Post-processing Functions Research Articles

PyCOOL — A Cosmological Object-Oriented Lattice code written in Python

There are a number of different phenomena in the early universe that have to be studied numerically with lattice simulations.This paper presents a graphics processing unit (GPU) accelerated Python program called PyCOOL that solves the evolution of scalar fields in a lattice with very precise symplectic integrators.The program has been written with the intention to hit a sweet spot of speed, accuracy and user friendliness. This has been achieved by using the Python language with the PyCUDA interface to make a program that is easy to adapt to different scalar field models.In this paper we derive the symplectic dynamics that govern the evolution of the system and then present the implementation of the program in Python and PyCUDA. The functionality of the program is tested in a chaotic inflation preheating model, a single field oscillon case and in a supersymmetric curvaton model which leads to Q-ball production.We have also compared the performance of a consumer graphics card to a professional Tesla compute card in these simulations.We find that the program is not only accurate but also very fast.To further increase the usefulness of the program we have equipped it with numerous post-processing functions that provide useful information about the cosmological model. These include various spectra and statistics of the fields. The program can be additionally used to calculate the generated curvature perturbation.The program is publicly available under GNU General Public License at https://github.com/jtksai/PyCOOL. Some additional information can be found from http://www.physics.utu.fi/tiedostot/theory/particlecosmology/pycool/.

Effect of Velocity of Fluid Field of 3-Spacer Nozzle in Roll-Casting Models Using Coupled Fluid-Thermal Finite Element Analysis

A finite element model of fluid field of front-box and 3-spacer nozzle of aluminum roll-casting has been developed to provide a comparison of analyzing distribution of velocity and temperature of outlet of nozzle with variable velocity. The computation is performed by using coupled fluid-thermal FEM simulation of FLOTRAN module in ANSYS 6.0. The boundary conditions of the roll-casting model of fluid and thermal fields, were loaded on front-box and nozzle. Based on the postprocessing function of ANSYS, the strict result analysis was conducted by MATLAB. Results based on the allowable inhomogeneity of velocity and temperature of outlet show the most possible broken regions of outlet could be predicted in the case of speed increasing of the drawing-sheet and thickness reducing of the aluminium sheet. The profile parameters of the nozzle including distribution, shapes and sizes of the nozzle spacers, and shapes of inner nozzle must be optimized to be appropriate in high roll cast speed.

FPGA Design of an Intra 16 × 16 Module for H.264/AVC Video Encoder

In this paper, we propose novel hardware architecture for intra 16 × 16 module for the macroblock engine of a new video coding standard H.264. To reduce the cycle of intra prediction 16 × 16, transform/quantization, and inverse quantization/inverse transform of H.264, an advanced method for different operation is proposed. This architecture can process one macroblock in 208 cycles for all cases of macroblock type by processing 4 × 4 Hadamard transform and quantization during 16 × 16 prediction. This module was designed using VHDL Hardware Description Language (HDL) and works with a 160 MHz frequency using ALTERA NIOS-II development board with Stratix II EP2S60F1020C3 FPGA. The system also includes software running on an NIOS-II processor in order to implementing the pre-processing and the post-processing functions. Finally, the execution time of our HW solution is decreased by 26% when compared with the previous work.

Analysis and Construction of Correctors

A post-processing function is used to reduce or eliminate statistical weaknesses of physical random number generators. The output bias of a n-bit input m-bit output function is examined, when the input bits are biased. For this purpose, the definition of (n, m, t)-corrector is introduced; many characterizations and properties of a corrector are presented. It appears as a generalization of the notion of resilience for a vectorial function. Several constructions of correctors from old correctors are also proposed.

Automatic segmentation of the liver from multi- and single-phase contrast-enhanced CT images

Segmentation of contrast-enhanced abdominal CT images is required by many clinical applications of computer aided diagnosis and therapy planning. The research on automated methods involves different organs among which the liver is the most emphasized. In the current clinical practice more images (at different phases) are acquired from the region of interest in case of a contrast-enhanced abdominal CT examination. The majority of the existing methods, however, use only the portal-venous image to segment the liver. This paper presents a method that automatically segments the liver by combining more phases of the contrast-enhanced CT examination. The method uses region-growing facilitated by pre- and post-processing functions, which incorporate anatomical and multi-phase information to eliminate over- and under-segmentation. Another method, which uses only the portal-venous phase to segment the liver automatically, is also presented. Both methods were evaluated using different datasets, which showed that the result of multi-phase method can be used without or after minor correction in nearly 94% of the cases, and the single-phase method can provide result comparable with non-expert manual segmentation in 90% of the cases. The comparison of the two methods demonstrates that automatic segmentation is more reliable when the information of more phases is combined.

