围绕扩大天然气的传播将根据加州的上限和交易制度，以明年生效，这将增加至少50美分，至每百万英国热量单位的天然气为燃料的蒸汽成本。
The spread over natural gas will widen under California's cap and trade system, set to take effect next year, which will add at least 50 cents per million BTUs to the cost of gas-fired steam.
蒸汽的高成本、加上货运对速度的低需求，使得世界上大多数的海运货物都是通过帆船来运输的，直到20世纪初，这一状况才有所改变。
The high cost of steam and the lesser need for speed kept the majority of the world's ocean freight moving by sail until the early years of the 20th century.
降低的成本也有助于那些能够生产不同形状和尺寸的成品铁制品的蒸汽动力轧钢厂的发展。
Reduced cost was also instrumental in developing steam-powered rolling mills capable of producing finished iron of various shapes and sizes.
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