Search

Non-uniqueness of the tree representations is a well-known problem in feature extraction from the output of a CSG solid modelling system. Three main causes of the problem are examined and the most commonly occured one is dealt with in this paper. Based on the achievement of position relationships between orthogonal primitive objects, an approach for solving the non-uniqueness steming from multiple definitions for an identical object is detailed. To demonstrate the methodology of the approach, an object with the machining feature of a square slot is illustrated.

Semi-analytic formulations have previously been used for a number of stressing problems wherein axisymmetric structures have supported non-axisymmetric loads. The approach is here shown to be very useful for circular plates, and to have especial value for design analyses using desk top computers in which the main store is relatively small.

An infrared method is described for determining the fenitrothion [OO-dimethyl-O-(3-methyl-4-nitrophenyl)-phosphorothioate] content of technical material after chromatography over silica gel. The fenitrothion is eluted with methylene chloride, and after evaporating the eluate to dryness the residue is dissolved in carbon disulphide to give a concentration of fenitrothion in the range 0·8 to 1·1 per cent. w/v. Measurements taken at three absorption peaks in conjunction with related minima are used to calculate the fenitrothion content from previously prepared calibration graphs that relate absorbance to fenitrothion content.The standard deviation of this method, based on ten samples of technical material, is 0·53 per cent.