Making constraint solvers more usable: overconstraint problem

The richness and expressive power of geometric constraints causes unintended ambiguities and inconsistencies during their solution or realization. For example, geometric constraint problems may turn out to be overconstrained requiring the user to delete one or more of the input constraints, and the solutions must then be dynamically updated. Without proper guidance by the constraint solver, the user must have profound insight into the mathematical nature of constraint systems and understand the internals of the solver algorithm. But a general user is most likely unfamiliar with those problems, so that the required interaction with the constraint solver may well be beyond the user's ability. In this paper, we present strategies and techniques to empower the user to deal effectively with the overconstraint problem while not requiring him or her to become an expert in the mathematics of constraint solving.We formulate this problem as a series of formal requirements that gel with other essentials of constraint solvers. We then give algorithmic solutions that are both general and efficient (running time typically linear in the number of relevant constraints).     

Estimation of Surface Flow and Net Heat Flux from Infrared Image Sequences

The study of dynamical processes at the sea surface interface using infrared image sequence analysis has gained tremendous popularity in recent years. Heat is transferred by similar transport mechanisms as gases relevant to global climatic changes. These similarities lead to the use of infrared cameras to remotely visualize and quantitatively estimate parameters of the underlying processes. Relevant parameters that provide important evidence about the models of air-sea gas transfer are the temperature difference across the thermal sub layer, the probability density function of surface renewal and the flow field at the surface. Being a driving force in air sea interactions, it is of equal importance to measure heat fluxes. In this paper we will present algorithms to measure the above parameters of air-sea gas transfer during night-time and show how to combine physical modeling and quantitative digital image processing algorithms to identify transport models. The image processing routines rely on an extension of optical flow computations to incorporate brightness changes in a total least squares (TLS) framework. Statistical methods are employed to support a model of gas transfer and estimate its parameters. Measurements in a laboratory environment were conducted and results verified with ground truth data gained from traditional measurement techniques.     

Investigations on laser sintering of ceramic slurries

For almost two decades, layer manufacturing techniques have assisted the product development at various stages from the operational point of view. Laser sintering is a powder-based layer manufacturing technology. Since the beginning of the 1990s, laser sintering of ceramic materials has been investigated academically. Since laser sintered bodies are porous correlating with a comparatively low strength, industrial use is still limited. This paper provides a knowledge base for laser sintering of ceramic suspensions. Therefore a model based on system analysis is generated, which is sub-divided into a drying and a process model. Furthermore experimental investigations with different high-performance oxide ceramic slurries (e.g., zirconia) are conducted in order to approve the estimations of the model.     

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Process components of the Implicit Association Test: A diffusion-model analysis.

The authors present a diffusion-model analysis of the Implicit Association Test (IAT). In Study 1, the IAT effect was decomposed into 3 dissociable components: Relative to the compatible phase, (a) ease and speed of information accumulation are lowered in the incompatible phase, (b) more cautious speed-accuracy settings are adopted, and (c) nondecision components of processing require more time. Studies 2 and 3 assessed the nature of interindividual differences in these components. Construct-specific variance in the IAT relating to the construct to be measured (such as implicit attitudes) was concentrated in the compatibility effect on information accumulation (Studies 2 and 3), whereas systematic method variance in the IAT was mapped on differential speed-accuracy settings (Study 3). Implications of these dissociations for process theories of the IAT and for applications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A tilting device for three-dimensional microscopy: Application to in situ imaging of interphase cell nuclei

The resolution of an optical microscope is considerably less in the direction of the optical axis (z) than in the focal plane (x-y plane). This is true of conventional as well as confocal microscopes. For quantitative microscopy, for instance studies of the three-dimensional (3-D) organization of chromosomes in human interphase cell nuclei, the 3-D image must be reconstructed by a point spread function or an optical transfer function with careful consideration of the properties of the imaging system. To alleviate the reconstruction problem, a tilting device was developed so that several data sets of the same cell nucleus under different views could be registered. The 3-D information was obtained from a series of optical sections with a Zeiss transmission light microscope Axiomat using a stage with a computer-controlled stepping motor for movement in the z-axis. The tilting device on the Axiomat stage could turn a cell nucleus through any desired angle and also provide movement in the x-y direction. The technique was applied to 3-D imaging of human lymphocyte cell nuclei, which were labelled by in situ hybridization with the DNA probe pUC 1.77 (mainly specific for chromosome 1). For each nucleus, 3-D data sets were registered at viewing angles of 0°, 90° and 180°; the volumes and positions of the labelled regions (spots) were calculated. The results also confirm that, in principle, any angle of a 2p geometry can be fixed for data acquisition with a high reproducibility. This indicates the feasibility of axiotomographical microscopy of cell nuclei.