Browsing by Subject "Basis vector"

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    BilKristal 4.0: A tool for crystal parameters extraction and defect quantification
    (Elsevier, 2015) Okuyan, E.; Okuyan, C.
    In this paper, we present a revised version of BilKristal 3.0 tool. Raycast screenshot functionality is added to provide improved visual analysis. We added atomic distance analysis functionality to assess crystalline defects. We improved visualization capabilities by adding high level cut function definitions. Discovered bugs are fixed and small performance optimizations are made. © 2015 Elsevier B.V. All rights reserved.
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    A new OMP technique for sparse recovery
    (IEEE, 2012) Teke, Oğuzhan; Gürbüz, A.C.; Arıkan, Orhan
    Compressive Sensing (CS) theory details how a sparsely represented signal in a known basis can be reconstructed using less number of measurements. However in reality there is a mismatch between the assumed and the actual bases due to several reasons like discritization of the parameter space or model errors. Due to this mismatch, a sparse signal in the actual basis is definitely not sparse in the assumed basis and current sparse reconstruction algorithms suffer performance degradation. This paper presents a novel orthogonal matching pursuit algorithm that has a controlled perturbation mechanism on the basis vectors, decreasing the residual norm at each iteration. Superior performance of the proposed technique is shown in detailed simulations. © 2012 IEEE.
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    Off-grid sparse SAR image reconstruction by EMMP algorithm
    (IEEE, 2013) Uğur, Salih; Arıkan, Orhan; Gurbuz, A.C.
    A new and robust sparse SAR image reconstruction technique is proposed for off-grid targets in the CS framework. In the proposed approach, basis vectors corresponding to on-grid point reflectors are perturbed on a finer grid to find the appropriate bases for the reconstruction of off-grid targets. To provide efficiency of the reconstruction, the EMMP algorithm is applied to find reflectivity center locations. As demonstrated by simulations, the proposed approach significantly improves the performance of sparse SAR image reconstruction. © 2013 IEEE.
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    A tool for pattern information extraction and defect quantification from crystal structures
    (Elsevier, 2015) Okuyan, E.; Okuyan, E.
    In this paper, we present a revised version of BilKristal 2.0 tool. We added defect quantification functionality to assess crystalline defects. We improved visualization capabilities by adding transparency support and runtime visibility sorting. Discovered bugs are fixed and small performance optimizations are made. New version program summary Program title: BilKristal 3.0 Catalogue identifier: ADYU-v3-0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYU-v3-0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1868 923 No. of bytes in distributed program, including test data, etc.: 8854 507 Distribution format: tar.gz Programming language: C, C++, Microsoft.NET Framework 2.0 and OpenGL Libraries. Computer: Personal Computers with Windows operating system. Operating system: Windows XP or higher. RAM: 20-60 Megabytes. Classification: 8. Catalogue identifier of previous version: ADYU-v2-0 Journal reference of previous version: Comput. Phys. Comm. 185 (2014) 442 External routines: Microsoft.NET Framework 2.0. For the visualization tool, graphics card driver should also support OpenGL. Does the new version supersede the previous version?: Yes Nature of problem: Determining the crystal structure parameters of a material is a very important issue in crystallography. Knowing the crystal structure parameters helps the understanding of the physical behavior of material. For complex structures, particularly for materials which also contain local symmetry as well as global symmetry, obtaining crystal parameters can be very hard. Solution method: The tool extracts crystal parameters such as primitive vectors, basis vectors and identifies the space group from atomic coordinates of crystal structures. Reasons for new version: Additional features, Compatibility issues with newer development environments, Performance optimizations, Minor bug corrections. Summary of revisions:Defect quantification capability is added. The tool can process the imperfect crystal structures, finds and quantifies the crystalline defects. The tool is capable of finding positional defects, vacancy defects, substitutional impurities and interstitial impurities. The algorithms presented in [3] are used for defect quantification implementation.Transparency support is added to the visualization tool. Users are now allowed to set the transparency of each atom type individually.Runtime visibility sorting functionality is added to facilitate correct transparency computations.Visual Studio 2012 support is added. Visual Studio 2012 specific project files are created and the project is tested with this development environment.In visualization tool, an unused log file was created. This issue is corrected.In visualization tool, some OpenGL calls which are executed at every draw are changed to be executed only when they are needed, improving the visualization performance.Restrictions: Assumptions are explained in [1,2]. However, none of them can be considered as a restriction onto the complexity of the problem. Running time: The tool was able to process input files with more than a million atoms in less than 20 s on a PC with an Athlon quad-core CPU at 3.2 GHz using the default parameter values. References: [1] Erhan Okuyan, Ugur Güdükbay, Oguz Gülseren, Pattern information extraction from crystal structures, Comput. Phys. Comm. 176 (2007) 486. [2] Erhan Okuyan, Ugur Güdükbay, BilKristal 2.0: A tool for pattern information extraction from crystal structures, Comput. Phys. Comm. 185 (2014) 442. [3] Erhan Okuyan, Ugur Güdükbay, Ceyhun Bulutay, Karl-Heinz Heinig, MaterialVis: material visualization tool using direct volume and surface rendering techniques, J. Mol. Graphics Model. 50201450-60. © 2014 The Authors.