This paper presents an algorithm to obtain the intersections of a free-form surface with a series of parallel planes. When sectioning the surface with parallel planes, the change of the topology of the intersection curves is caused by characteristic points of the surface. There are seven types of characteristic points: interior maximum, interior minimum, interior saddle, boundary maximum, boundary minimum, boundary max-saddle, and boundary min-saddle points. The starting points of the intersections are found efficiently and robustly using the characteristic points. The characteristic points as well as the intersection contours can be used to evaluate the machining information for process planning, to generate NC tool path for surfaces, and to generate slices for rapid prototyping.

A novel character segmentation method for printed documents is proposed in this paper. It is very difficult to process touching, overlapping and broken characters simultaneously. The strategy of our method is to adjust the binarization parameters such that broken characters can be avoided. On the contrary, adjacent characters may spread into each other seriously. Henceforth, the character segmentation problem can be focused on touching-character detection and separation. In the proposed approach, touching characters can be detected using the topological attributes of characters and the typographical relationship between characters. More specifically, the topological attributes are derived from the spatial organization of concave residua contained in the convex hull enclosing the characters. A shortest-path algorithm together with the convex-hull information is used to separate the composite. Since these features based upon the convex hull are insensitive to character fonts and sizes, the touching-character problem of various fonts and sizes can be managed even for heavily touching characters or italic-type overlapping characters without prior slant correction. The proposed method has been applied to extract isolated characters from the contents of technical journals, which contain characters of various fonts and sizes. The promising experimental results prove the practicality and feasibility of the proposed method.

In most frame-based reasoning systems, the information being manipulated is represetned using frames, but the problem-solving knowledge that manipulates the frames is represented as production rules. One problem with this approach is that rules are not always a natrual way to represent knowledge; another is that systems containing lots of rules may suffer from problems with “exponetial blowup” in the amount of computation required. This paper describes a way to address these problems by organizing the problem-solving knowledge not as rules, but in a particular kind of frame hierarchy. the approach described in this paper has been implemented in a problem-solving system called SIPP (Semi-Intelligent Process Planner), which produces plans of action for the manufacture of metal parts. the paper gives an overview of SIPP, compares its knowledge representation and problem solving methods to approaches used in other knowledge-based systems, and describes goals for further research.