The building of model of pressure-load character of main-pipe system is helpful to derive the calculation formula of main-pipe total steam load demand.

母管系统压力负荷特性模型的建立有助于推导母管蒸汽总负荷需求的计算公式。

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We could derive the supplier's optimum price and the consumer's optimum ordering quantity through separately establishing the profit function models of both sides of the supply and demand.

通过分别建立供需双方的利润函数模型并导出供方的最优定价和需方的最优订货量。

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But external factors have helped, too. In particular, a European Union directive requires Britain to derive 15% of its energy demand from renewables by 2020.

其中同样也有外部作用，尤其是欧盟促进可再生能源使用指令，其要求到2020年，英国必须有15%的电力来源于可再生能源。

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Corporations, especially multi-nationals that derive much of their business overseas, are facing slowing demand because of the weakening global economy, weighing on profit margins.

FORBES: FOCUS: U.S. Corporate Earning May Disappoint; Could Trip Up Stocks, Gold