scholarly journals FRACS: modelling of the dust disc of the B[e] CPD-57° 2874 from VLTI/MIDI data

2010 ◽  
Vol 6 (S272) ◽  
pp. 382-383
Author(s):  
Philippe Bendjoya ◽  
Armando Domiciano de Souza ◽  
Gilles Niccolini
Keyword(s):  
Computing Time ◽  
Mid Infrared ◽  
Fitting Procedure ◽  
Dust Temperature ◽  
Tracing Algorithm ◽  
Short Computing Time ◽  
Time Required ◽  
Best Fit ◽  
Physical Quantities ◽  
Automatic Fitting

AbstractThe physical interpretation of spectro-interferometric data is strongly model dependent. On one hand, models involving elaborate radiative transfer solvers are in general too time consuming to perform an automatic fitting procedure and derive astrophysical quantities and their related errors. On the other hand, using simple geometrical models does not give sufficient insights into the physics of the object. We developed a numerical tool optimised for mid-infrared (mid-IR) interferometry, the Fast Ray-tracing Algorithm for Circumstellar Structures (FRACS). Thanks to the short computing time required by FRACS, best-fit parameters and uncertainties for several physical quantities were obtained, such as inner dust radius, relative flux contribution of the central source and of the dusty CSE, dust temperature profile, disc inclination.

scholarly journals Closed-Form Expressions for Numerical Evaluation of Self-Impedance Terms Involved on Wire Antenna Analysis by the Method of Moments

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1316
Author(s):  
Carlos-Ivan Paez-Rueda ◽  
Arturo Fajardo ◽  
Manuel Pérez ◽  
Gabriel Perilla
Keyword(s):  
Numerical Integration ◽  
Method Of Moments ◽  
Computing Time ◽  
Basis Functions ◽  
Wire Antenna ◽  
Complex Geometries ◽  
Point Matching ◽  
Piecewise Constant ◽  
Matching Procedure ◽  
Time Required

This paper proposes new closed expressions of self-impedance using the Method of Moments with the Point Matching Procedure and piecewise constant and linear basis functions in different configurations, which allow saving computing time for the solution of wire antennas with complex geometries. The new expressions have complexity O(1) with well-defined theoretical bound errors. They were compared with an adaptive numerical integration. We obtain an accuracy between 7 and 16 digits depending on the chosen basis function and segmentation used. Besides, the computing time involved in the calculation of the self-impedance terms was evaluated and compared with the time required by the adaptative quadrature integration solution of the same problem. Expressions have a run-time bounded between 50 and 200 times faster than an adaptive numerical integration assuming full computation of all constant of the expressions.

Parameter Based Combustion Model for Large Prechamber Gas Engines

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Jianguo Zhu ◽  
Andreas Wimmer ◽  
Eduard Schneßl ◽  
Hubert Winter ◽  
Franz Chmela
Keyword(s):  
Computing Time ◽  
Combustion Process ◽  
Combustion Model ◽  
Operating Parameters ◽  
Transfer Model ◽  
Boost Pressure ◽  
Considerable Difficulty ◽  
Single Cylinder ◽  
Simulation And Optimization ◽  
Short Computing Time

Challenging requirements for modern large engines regarding power output, fuel consumption, and emissions can only be achieved with carefully adapted combustion systems. With the improvement of simulation methods simulation work is playing a more and more important role for the engine development. Due to their simplicity and short computing time, one-dimensional and zero-dimensional calculation methods are widely applied for the engine cycle simulation and optimization. While the gas dynamic processes in the intake and exhaust systems can already be simulated with sufficient precision, it still represents a considerable difficulty to predict the combustion process exactly. In this contribution, an empirical combustion model for large prechamber gas engines is presented, which was evolved based on measurements on a single cylinder research engine using the design of experiment method. The combustion process in prechamber gas engines is investigated and reproduced successfully by means of a double-vibe function. The mathematical relationship between the engine operating parameters and the parameters of the double-vibe function was determined as a transfer model on the base of comprehensive measurements. The effects of engine operating parameters, e.g., boost pressure, charge temperature, ignition timing, and air/fuel ratio on the combustion process are taken into account in the transfer model. After adding modification functions, the model can be applied to gas engines operated with various gas fuels taking into account the actual air humidity. Comprehensive verifications were conducted on a single-cylinder engine as well as on full-scale engines. With the combination of the combustion model and a gas exchange simulation model the engine performance has been predicted satisfactorily. Due to the simple phenomenological structure of the model, a user-friendly model application and a short computing time is achieved.