Theory and Design of Microwave-Tube Simulator Suite

The development of microwave-tube simulator suite (MTSS) is reported. MTSS is an integrated full-featured software package for microwave-tube analysis and design. It includes a friendly user-interface module and three physics simulators. Microwave-tube design environment is the user-interface module, which provides a powerful solid-modeling front end and graphical and computational postprocessing functionality. Electron optics simulator (EOS) is a fully 3-D finite-element design tool for microwave-tube electron guns and collectors. An EOS is used to design gridded guns, multibeam guns, and anisotropic collectors. A high-frequency circuit simulator is an advanced 3-D electromagnetic (EM) simulation tool for RF components, which has two solution methods based on a finite-integration technique and a finite-element method. Beam-wave interaction simulator (BWIS) is a design tool for electron beam and EM-wave interaction in microwave tubes. The 1-D, 2-D, and 3-D multifrequency nonlinear beam-wave interactions for helix traveling-wave tubes have been implemented in BWIS. The architecture, features, theory, and design of MTSS are presented.

An efficient H.264 intra frame coder system

In this paper, we present an efficient H.264 intra frame coder system that achieves real-time performance for portable consumer electronics applications with low hardware cost. The system includes a low cost intra prediction hardware design that implements all intra prediction modes used in H.264 video coding standard based on a novel organization of the intra prediction equations. The proposed hardware is implemented in Verilog HDL. The Verilog RTL code works at 71 MHz in a Xilinx Virtex II FPGA and it can code 35 CIF (352 times 288) frames per second. The system also includes software running on an Arm926EJS processor for implementing pre-processing and post-processing functions. The H.264 intra frame coder system is demonstrated to work correctly on an Arm Versatile Platform development board and it is verified to be compliant with H.264 standard.

Clinical competence statement on thoracic endovascular aortic repair (TEVAR)—multispecialty consensus recommendations: A Report of the SVS/SIR/SCAI/SVMB Writing Committee to Develop a Clinical Competence Standard for TEVAR

Clinical competence statement on thoracic endovascular aortic repair (TEVAR)—multispecialty consensus recommendations: A Report of the SVS/SIR/SCAI/SVMB Writing Committee to Develop a Clinical Competence Standard for TEVAR

A coupled level set-boundary integral method for moving boundary simulations

A numerical method for moving boundary problems based upon level set and boundary integral formulations is presented. The interface velocity is obtained from the boundary integral solution using a Galerkin technique for post-processing function gradients on the interface. We introduce a new level set technique for propagating free boundary values in time, and couple this to a narrow band level set method. Together, they allow us to both update the function values and the location of the interface. The methods are discussed in the context of the well-studied two-dimensional nonlinear potential flow model of breaking waves over a sloping beach. The numerical results show wave breaking and rollup, and the algorithm is verified by means of convergence studies and comparisons with previous techniques. 1. Introduction and overview

New opportunities for the use of digital video in on-line radiologic curricula 1

To explore techniques to conveniently and self-sufficiently create high-quality, web-ready instructional digital video snippets suitable for routine use in on-line radiologic curricula. A commercially available digital camera with an 8-megapixel image receptor and the capability to record web-ready digital video and audio at a resolution of up to 640 x 480 pixels and a frame rate of up to 30 per second was used to obtain video snippets intended for inclusion in on-line curricula. Hand-held and tripod techniques were compared. Evaluation focused on the types of snippets deemed most likely to be used within on-line educational content, ranging in length from 10 seconds to 2 minutes. Additionally, basic postprocessing functions to experiment with combinations of video-file size, format, transmission efficiency, and image quality were used. The overall video quality was considered by participating radiologists to be good to excellent for its intended purposes. For most situations tested, a matrix size of 320 x 240 pixels provided a good balance of visual quality versus file size and transmission overhead. The 640 x 480 format was occasionally optimal, but was usually larger than necessary and resulted in substantially larger files, especially at a rate of 30 frames per second. A rate of 15 frames per second was considered adequate for most situations, regardless of matrix size, although it did add some barely discernible choppiness to the display. For all but very short snippets, a tripod or some other form of stabilization was necessary to eliminate distracting "camera shake" associated with free-hand acquisition. With a tripod, appropriate ambient lighting, and a favorable acoustical environment, videos of excellent quality when using the highest settings available on the camera (640 x 480, 30 frames/sec) could be self-sufficiently produced. However, such high-quality video with its associated large file size was rarely the optimal fit for the needs of this curricula. These results indicate that newer-generation digital cameras are useful for quickly and inexpensively producing high-quality, web-ready digital video suitable for use in on-line education.

