaluation (NDE) and materials characterization. In NDE, the challenge is to detect defects within the volume of a component against a background of noise of scattering from the inhomogeneities. In materials characterization, the challenge is to measure properties such as stiffness, texture, and spatial distributions of the inhomogeneities. Until recently, simulation of wave propagation through realistic detailed volumetric representations of heterogeneous materials was infeasible because of the huge computational requirements. However, it has recently become possible to do these kinds of simulations. This talk will show Finite Element model simulations of wave propagation in polycrystalline metals that are representative of the high performance alloys used in electricity power plant components. Validations by examining wave speed, attenuation, and backscatter will be discussed, and example deployments of the models will be presented.

Study of the influence of computational parameters on the formation of a giant gaseous planet

Today, computational simulatios are the best method to describe the formation of our Solar System, however this kind of simulations contain numerical errors caused by boundary conditions and choises of the grid, for instance. In this paper we will present results from several hidrodynamical simulations of the formation of a planet like Jupiter able to migrate using different computational parameters. We will compare the density profile, the semimajor axis and the eccentricity of the planet for those different parameters and measure the effect of them. We will not extend our results for planets with initial eccentric orbits in this paper.

Urban inundation simulation considering road network and building configurations

AbstractThe main difference between rural and urban area inundation is the existence of an impermeable layer and the complexity of the road and building configuration. Therefore, although surface overland flow can be appropriately simulated by the two‐dimensional diffusive model in a rural area, there also is a need for a more accurate and elaborate simulation model. Dual drainage concept has been popular to simulate urban drainage system. Although the concept has immense advantages, through which overland flow and pipe flow can be simulated simultaneously, many researchers set manholes as discharge exchange spots between ground surface and sewerage system, which causes lack of reality. Therefore, in this study, we developed a new urban inundation model that can reflect real field situation. Also, two kinds of simulations are carried out with homogeneous meshes and non‐homogeneous ones using manholes and storm drains as discharge exchange spots, respectively, and those results are compared to estimate the effect of road networks and building groups according to different discharge exchange spots. Two‐dimensional run‐off flow model and one‐dimensional slot‐model are used to simulate ground surface run‐off flow and sewer pipe flow. To connect both models, we used a newly suggested bi‐directional model and its coefficients. The simulated results showed that more reasonable results are obtained in the nonhomogeneous case; the results further reveal the importance of using storm drains as exchange spots in the model.

Reality-based court interpreting didactic material using new technologies

Training for future court interpreters has traditionally been based on role-play exercises, recreations of actual trials or audios based on prototypical communicative situations. In the case of interpreting in court these kinds of simulations are not enough to train future court interpreters, since they do not fully reflect the great complexity of real communication in court. This article is intended to present a new reality-based audiovisual training material specifically devoted to court interpreters training in Spain. The material was inspired by the positive results of the conference interpreting teaching materials developed using real videos at the University of Granada. One of the most interesting aspects of the material presented here is its exclusivity, as it is, to date, the only didactic material for court interpreting training that achieves such a high degree of authenticity, since it works on the basis of real criminal trials. The material takes into account well-known translation subcompetences and it specifically addresses students who have previously received training in conference interpreting.

A scintillation light radial distribution model for monolithic crystal gamma cameras

Gamma imaging systems are often based on monolithic scintillators coupled to a light detector through a certain number of light guides, like glass or grease. In order to predict and optimize gamma camera performance in terms of bias and spatial resolution, accurate Monte Carlo simulations are usually carried out. These kind of simulations require high computational time so only a small number of arrangements are investigated. In this work we propose a mathematical model of scintillation light propagation starting from the gamma interaction point to the detector surface. This model gives the expression for the radial photon density distribution with a computational time 4 order of magnitude shorter than a Monte Carlo simulation. The model has been validated with standard Monte Carlo simulations of five system configurations, showing a percentage error on the quantitative evaluation of photon number lower than 2%.

A Model for the Transport of Sea-Spray Aerosols in the Coastal Zone

We study the dynamics of sea-spray particles in the coastal region of La Reunion Island on the basis of numerical simulations using the transport aerosol model MACMod (Marine Aerosol Concentration Model) and a survey of the aerosol size distributions measured at four locations at two different heights in the north-west part of the island. This allows evaluation of the performance of our model in case of pure marine air masses with implementation of accurate boundary conditions. First of all, an estimate of the aerosol concentration at 10-m height at the upwind boundary of the calculation domain is obtained using a revisited version of the MEDEX (Mediterranean Extinction) model. Estimates of the vertical profile of aerosol concentrations are then provided using aerosol data obtained at two different heights at the upwind boundary of the calculation domain. A parametrization of the vertical profiles of aerosol concentrations for maritime environment is proposed. The results are then compared to the vertical profiles of 0.532 $$\upmu $$ m aerosol particle extinction coefficient obtained from lidar data provided by the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) and also to the data provided by the Aerosol Robotic Network (AERONET). This allows validation of the complete vertical profiles in the mixed layer and shows the validity of satellite data for determination of the vertical profiles. Two kinds of simulation were made: one without a particle advection flux at the upwind boundary of the numerical domain, whereas the second simulation was made with a particle advection flux. In the first case, the influence of the distance to the shoreline on the local sea-spray dynamics is investigated. In the second set of simulation, the particles issued from the local production in the surf zone near the shoreline are mixed with aerosols advected from the remote ocean. A good agreement between the model calculations using our boundary conditions and the data was found. The present results then attest the ability of this kind of model, as a first approach to predicting the local transport of sea-spray particles in a pure marine environment.

