Abstract: A method for designing a profile extrusion die is based on an analogy that exists between membrane deflection under pressure and low Reynolds number pressure driven fluid flow. The analogy is used to predict the relative shape of the die to correct for die swell or die contraction. The application of the analogy takes into consideration the characteristics of the extruder, the operating conditions, and the extrudate composition.

Abstract: An electronic viscometer having a vibrating drive in a hollow probe which oscillates along its longitudinal axis and is damped by a sample into which the probe is inserted. The viscometer has a piezoelectric crystal having a feedback electrode, a phase locked loop circuit to track the resonant frequency, drive amplifiers and buffers, and a phase compensation network to ensure that the proper phase relationship is maintained between piezoelectric drive and feedback signals.

Abstract: An electronic viscometer having a vibrating drive and a hollow probe. The hollow probe oscillates along its longitudinal axis, and is damped by a sample into which it is inserted.

Abstract: A maintenance-free, non-pneumatic rubber tire for wheels of slow-moving vehicles such as wheelchairs, push-chairs and carts has a base (14) a rim (15), side walls (13) and a tread (11) of generally constant thickness along the width of the tire. The central region of the tire has one or two continuously annular empty space(s) (16) dimensioned to control the spring constant of the tire to a desired value. The tire also contains reinforcement e.g. in the form of a layer of cord (17) or spiral wire.

Abstract: A caster wheel which enhances critical shimmy velocity so as to minimize shimmy effects in operation. Two tread surface for contact with a ground surface and a pivot assembly for pivoting the wheel about a first vertical axis displaced from a second vertical axis extending through the center point of the wheel are provided such that the separation between the two tread surfaces strategically relate via a mathematical equation to said displacement in a manner for achieving a desired critical shimmy velocity.

Abstract: This invention pertains to catheters used with human beings for drainage of any cavity and of a variety of configurations. In particular, the invention is for using a microporous material with interconnected pores of 0.5 to 5 microns diameter such as polyethylene, polypropylene, fluorocarbon or other material that will release a controlled flow or oozing for several days of a liquid from the catheter by differential thermal expansion produced by contact with the patient. The microporous structure of the catheter may be charged with or recharged with liquids such as distilled water, antiseptics, antibiotics, enzymes, etc. which are contained and retained in the interstices so that the catheter may be described as being "self-sterilizing". Also, the catheter has other desirable features including being self-lubricating for ease of insertion and removal, and offering the opportunity for the administration of medication.