Reduction of post-processing for stereolithography systems by fabrication-direction optimization

The surface of stereolithography parts become rough due to the stair-stepping effect and burrs from the support structure. Therefore, most parts need some finishing work for further applications. Because post-processing operations are performed by skilled workers and require additional time and cost, the reduction of post-processing time and cost is a high priority. Basic approaches to minimizing post-processing are investigated. Surface roughness is analyzed through theoretical models and experiments developing an interpolation method to predict the behavior of the roughness under various equipment conditions and fabrication styles are conducted. Part orientation is optimized by a post-processing objective function. To accelerate the optimization, a model mapping method is developed and verified. An expert system is implemented by the suggested algorithms and examined by several models in real a workshop.

A successive order of scattering model for solving vector radiative transfer in the atmosphere

A full vector radiative transfer model for vertically inhomogeneous plane–parallel media has been developed by using the successive order of scattering approach. In this model, a fast analytical expansion of Fourier decomposition is implemented and an exponent-linear assumption is used for vertical integration. An analytic angular interpolation method of post-processing source function is also implemented to accurately interpolate the Stokes vector at arbitrary angles for a given solution. It has been tested against the benchmarks for the case of randomly orientated oblate spheroids, illustrating a good agreement for each stokes vector (within 0.01%). Sensitivity tests have been conducted to illustrate the accuracy of vertical integration and angle interpolation approaches. The contribution of each scattering order for different optical depths and single scattering albedos are also analyzed.

Simultaneous derivation of intensities and weighting functions in a general pseudo-spherical discrete ordinate radiative transfer treatment

The retrieval of atmospheric constituents from measurements of backscattered light requires a radiative transfer forward model that can simulate both intensities and weighting functions (partial derivatives of intensity with respect to atmospheric parameters being retrieved). The radiative transfer equation is solved in a multi-layer multiply-scattering atmosphere using the discrete ordinate method. In an earlier paper dealing with the upwelling top-of-the-atmosphere radiation field, it was shown that a full internal perturbation analysis of the plane-parallel discrete ordinate solution leads in a natural way to the simultaneous generation of analytically-derived weighting functions with respect to a wide range of atmospheric variables. In the present paper, a more direct approach is used to evaluate explicitly all partial derivatives of the intensity field. A generalization of the post-processing function is developed for the derivation of weighting functions at arbitrary optical depth and stream angles for both upwelling and downwelling directions. Further, a complete treatment is given for the pseudo-spherical approximation of the direct beam attenuation; this is an important extension to the range of viewing geometries encountered in practical radiative transfer applications. The numerical model LIDORT developed for this work is able to generate intensities and weighting functions for a wide range of retrieval scenarios, in addition to the passive remote sensing application from space. We present a number of examples in an atmosphere with O 3 absorption in the UV, for satellite (upwelling radiation) and ground-based (downwelling radiation) applications. In particular, we examine the effect of various pseudo-spherical parameterizations on backscatter intensities and weighting functions with respect to O 3 volume mixing ratio. In addition, the use of layer-integrated multiple scatter output from the model is shown to be important for satellite instruments with wide-angle off-nadir viewing geometries.

Methodology of off-line software compensation for errors in the machining process on the CNC machine tool

Off-line software machining accuracy enhancement has been suggested based on the prediction of the machining error Δ→=[Δx,Δy,Δz]. It has been assumed that errors in the machine tool workspace can be analysed as a superposition of the components Δ→g,Δ→m,Δ→n where Δ→g results from the geometric surface description, Δ→m results from the limited machine tool stiffness and Δ→n results from the cutting tool deflection during machining.Geometric description error Δ→g=[Δxg,Δyg,Δzg] arises from the surface geometric modelling phase in the CAD system. The NURBS (Non-Uniform Rational B-Spline) technique has been selected as the most effective for the complex shape surface description, supported by the least square principle. Then the distances between the measuring points and the calculated points on the described surface patch have been determined and a function representing the inaccuracy of the surface description has been defined.The Δ→m=[Δxm,Δym,Δzm] error has been calculated based on periodic measurements of the machine tool positions while applying static forces to the spindle endpoint. The points in the factor have been selected according to principles of mathematical experiment planning.The polynomial regression-based relationships have been derived for Δ→m error description. The results have been validated using statistical correlation analysis. A similar approach has been adopted for the estimation of the cutting tool deflection error Δ→n=[Δxn,Δyn,Δzn].The resulting Δx, Δy and Δz components have been introduced as compensation values adding up to the regular tool movements along the programmed tool path. A special postprocessing program has been developed for doing this job, herein called active task in order to differentiate it from standard postprocessing functions named as passive tasks.