Equilibrium and non-equilibrium charge-state distributions of 2.0 MeV/u carbon ions passing through carbon foils

Both equilibrium and non-equilibrium charge-state distributions were studied experimentally for 2.0MeV/u carbon ions after passing through carbon foils. Measured charge-state distribution established the equilibrium at a target thickness of 10μg/cm2 and this remained unchanged until a maximum target thickness of 98μg/cm2. The equilibrium charge-state distribution, the equilibrium mean charge-state, and the width and skewness of the equilibrium distribution were compared with predictions using existing semi-empirical formulae as well as simulation results, including the ETACHA code. It was found that charge-state distributions, mean charge states, and distribution widths for C2+, C3+, and C4+ incident ions merged into quasi-equilibrium values at a target thickness of 5.7μg/cm2 in the pre-equilibrium region and evolved simultaneously to the ‘real equilibrium’ values for all of the initial charge states, including C5+ and C6+ ions, as previously demonstrated for sulfur projectile ions at the same velocity (Imai et al., 2009). Two kinds of simulation, ETACHA and solution of rate equations taking only single electron transfers into account, were used, and both of them reproduced the measured charge evolution qualitatively. The quasi-equilibrium behavior could be reproduced with the ETACHA code, but not with solution of elementary rate equations.

Numerical Simulation of Oblique Towing Tests and Rotating Arm Tests for a Submarine Model in Same Grid Topology

The numerical simulation of oblique towing tests (OTT) and rotating arm tests (RAT) for a submarine model was undertaken with the same grid topology. As for the OTT simulation, to improve the efficiency and accuracy of the computation, the drift sweep procedure was adopted. In contrast with the steady drift case, rotating motion for a submarine is more complex. The rotating reference frame was adopted to deal with the rotation problem. The Coriolis force and centrifugal force due to the computation in a body-fixed rotating coordinate system were treated explicitly and added to the momentum equations as source terms. The user-defined boundary conditions were coded to give the correct magnitude and direction of entrance velocity. Lastly, the computed forces and moments as a function of drift angle during the two kinds of simulations were compared with experimental results, as well as literature values. They always show the correct trend. The flow field and streamline patterns in rotating motion were depicted. It indicates that the method used in the paper is reliable and the same grid topology can be used for the simulation of two simplified maneuvers.

High performance simulation technology in the Internet of Things

The Internet of Things based on sensors is bound to trigger an epoch–making revolution in military affairs. However, the multitudinous sensors increase the processing time of a computer. This makes battlefield simulation get into great trouble. In addition, the outcome of a war is affected by many factors and an excellent battlefield simulation should consider these factors comprehensively. The supercomputer with the capabilities of ultra computation and communication should be applied into this kind of simulation. After introducing the hardware architecture of a high performance simulation supercomputer, this paper presents several techniques in our battlefield simulation software such as its monitoring policy, design principles and scheduling algorithm. These techniques are helpful to monitor the status of the supercomputer with numerous multi–core CPUs and enormous samples of a battlefield program can be easily deployed and executed in batch. The evaluation conclusion of different samples for the battlefield situation can provide powerful support for the commander.

Numerical performance analysis of oscillating water column device using sea waves

This study investigates the efficiency of an oscillating water column (OWC) wave energy convertor using numerical simulation. For the OWC device, it was assumed that inertial water free-surface of the OWC acts as a floating rigid body. Hence, the radiation potential term is considered in the model. Analysis is performed in frequency domain based on linear wave theory and potential flow. The model was validated against experimental data based on output pressure. This comparison revealed that the model is accurate enough for this kind of simulation. Further investigations showed that outgoing air pressure increases with increase in the wave period. Furthermore, the output power of device reduces with increasing the submerged depth.

Research of Power Plant Boiler Control System Based on Compensatory Fuzzy Neural Network

Considering thermal power plant boiler’s nonlinear, large delay and time-varying, the paper proposes a compensatory fuzzy neural network control based on fuzzy control and neural network control. The compensatory fuzzy neural network is better than the PID controller and general fuzzy network controller in properties by using fuzzy inference and compensatory arithmetic. The paper makes a preliminary simulation using simulation tools of Matlab. And, the superiority of the compensatory fuzzy neural network control is proved by comparing the two kinds of simulation.

Local Global Method for the Prediction of Surface Residual Stresses in 3D Turning

Numerical simulation of turning is still one of the best solutions to understand and improve such a process. Since many years, researchers have tried to use several numerical approaches to go round the difficulties and to set up reliable models (Lagrangian, ALE,…). Currently no perfect complete solution is available and it is time to introduce dedicated models prone to simulate partially the phenomena in order to reach specific conditions linked with real industrial problematics. This paper will present a 3D local global method set up to predict surface residual stresses in finish turning. This approach uses two kinds of simulations. A first one that allows reaching thermo mechanical steady state around the cutting edge and the chip area. A second one which sequences the application of the extracted thermo mechanical fields onto the real workpiece surface. The obtained results concerning the residual stresses fields will then be compared with the ones recorded experimentally.