369 research outputs found
FDTD/K-DWM simulation of 3D room acoustics on general purpose graphics hardware using compute unified device architecture (CUDA)
The growing demand for reliable prediction of sound fields in rooms have resulted in adaptation of various approaches for physical modeling, including the Finite Difference Time Domain (FDTD) and the Digital Waveguide Mesh (DWM). Whilst considered versatile and attractive methods, they suffer from dispersion errors that increase with frequency and vary with direction of propagation, thus imposing a high frequency calculation limit. Attempts have been made to reduce such errors by considering different mesh topologies, by spatial interpolation, or by simply oversampling the grid. As the latter approach is computationally expensive, its application to three-dimensional problems has often been avoided. In this paper, we propose an implementation of the FDTD on general purpose graphics hardware, allowing for high sampling rates whilst maintaining reasonable calculation times. Dispersion errors are consequently reduced and the high frequency limit is increased. A range of graphics processors are evaluated and compared with traditional CPUs in terms of accuracy, calculation time and memory requirements
Efficient excitation of waveguides in Crank-Nicolson FDTD
In this paper, we present a procedure to calculate the discrete modes propagated with Crank-Nicolson FDTD in metallic waveguides. This procedure enables the correct excitation of this kind of waveguides at any resolution. The problem is reduced to solving an eigenvalue equation, which is performed, both in a closed form, for the usual rectangular waveguide, and numerically in the most general case, validated here with a ridged rectangular waveguide.The work described in this paper and the research leading to these
results has received funding from the European Community's Seventh
Framework Programme FP7/2007-2013, under grant agreement
no 205294 (HIRF SE project), and from the Spanish National
Projects TEC2010-20841-C04-04, TEC2007-66698-C04-02, CSD2008-
00068, DEX-530000-2008-105, and the Junta de Andalucia Projects
TIC1541 and P09-TIC-5327
New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs
This work presents the development and systematic investigation of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyrotron traveling wave tubes (helical gyro-TWT). The frequency of 263 GHz is an established figure for continuous wave (CW) DNP-NMR application and, therefore, the investigated source will allow the development of novel spectroscopy methods such as time-domain DNP-NMR for which powerful sub-THz pulses with highest coherency are required.
For the first time, it is shown that the operation of the passive mode-locked helical gyro-TWTs in the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. To enable the operation in the hard excitation regime, a new extended passive mode-locked oscillator is proposed. The extended passive mode-locked oscillator will furthermore enable the generation of specific pulse sequences in addition to the generation of pulses with constant repetition frequency. This could be of particular interest for some time-domain DNP-NMR methods where well-defined pulse sequences are required
Numerical enhancements and parallel GPU implementation of the TRACEO3D model
Underwater acoustic models provide a fundamental and e cient tool to parametrically
investigate hypothesis and physical phenomena through varied environmental conditions
of sound propagation underwater. In this sense, requirements for model predictions in
a three-dimensional ocean waveguide are expected to become more relevant, and thus
expected to become more accurate as the amount of available environmental information
(water temperature, bottom properties, etc.) grows. However, despite the increasing
performance of modern processors, models that take into account 3D propagation still
have a high computational cost which often hampers the usage of such models. Thus,
the work presented in this thesis investigates a solution to enhance the numerical and
computational performance of the TRACEO3D Gaussian beam model, which is able to
handle full three-dimensional propagation. In this context, the development of a robust
method for 3D eigenrays search is addressed, which is fundamental for the calculation of
a channel impulse response. A remarkable aspect of the search strategy was its ability
to provide accurate values of initial eigenray launching angles, even dealing with nonlinearity
induced by the complex regime propagation of ray bouncing on the boundaries.
