Although slightly less accurate than liver biopsy, simple noninvasive tests can reliably exclude advanced fibrosis in Chinese NAFLD patients in our center. FIB-4 index performs better than the other tests under examination.

A novel robust control design is proposed for aircraft engines. The engine is modeled as an uncertain dynamic system (UDS), whose uncertainty may be (possibly fast) time-varying. The possible value of the uncertainty is prescribed to be within fuzzy sets. This distinguishes our modelling from the Takagi-Sugeno inference system. The uncertainty is divided into matched and mismatched portions. While the matched uncertainty lies within the range space of the input matrix, the mismatched uncertainty falls outside, which poses a significant challenge for the control design. The objective is to propose a new robust control design for aircraft engines, which are subject to mismatched uncertainty. A robust control, which is deterministic and is not IF-THEN fuzzy rule-based, is designed. The control design parameter needs to be feasible, i.e., within a prescribed range. Some prescribed deterministic performances of the system are guaranteed. By taking the control cost and the performance threshold into consideration, which is under the influence of both matched and mismatched uncertainty, the unique optimal choice of the design parameter is proposed. As a result, this control design delicately blends optimality with mismatched uncertainty. This design is applied to a turbofan engine. Hardwarein-the-loop (HIL) laboratory testing in the flight envelope demonstrates the superiority of the control design. Index Terms-Aircraft engine, robust control, fuzzy system, mismatched uncertainty, optimal design, hardware-inthe-loop testing I. INTRODUCTIONA IRCRAFT engines play an important role in both civil and military applications [1]. At present, with increasing improvements in engine performance, such as higher thrustweight ratio, economic efficiency, and security, aircraft engines have become increasingly sophisticated. This sophistication has enhanced the inherent and significant coupling and promoted the development of multivariable control.

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