A two-phase approach to fuzzy system identification is proposed. The first phase produces a baseline design to identify a prototype fuzzy system for a target system from a collection of input-output data pairs. It uses two easily implemented clustering techniques: the subtractive clustering method and the fuzzy c-means (FCM) clustering algorithm. The second phase (fine tuning) is executed to adjust the parameters identified in the baseline design. This phase uses the steepest descent and recursive least-squares estimation methods. The proposed approach is validated by applying it to both a function approximation type of problem and a classification type of problem. An analysis of the learning behavior of the proposed approach for the two test problems is conducted for further confirmation.
Tophi typically occur many years after uncontrolled gout. Therefore, their development before gout remains unusual. Such patients might exhibit some characteristic differences compared with typical tophaceous gout patients. In this study, 65 tophaceous gout patients with tophi as the first sign of gout (tophi-first group) were enrolled. Their clinical characteristics were compared with those of 1421 patients whose tophi occurred after gout (tophi-after group). Compared with the tophi-after group, the tophi-first group had a significantly higher percentage of female patients and patients with elderly onset of disease and a lower percentage of patients with a positive family history; these patients had lower body mass indices, serum urate levels, and estimated glomerular filtration rates (eGFRs). Female sex and negative family history were identified as the principal determinants of tophi development before gout. The decreasing eGFR among the tophi-first group was not due to the group per se but was a result of older age, longer tophi duration, and hyperuricemia. The most common site of initial tophi occurrence in both groups was the toe. In the tophi-first group, the occurrence rates for initial tophi sites were significantly higher at the finger but were lower at the ankle. The tophi-first group exhibited distinct characteristics of age, gender, family history, BMI, serum urate levels, and initial tophi site. This group had fewer comorbidities but similar renal dysfunction compared with the tophi-after group. Thus, patients presenting with tophi should be treated promptly, even if they have no history of gout symptoms.
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