scholarly journals Brief communication: Vehicle routing problem and UAV application in the post-earthquake scenario

2017 ◽  
Author(s):  
Marco Cannioto ◽  
Antonino D'Alessandro ◽  
Giosuè Lo Bosco ◽  
Salvatore Scudero ◽  
Giovanni Vitale
Keyword(s):  
Vehicle Routing ◽  
Vehicle Routing Problem ◽  
Seismic Event ◽  
Computing Time ◽  
Research Problem ◽  
Routing Problem ◽  
Earthquake Scenario ◽  
Short Computing Time ◽  
The Cost ◽  
The Town

Abstract. In this paper we simulate a Unmanned Aerial Vehicle's (UAV) recognition after a possible case of diffuse damage after a seismic event in the town of Acireale (Sicily, Italy). Given a set of sites (84 relevant buildings) and the range of the UAV, we are able to find the number of vehicles to employ and the shortest survey path. The problem of finding the shortest survey path is an operational research problem called Vehicle Routing Problem (VRP) whose solution is known to be computationally time-consuming. We used the Simulated Annealing (SA) heuristic that is able to provide stable solutions in relatively short computing time. We also examined the distribution of the cost of the solutions varying the depot on a regular grid in order to assess the best area where to execute the survey.

SnBversion 2.2: an example of crystallographic multiprocessing

2002 ◽  
Vol 35 (3) ◽  
pp. 374-376 ◽  
Author(s):  
Jason Rappleye ◽  
Martins Innus ◽  
Charles M. Weeks ◽  
Russ Miller
Keyword(s):  
Shared Memory ◽  
Distributed Memory ◽  
Computing Time ◽  
Direct Methods ◽  
Fixed Number ◽  
Linear Speedup ◽  
Beowulf Clusters ◽  
Shared Memory Multiprocessor ◽  
Computing Platforms ◽  
Time Required

The computer programSnBimplements a direct-methods algorithm, known asShake-and-Bake, which optimizes trial structures consisting of randomly positioned atoms. Although largeShake-and-Bakeapplications require significant amounts of computing time, the algorithm can be easily implemented in parallel in order to decrease the real time required to achieve a solution. By using a master–worker model,SnBversion 2.2 is amenable to all of the prevalent modern parallel-computing platforms, including (i) shared-memory multiprocessor machines, such as the SGI Origin2000, (ii) distributed-memory multiprocessor machines, such as the IBM SP, and (iii) collections of workstations, including Beowulf clusters. A linear speedup in the processing of a fixed number of trial structures can be obtained on each of these platforms.

Preprocessing of Coefficients for Reusable Continuous Wavelet Transform

2014 ◽  
Vol 1040 ◽  
pp. 975-979 ◽  
Author(s):  
Alexander A. Khamukhin ◽  
Alexey A. Khamukhin
Keyword(s):  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Computing Time ◽  
Continuous Wavelet ◽  
Wavelet Coefficients ◽  
Nonstationary Signal ◽  
Online Detection ◽  
Second Stage ◽  
Time Required ◽  
Two Stages

The division into two stages of the Continuous Wavelet Transform (CWT) computing is proposed. This is expedient in circumstances when CWT is repeated many times, e.g., for online detection of nonstationary signal singularities. It is shown that the preprocessing of wavelet coefficients in the first stage can significantly reduce computing time required in the second stage. The comparative estimation of the runtime reduction in the second stage of CWT calculation is deduced.

scholarly journals Fast Infrared Radiative Transfer Calculations Using Graphics Processing Units: JURASSIC-GPU v2.0

