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Advanced software engineering principles imply the management of quality and process based on data from measurement. Such quality management can only be performed efficiently if it is well supported with tools that are carefully s...
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Advanced software engineering principles imply the management of quality and process based on data from measurement. Such quality management can only be performed efficiently if it is well supported with tools that are carefully selected, integrated and used in the measurement program. Realizing such support is non-trivial because tools can be used in many aspects of measurement. In this paper we describe a framework for setting up measurement tool support for software development processes. The framework explicitly links important measurement concepts with tools. Furthermore, it allows companies to use their existing tools and processes and supports the incremental adoption of measurement programs. We relate our experiences with this framework in two concrete examples of introducing measurement programs.
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The software developement process and its related activities are described, implemented, analyzed, and changed by so-called Process Engineers. Process Engineers provide descriptions of software development processes to Process Pef...
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The software developement process and its related activities are described, implemented, analyzed, and changed by so-called Process Engineers. Process Engineers provide descriptions of software development processes to Process Peformers. Because the processes usually are complex, support is needed for both Process Engineers and Process Performers. This paper reports the development and application of the process modeling environment Spearmint~1. The architecture of Spearmint allows for a flexible definition and addition of views which are used for retrieving filtered and tailored prexentations of the process models. One distinct view, namely the Electronic Process Guide used for dissemination of process information and guidance of Process Performers, is discussed in more detail. The Spearmint environment has been validated in industrial process engineering cases.
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The purpose of the proposed template propagation method is to support the comparative analysis of image pairs even when large deformations (e.g. from movement) are present. Starting from a position where valid starting estimates a...
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The purpose of the proposed template propagation method is to support the comparative analysis of image pairs even when large deformations (e.g. from movement) are present. Starting from a position where valid starting estimates are known, small sub-volumes (templates) are registered rigidly. Propagating registration results to neighboring templates, the algorithm proceeds layer by layer until corresponding points for the whole volume are available. Template classification is important for defining the templates to be registered, for propagating registration results and for selecting successfully registered templates which finally represent the motion vector field. This contribution discusses a template selection and classification strategy based on the analysis of the similarity measure in the vicinity of the optimum. For testing the template propagation and classification methods, deformation fields of four volume pairs exhibiting considerable deformations have been estimated and the results have been compared to corresponding points picked by an expert. In all four cases, the proposed classification scheme was successful. Based on homologous points resulting from template propagation, an elastic transformation was performed.
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The design of parts and structures in the vehicle development process is highly influenced by strength and stiffness requirements. Under cyclic loading a change in the local stiffness of joints can be observed which motivates anal...
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The design of parts and structures in the vehicle development process is highly influenced by strength and stiffness requirements. Under cyclic loading a change in the local stiffness of joints can be observed which motivates analyses in order to tackle stiffness changes in structures. The fatigue and stiffness behaviour has been obtained for several joining techniques and material combinations: spot and seam welds, remote laser welds and high velocity bolting for steel and/or aluminium partner sheets. Specimens under shear and peel loading as well as hat profiles under torsion have been tested under constant amplitude loading. Quasi-static tests and micrographic evaluations have been conducted in order to determine material parameters and the setup of FE models. Online stiffness measurements during fatigue life have been performed. In this paper an approach to describe degradation in specimens representing a joint detail is presented. The stiffness degradation curves for the various joining techniques are compared and a numerical description of the stiffness degradation behaviour for further simulations is derived. The concept of simulating stiffness changes in conventional joining techniques is introduced. First numerical analyses of stiffness changes in spot welded specimens are presented. Several sensitivity analyses, e.g. with regard to R-ratio or loading amplitude, are performed in order to check the numerical stability of the implemented method.
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A new approach for the automatic estimation of dense 3D deformation fields is proposed. In the first step, template propagation (an advanced block matching strategy) produces not only a large set of point correspondences, but also...
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A new approach for the automatic estimation of dense 3D deformation fields is proposed. In the first step, template propagation (an advanced block matching strategy) produces not only a large set of point correspondences, but also a quantitative measure of the "registration quality" for each point pair. Subsequently, the deformation field is obtained by a method based on Wendland radial base functions. This method has been adapted to incorporate "registration quality" into regularization, where Morozov's discrepancy principle has been applied to give intuitive meaning to the regularization parameter. The main advantage of the presented algorithm is the ability to perform an elastic registration in the presence of large deformations with minimum user interaction. Applying the method, complicated respiratory motion patterns in 3D MR images of the thorax have been successfully determined. The complete procedure takes less than one hour on a standard PC for MR image pairs (256 * 256 * 75 voxels) showing a 40 mm displacement of the diaphragm.
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Intensity value-based registration is a widely used technique for the spatial alignment of medical images. Generally, the registration transformation is determined by iteratively optimizing a similarity measure calculated from the...
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Intensity value-based registration is a widely used technique for the spatial alignment of medical images. Generally, the registration transformation is determined by iteratively optimizing a similarity measure calculated from the grey values of both images. However, such algorithms may have high computational costs, especially in the case of multi-modality registration, which makes their integration into systems difficult. At present, registration based on mutual information (MI) still requires computation times of the order of several minutes. In this contribution we focus on a new similarity measure based on local correlation (LC) which is well-suited for numerical optimization. We show that LC can be formulated as a least-squares criterion which allows the use of dedicated methods. Thus, it is possible to register MR neuro perfusion time-series (128{sup}2×30 voxel, 40 images) on a moderate workstation in real-time: the registration of an image takes about 500 ms and is therefore several times faster than image acquisition time. For the registration of CT-MR images (512{sup}2×87 CT, 256{sup}2×128 MR) a multiresolution framework is used. On top of the decomposition, which requires 47 s of computation time, the optimization with an algorithm based on MI previously de-scribed in the literature takes 97 s. In contrast, the proposed approach only takes 13 s, corresponding to a speed-up about a factor of 7. Furthermore, we demonstrate that the superior computational performance of LC is not gained at the expense of accuracy. In particular, experiments with dual contrast MR images providing ground truth for the registration show a comparable sub-voxel accuracy of LC and MI similarity.
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Under cyclic loading in combination with high local stress levels a change in stiffness of connection points, e.g. spot welds, self-piercing rivets or flow drill screws can be observed. This paper introduces a numerical approach f...
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Under cyclic loading in combination with high local stress levels a change in stiffness of connection points, e.g. spot welds, self-piercing rivets or flow drill screws can be observed. This paper introduces a numerical approach for the simulation of stiffness changes in vehicle structures under multiaxial cyclic loading as a result of the stiffness degradation of individual spot welds. The basic approach is based on a conventional damage accumulation combined with a power law representing the change in the spot weld's stiffness. Instead of an accumulated damage value D a residual stiffness is set as failure criterion. Extensions to the approach are presented for its application to multiaxial loading with variable amplitudes. A conventional multiaxial fatigue test of a complete vehicle, focusing on its rear end including global stiffness and local strain measurements at the beginning, median and at the end of the test are presented and compared to the simulated results. This computation approach allows a more reliable fatigue assessment in comparison to a fatigue analysis which does not consider stiffness changes. The damage propagation after the crack initiation at an individual spot weld is represented more accurately as subsequent changes in the load paths are considered.
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