Designs varied but in 1859 an improved cylindrical design was adopted for standard use nationwide.

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The speaker's cylindrical design also offers a visually appealing direct docking option.

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Solyndra investor David Prend, of Rockport Capital Partners, said Gronet's cylindrical-design innovation "is huge, because it lowers the cost per kilowatt hour" of electricity for customers.

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Researchers at MIT, led by Dr Mark Drela and tasked by NASA, have come up with a double-wide design: instead of the traditional single cylindrical body, two partial cylinders are joined together with three engines at the back of the plane between the double tail.

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Unlike conventional cylindrical batteries, the thin, compact laminated cells offer more flexibility in design applications.

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