2021 ◽  
Author(s):  
Paul F. Baumeister ◽  
Lars Hoffmann
Keyword(s):  
Radiative Transfer ◽  
Data Processing ◽  
Graphics Processing Units ◽  
High Performance ◽  
State Of The Art ◽  
Computing Time ◽  
Global Scale ◽  
Computing Systems ◽  
Mid Infrared ◽  
Infrared Spectral

Abstract. Remote sensing observations in the mid-infrared spectral region (4–15 μm) play a key role in monitoring the composition of the Earth's atmosphere. Mid-infrared spectral measurements from satellite, aircraft, balloon and ground-based instruments provide information on pressure and temperature, trace gases as well as aerosols and clouds. As state-of-the-art instruments deliver a vast amount of data on a global scale, their analysis, however, may require advanced methods and high-performance computing capacities for data processing. A large amount of computing time is usually spent on evaluating the radiative transfer equation. Line-by-line calculations of infrared radiative transfer are considered to be most accurate, but they are also most time-consuming. Here, we discuss the emissivity growth approximation (EGA), which can accelerate infrared radiative transfer calculations by several orders of magnitude compared with line-by-line calculations. As future satellite missions will likely depend on Exascale computing systems to process their observational data in due time, we think that the utilization of graphical processing units (GPUs) for the radiative transfer calculations and satellite retrievals is a logical next step in further accelerating and improving the efficiency of data processing. Focusing on the EGA method, we first discuss the implementation of infrared radiative transfer calculations on GPU-based computing systems in detail. Second, we discuss distinct features of our implementation of the EGA method, in particular regarding the memory needs, performance, and scalability on state-of-the-art GPU systems. As we found our implementation to perform about an order of magnitude more energy-efficient on GPU-accelerated architectures compared to CPU, we conclude that our approach provides various future opportunities for this high-throughput problem.

Parameter Based Combustion Model for Large Pre-Chamber Gas Engines

2009 ◽  
Author(s):  
Jianguo Zhu ◽  
Andreas Wimmer ◽  
Eduard Schneßl ◽  
Hubert Winter ◽  
Franz Chmela
Keyword(s):  
Computing Time ◽  
Combustion Process ◽  
Combustion Model ◽  
Operating Parameters ◽  
Transfer Model ◽  
Boost Pressure ◽  
Single Cylinder ◽  
Simulation And Optimization ◽  
Short Computing Time ◽  
Chamber Gas

Challenging requirements for modern large engines regarding power output, fuel consumption and emissions can only be achieved with carefully adapted combustion systems. With the improvement of simulation methods simulation work is playing a more and more important role for the engine development. Due to their simplicity and short computing time, one-dimensional and zero-dimensional calculation methods are widely applied for the engine cycle simulation and optimization. While the gas dynamic processes in the intake and exhaust system can already be simulated with sufficient precision, it still represents a considerable difficulty to predict the combustion process exactly. In this contribution, an empirical combustion model for large pre-chamber gas engines is presented, which was evolved based on measurements on a single cylinder research engine using the DOE (Design of Experiments) method. The combustion process in pre-chamber gas engines is investigated and reproduced successfully by means of a Double-Vibe function. The mathematical relationship between the engine operating parameters and the parameters of the Double-Vibe function was determined as a transfer model on the base of comprehensive measurements. The effects of engine operating parameters e.g. boost pressure, charge temperature, ignition timing, air/fuel ratio on the combustion process are taken into account in the transfer model. After adding modification functions, the model can be applied to gas engines operated with various gas fuels taking into account the actual air humidity. Comprehensive verifications were conducted on a single cylinder engine as well as on full scale engines. With the combination of the combustion model and a gas exchange simulation model the engine performance has been predicted satisfactorily. Due to the simple phenomenological structure of the model, a user-friendly model application and a short computing time is achieved.

