Browsing by Author "Kotze, Johan"

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    A concept model for a multi-fingered prosthetic hand
    (1997) Kotze, Johan; Nurick, Gerald N
    The various attempts by individuals to replace the hand has led to some ingenious and practical designs, but if compared to the real hand these designs are still light years behind. Till recently the most functional prostheses developed were body powered because of the simple, light weight designs. The designs for these hands have not changed must in the last few decades indicating that the design has reached its functional limit. This and the latest technology have initiated designers ' renewed interest in externally powered prostheses. Existing externally powered hands only have one degree of freedom which limits the function of hands considerably whereas practical multi-fingered hands would provide a new dimension to the functionality of prosthetic hands. For this project a concept model for a multi-fingered prosthetic hand was developed using Lego as design medium. The objective was to develop and test mechanisms as well as control strategies which can be used in a real prosthetic hand. A proper study of the human hand was done to determine its basic anatomy as well as its functioning. An extensive literature study on prosthetic and robotic hands was also done to evaluate existing designs and determine the level of existing technology. Special emphasis was laid on the anatomical design of the human hand which led to a model with a unique design. The model incorporates a tendon driven finger mechanism instead of the traditional linkage systems. This design provides an adaptable closing finger trajectory providing better grip. The model also provide actuation to all five fingers contrary to the three fingers of existing hands. This is achieved by a simple differential mechanism driving the last three fingers semi-independently with one actuator. The model also provides abduction of all fingers as well as opposition of the thumb improving the hands versatility. The hand is controlled using a personal computer and two interface boxes. Software was developed in Visual Basic to provide the user with a control analogue to that of a real myoelectric prosthesis.
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    Insurance spares, safety equipment and spare parts on ships
    (1999) Kotze, Johan
    The company periodically contracts for the building of new ships to add to its fleet. Typically, each ship is separately designed with its own unique specifications and would therefore usually not be exactly similar to any other ship. Once a ship has been built, classification thereof will be sought through one of the classification societies such as Lloyds Register of Shipping, Nippon Kaiji Kyokai, etc. to determine the class of the ship concerned. This is essential for insurance purposes and without such classification the ship would simply not be allowed to trade internationally. Although there are certain international and other regulations or industry practices governing the specification of ships, it is nevertheless up to each shipowner and his appointed naval architects and shipyards to decide on the specifications for any ship that is to be built. The ship classification societies referred to above would typically recommend that certain minimum safety equipment and spares be carried aboard any ship for the purpose of safety at sea, but do not prescribe what these should be. Each ship operator, such as this company, based on its risk profile, decides what safety equipment and spares will form part of the ship. Typically, the type of safety equipment and spares that might be included in a ship are those whose absence, if required urgently at sea, could endanger the Jives of crew or the operational safety of the ship, and would usually include: Spare anchor and chain Critical bearings, valves and pumps Spare cylinder and cylinder sleeve Propeller and tail shaft Seals, wires and pipes The components required for the construction of a ship may be supplied either by shipyard under the construction contract or by the company as so-called "Buyers' Supplies". All such costs incurred are aggregated to determine the cost of the ship.