Direct

A Direct Observation of the Use of Child Safety Seats in Metropolitan Areas of Virginia During Summer 1993

Observational surveys of child safety seat use were conducted at the request of the Transportation Safety Administration of the Department of Motor Vehicles. The present survey was conducted in the four areas of the state with the largest populations. The data were categorized as correct use, incorrect use, and no use for each seat position in the car for children judged by the survey team to require safety seats under state law. Correct child seat use was higher (51.6%) in the rear seats of cars than in the front seats (40.8%). For the entire car, only 48.9% of the children were in a correctly used child seat, 33.6% of the child occupants were not in a safety seat, and 17.5% of the seats were obviously misused. The data also showed variations in the pattern of use among the four areas of the state. The rate of incorrect use was probably underestimated by this survey. There is a need to address the problems of non-use and incorrect use through increased education and enforcement efforts on the part of the state and localities.

Device for Rapid Orientation of Crystals by Direct-image X-ray Technique

Methodologies for the Direct Digital Control of Highly Flexible Vehicles

This report presents methodologies for the direct digital control of vehicles with flexible modes. The techniques yield robust control system designs with modest or minimal requirements on the number of sensors and control actuators. the digital system techniques used include primarily the w-transforms for direct design and stability assessment, and the 'hybrid' frequency response, for assessment and understanding of digital system peculiarities. The 'sawtooth Bode' is used as the basic control system design concept. These three elements are applied to several examples, including a comprehensive case study for a fighter aircraft flight and flexible mode control system. Both continuous and discrete system designs are considered and the continuous system characteristics are contrasted with an optimal control design. This comparison pinpoints some of the features needed to make optimal control procedures more practical and mature for flexible vehicle control applications. An important step is taken in this direction by determining the nature of performance criteria which yield, for an example case, a highly robust, extremely simple controller derived from an optimal control procedure.