It's common to design the value of control parameters by method of trial and error, which is hard to acquire satisfactory results.

通常用试凑的方法设计控制器参数，往往难以达到最佳效果。

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Paion recently unveiled results of a midstage trial that took advantage of a new imaging method, called diffusion-perfusion MRI, to pinpoint patients best suited to receive the drug up to nine hours after a stroke.

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His firm hopes to convince the government to fund a giant clinical trial of the method on emergency room patients.

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Menasche's initial trial of the method on ten patients showed tantalizing hints of efficacy, but because there was no control group, it is impossible to tell whether the improvements seen were due to the cell transplant or to the bypass surgery the patients also received.

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