Numerical Simulation of Thermal Effects in Nonlinear Optical Materials

AbstractA numerical simulation of the nonlinear optical and thermal response of a material is described. The code is divided into preprocessor, simulation and postprocessing functions. The simulation function is a transient, three dimensional, finite difference algorithm which describes the thermal response and the optical phase change that occurs due to 3rd order nonlinearity and thermal effects. Irradiance changes due to linear and nonlinear absorption mechanisms are included in the code. In the postprocessing function a Gaussian beam decomposition technique is used to calculate the irradiance and transmitted power at a far field location and the temperature time response of the material. Examples of using the code to simulate Z-scan experiments are presented and compared to those reported in the literature. Results are presented that demonstrate that the code can be used as a tool to investigate using thermal transport mechanisms to modify the nonlinear optical response of the material. Limitations of the code are discussed.

Clinical relevance of scattering.

Diffuse scattering is the basic sound interaction responsible for the soft tissue detail seen in modern clinical gray scale ultrasound imaging. Its counterpart is specular reflection which is the physical interaction responsible for the bright interfaces seen in bistable and modern images. This paper will illustrate the effects of operator-controlled system variables on the image generated from diffuse scattering processes and will demonstrate the clinical aspects of diffuse scattering through the use of tissue-mimicking phantoms and normal and pathologic clinical imaging examples. Four parameters (spatial resolution, contrast resolution, texture, and speckle) influence our ability to detect focal lesions and diffuse pathologic abnormalities in the clinical setting. Signal processing in the ultrasound system and adjustment of controls by the operator affect the perception of diffuse scattering. Imaging is influenced by transducer frequency and focusing characteristics, system gain, time gain compensation, system dynamic range, preprocessing functions, post-processing functions, system power, and frame averaging. Images illustrating the effects of these parameters will be shown.

Digital path-dependent recompensation of contrast-enhanced echocardiographic images.

The regional video intensity of two-dimensional (2D) ultrasonographic images is directly affected by energy losses from the ultrasonic beam propagating between the transducer and the specific region of interest (ROI). These losses are mainly dependent on the scattering and absorption properties of the more proximal tissues. The commonly utilized automatic time-gain compensation (TGC) procedures, based on the assumption of uniform scattering and energy conversion throughout the investigated tissues and organs, seem to be largely inadequate in the contrast echocardiographic studies which attempt to quantitate the contrast enhancement of myocardial tissue. We hereby present an algorithm for the non-linear adaptive path-dependent recompensation of the ultrasonographic video intensity for the non-uniform scattering and absorption in images obtained using automatic TGC. The variable energy losses are estimated in our technique according to the reflections from the different points along the acoustic beam. The proposed algorithm is a post-processing function. It was developed considering beam attenuation by scattering and absorption and comparing correction procedures necessary with and without the assumption of uniform attenuation. We hereby present the results obtained by applying this algorithm to contrast enhanced echocardiographic images of canine hearts. The artifacts produced by the inadequate automatic TGC are essentially reduced by the recompensation procedure. The recompensation allows the observation of the changes in video intensity induced in the myocardial tissue by contrast-enhancing media, which are otherwise severely obscured by contrast transit altering the propagation effects.

The implications of three-dimensional mesh generation on the calculation of mechanical forces in magnetic devices

The implications of the methods used in mesh generation for force calculation in three-dimensional magnetic device analysis are discussed. Virtual-work and single-solution methods are compared, and the usefulness of the element topological information is considered. It is concluded that because the virtual work approach is somewhat independent of the meshing system used and the coenergy values may be derived easily in the solution process, the approach may be the method of choice for many applications requiring low-cost force calculation in three dimensions. It must be noted, however, that it can generate large errors, and the exact method of generating the models for the multiple solutions, i.e., moving nodes or changing labels, can have major effects on the overall accuracy. In general, it is more difficult to separate postprocessing functions in three dimensions from the underlying topological structures created in the postprocessor and solver, and further work in both areas is needed to develop effective calculation techniques.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>