In the same way, a optimized method for pressure eld calculation is presented, that
accounts for a large numbers of sensors. These numerical enhancements and optimization
of the sequential version of TRACEO3D led to signi cant improvements in its performance
and accuracy. Furthermore, the present work considered the development of parallel
algorithms to take advantage of the GPU architecture, looking carefully to the inherent
parallelism of ray tracing and the high workload of predictions for 3D propagation. The
combination of numerical enhancements and parallelization aimed to achieve the highest
performance of TRACEO3D. An important aspect of this research is that validation and
performance assessment were carried out not only for idealized waveguides, but also for
the experimental results of a tank scale experiment. The results will demonstrate that
a remarkable performance was achieved without compromising accuracy. It is expected
that the contributions and remarkable reduction in runtime achieved will certainly help to
overcome some of the reserves in employing a 3D model for predictions of acoustic elds
New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs
This work presents the development of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyro-TWTs. For the first time, it is shown that the operation of such passive mode-locked helical gyro-TWTs in the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. This could be of particular interest for some new time-domain DNP-NMR methods
New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs
This work presents the development of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyro-TWTs. For the first time, it is shown that the operation of such passive mode-locked helical gyro-TWTs in the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. This could be of particular interest for some new time-domain DNP-NMR methods
Accelerating the Performance of a Novel Meshless Method Based on Collocation With Radial Basis Functions By Employing a Graphical Processing Unit as a Parallel Coprocessor
In recent times, a variety of industries, applications and numerical methods including the meshless method have enjoyed a great deal of success by utilizing the graphical processing unit (GPU) as a parallel coprocessor. These benefits often include performance improvement over the previous implementations. Furthermore, applications running on graphics processors enjoy superior performance per dollar and performance per watt than implementations built exclusively on traditional central processing technologies. The GPU was originally designed for graphics acceleration but the modern GPU, known as the General Purpose Graphical Processing Unit (GPGPU) can be used for scientific and engineering calculations. The GPGPU consists of massively parallel array of integer and floating point processors. There are typically hundreds of processors per graphics card with dedicated high-speed memory. This work describes an application written by the author, titled GaussianRBF to show the implementation and results of a novel meshless method that in-cooperates the collocation of the Gaussian radial basis function by utilizing the GPU as a parallel co-processor. Key phases of the proposed meshless method have been executed on the GPU using the NVIDIA CUDA software development kit. Especially, the matrix fill and solution phases have been carried out on the GPU, along with some post processing. This approach resulted in a decreased processing time compared to similar algorithm implemented on the CPU while maintaining the same accuracy
The Investigation of Efficiency of Physical Phenomena Modelling Using Differential Equations on Distributed Systems
This work is dedicated to development of mathematical modelling software. In this dissertation numerical methods and algorithms are investigated in software making context. While applying a numerical method it is important to take into account the limited computer resources, the architecture of these resources and how do methods affect software robustness. Three main aspects of this investigation are that software implementation must be efficient, robust and be able to utilize specific hardware resources. The hardware specificity in this work is related to distributed computations of different types: single CPU with multiple cores, multiple CPUs with multiple cores and highly parallel multithreaded GPU device. The investigation is done in three directions: GPU usage for 3D FDTD calculations, FVM method usage to implement efficient calculations of a very specific heat transferring problem, and development of special techniques for software for specific bacteria self organization problem when the results are sensitive to numerical methods, initial data and even computer round-off errors. All these directions are dedicated to create correct technological components that make a software implementation robust and efficient. The time prediction model for 3D FDTD calculations is proposed, which lets to evaluate the efficiency of different GPUs. A reasonable speedup with GPU comparing to CPU is obtained. For FVM implementation the OpenFOAM open source software is selected as a basis for implementation of calculations and a few algorithms and their modifications to solve efficiency issues are proposed. The FVM parallel solver is implemented and analyzed, it is adapted to heterogeneous cluster Vilkas. To create robust software for simulation of bacteria self organization mathematically robust methods are applied and results are analyzed, the algorithm is modified for parallel computations
Parallel computation techniques for virtual acoustics and physical modelling synthesis
The numerical simulation of large-scale virtual acoustics and physical modelling
synthesis is a computationally expensive process. Time stepping methods, such as
finite difference time domain, can be used to simulate wave behaviour in models of
three-dimensional room acoustics and virtual instruments. In the absence of any form
of simplifying assumptions, and at high audio sample rates, this can lead to simulations
that require many hours of computation on a standard Central Processing Unit
(CPU). In recent years the video game industry has driven the development of Graphics
Processing Units (GPUs) that are now capable of multi-teraflop performance using
highly parallel architectures. Whilst these devices are primarily designed for graphics
calculations, they can also be used for general purpose computing. This thesis explores
the use of such hardware to accelerate simulations of three-dimensional acoustic wave
propagation, and embedded systems that create physical models for the synthesis of
sound.
Test case simulations of virtual acoustics are used to compare the performance of
workstation CPUs to that of Nvidia’s Tesla GPU hardware. Using representative multicore
CPU benchmarks, such simulations can be accelerated in the order of 5X for
single precision and 3X for double precision floating-point arithmetic. Optimisation
strategies are examined for maximising GPU performance when using single devices,
as well as for multiple device codes that can compute simulations using billions of grid
points. This allows the simulation of room models of several thousand cubic metres
at audio rates such as 44.1kHz, all within a useable time scale. The performance of
alternative finite difference schemes is explored, as well as strategies for the efficient
implementation of boundary conditions.
Creating physical models of acoustic instruments requires embedded systems that
often rely on sparse linear algebra operations. The performance efficiency of various
sparse matrix storage formats is detailed in terms of the fundamental operations that
are required to compute complex models, with an optimised storage system achieving
substantial performance gains over more generalised formats. An integrated instrument
model of the timpani drum is used to demonstrate the performance gains that are
possible using the optimisation strategies developed through this thesis
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