A new robust optimal design methodology has been developed and applied to the design of plastic injection molding products. Taguchi's robust design method and an optimal design search algorithm are integrated with a commercial CAE simulation tool. A direct search-based optimization procedure is implemented with the considerations of process variations as well as uncontrollable noise variables. The Interactive Design Space Reduction Method (IDSRM) based on orthogonal arrays for design of experiments is developed as a general optimization tool. Using the system, designers can interactively adjust the design space during the searching process for the optimal solution based on the outcomes of the experiments. The developed methodology is applied to an industrial application: a molding process design of an automobile front bumper to minimize the weldline, a form defect of plastic parts. Compared with the initial design solution, the optimized design aided by the proposed methodology shows a more efficient and better result in terms of design robustness against process variations.
Azurin, a small blue copper protein from the bacterial species Pseudomonas aeruginosa, is mostly a beta-sheet protein arranged into a single domain. Previous folding studies have shown that the equilibrium denaturation of the holoprotein follows a two-state process; however, upon removal of the copper, the denaturation had been reported to follow a three-state process. The two unfolding transitions measured for apoazurin had been thought to arise from two different folding domains. However, in the present work, we found that the denaturation of apoazurin occurs over a single transition and we determined the folding free energy to be -27.8 +/- 2.4 kJ mol(-1). From this measurement along with measurements previously reported for the unfolding of the holoazurin, we were able to determine that Cu(II) and Cu(I) stabilize the native structure by 25.1 +/- 6.9 kJ/mol and 12.9 +/- 8.1 kJ/mol, respectively. It is our contention that the second transition displayed in the denaturation curves previously reported for apoazurin arise from protein heterogeneity-in particular, from the presence of Zn(II) azurin. We extended our investigation into the denaturation of Zn(II) azurin at pH 6.0 and 7.5. The equilibrium denaturation studies show that the zinc ion significantly stabilizes the native-state structure at pH 7.5 and very little at the lower pH. We attribute the decrease in the stabilizing effect of the zinc ion with decreasing pH to the protonation of two histidinyl side chains. When protonated the ligands, His 46 and His 117, are incapable of binding a metal ion. Further, comparing the denaturation curves of Zn(II) azurin measured by circular dichroism with those measured by fluorescence indicates that the denaturation of Zn(II) azurin is far less simple than the denaturation of apoazurin.
Most engineering software tools use typical menu-based user interfaces, and they may not be suitable for learning tools because the solution processes are hidden and students can only see the results. An educational tool for simple beam analyses is developed using a pen-based user interface with a computer so students can write and sketch by hand. The geometry of beam sections is sketched, and a shape matching technique is used to recognize the sketch. Various beam loads are added by sketching gestures or writing singularity functions. Students sketch the distributions of the loadings by sketching the graphs, and they are automatically checked and the system provides aids in grading the graphs. Students receive interactive graphical feedback for better learning experiences while they are working on solving the problems.
A feature-based CAD system must support multiple feature representations in the concurrent engineering environment in which multiple engineering groups work on a same product simultaneously. Users must be able to define customized features interactively, for different users need different feature sets. On the other hand, to share high-level information stored in features among different engineering groups, the features must be standardized to be compatible among highly customized feature sets. To solve the two conflicting requirements, a feature conversion system architecture including an interactive feature extraction module has been developed and implemented. Sharing the same basis of fundamental features, multiple feature representations can be maintained in the system. In this paper, an intermediate feature representation based on B-rep entities will be addressed for a feature conversion architecture. For the one-to-one mapping cases, a feature shape code matching mechanism is used, and a constraint-based feature extraction method is advocated for the feature conversion problem.
Solids-based Computer-Aided Design (CAD) systems are essential tools for detailed designs of mechanical components and assemblies. At the conceptual design stage, however, designers still prefer freehand sketches on paper. Sketch-based computer interfaces can be an alternative tool bridging the gap, and many attempts have been made to reconstruct 3D models from 2D sketches or drawings. Among the reconstruction methods, inflating cubic corners is one of attractive tools due to its simple and analytic nature. However, it can only handle limited regular polyhedrons whose planes are all mutually perpendicular. An extended cubic corner algorithm is developed so that linear swept volumes of arbitrary polygonal profiles can be reconstructed. The recognized swept volumes can be easily converted to feature-based parametric CAD models for further detailed designs.
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