Proposal of Novel Icing Simulation Using a Hybrid Grid- and Particle-Based Method

2020 ◽  
Vol 36 (5) ◽  
pp. 699-706
Author(s):  
D. Toba ◽  
K. Fukudome ◽  
H. Mamori ◽  
N. Fukushima ◽  
M. Yamamoto
Keyword(s):  
Surface Roughness ◽  
Numerical Simulations ◽  
Computing Time ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Air Voids ◽  
Naca0012 Airfoil ◽  
Hybrid Grid ◽  
Short Computing Time ◽  
Grid Based

ABSTRACTIcing on aircraft can drastically reduce aerodynamic performance and lead to serious accidents. Therefore, prediction of the accreted ice shape and area and its effects on aerodynamic performance is crucial during the design phase of an aircraft. However, numerical simulations based on conventional grid-based methods such as the finite volume method cannot accurately reproduce the complex ice shapes, which involve horn growth, feather growth, air voids, and severe surface roughness. In the present study, instead of the grid-based method, a hybrid grid- and particle-based method was newly proposed and applied to the icing problem on a NACA0012 airfoil. The explicit moving particle semi-implicit method was employed as the particle-based method due to its short computing time. The numerical simulations effectively reproduced feather-shaped ice, air voids, and surface roughness. Finally, by computing the flow around the iced airfoil, it was confirmed that flow separation around the leading edge occurred due to the ice layer, which resulted in a thicker boundary layer and wake and an increase in the drag coefficient of approximately 70% after a residence time of only 60 seconds.

Development of Fatigue Design Curves for Pressure Vessel Alloys Using a Modified Langer Equation

1979 ◽  
Vol 101 (4) ◽  
pp. 292-297 ◽  
Author(s):  
D. R. Diercks
Keyword(s):  
Pressure Vessel ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Austenitic Stainless Steels ◽  
Cyclic Stress ◽  
Allowable Stress ◽  
Fitting Procedure ◽  
Fatigue Design ◽  
Alloy 800 ◽  
Best Fit

The Jaske and O’Donnell [1] curve-fitting procedure for analyzing fatigue data generated between room temperature and 427° C (800° F) for several pressure vessel alloys is reexamined in the present paper. Substantial improvements over their best-fit curves to the data are found to result from two proposed modifications to their procedure, namely 1) the use of a variable exponent in the Langer equation, and 2) minimization of the sum of the squares of the errors in the logarithms of the cyclic-stress amplitudes rather than in the stress amplitudes directly. Likewise, important differences are observed for the resultant allowable stress-amplitude values for design purposes. In particular, the present analysis permits higher allowable stress amplitudes in the critical low-cycle fatigue-life region for the austenitic stainless steels, alloy 800, and alloy 600. Two best-fit curves and the associated sets of allowable stress amplitudes, corresponding to the inclusion or deletion of load-controlled data, are obtained for alloy 718.

Modification and Numerical Method for the Jiles-Atherton Hysteresis Model

2017 ◽  
Vol 21 (3) ◽  
pp. 763-781 ◽  
Author(s):  
Guangming Xue ◽  
Peilin Zhang ◽  
Zhongbo He ◽  
Dongwei Li ◽  
Zhaoshu Yang ◽  
...  
Keyword(s):  
Numerical Method ◽  
Computing Time ◽  
Step Size ◽  
Mathematical Properties ◽  
Runge Kutta Method ◽  
Solution Methods ◽  
Uniform Solution ◽  
Computational Errors ◽  
Short Computing Time ◽  
Anhysteretic Magnetization

AbstractThe Jiles-Atherton (J-A) model is a commonly used physics-based model in describing the hysteresis characteristics of ferromagnetic materials. However, citations and interpretation of this model in literature have been non-uniform. Solution methods for solving numerically this model has not been studied adequately. In this paper, through analyzing the mathematical properties of equations and the physical mechanism of energy conservation, we point out some unreasonable descriptions of this model and develop a relatively more accurate, modified J-A model together with its numerical solution method. Our method employs a fixed point method to compute anhysteretic magnetization. We obtain the susceptibility value of the anhysteretic magnetization analytically and apply the 4th order Runge-Kutta method to the solution of total magnetization. Computational errors are estimated and then precisions of the solving method in describing various materials are verified. At last, through analyzing the effects of the accelerating method, iterative error and step size on the computational errors, we optimize the numerical method to achieve the effects of high precision and short computing time. From analysis, we determine the range of best values of some key parameters for fast and accurate computation.

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