The purpose of this study was to effectively identify parameters for a LuGre friction model based on experimental measures. In earlier work related to this study (Yang et al., 2009), which was based on the characters of polygonal wear (Sueoka and Ryu, 1997), we showed a frictional vibration model for a mass on a moving belt. This model reflected lateral vibrations caused by velocity and toe-in angle. An important aspect of the present study is the improved friction model. A previous friction model, which divided the process into four parts, expressed the sable excited vibration well but failed to reflect the hysteresis loop change when vehicles accelerated or decelerated continuously. A LuGre friction model can solve this problem, but several model parameters must be obtained experimentally. We measured contact width and length of tires as vertical pressure changed; this provided a theoretical basis for apparent stiffness of a unit of tire tread. Based on tire data from Bakker E's article in a SAE paper from 1987, we identified the Stribeck exponent and Stribeck velocity in LuGre. Then, the results were implemented in a vibration system that verified the rationality of the data.
operating characteristics (ROC) analysis was used to determine the optimal cutpoint for dosimetric parameters. Results: We included 138 cases: 73 men (53.0%); median age 63 years (range, 42-83); predominantly NSCLC (N Z 114, 82.6%). Most patients received either platinum/etoposide (N Z 83, 60.1%) or carboplatin/taxol (N Z 48, 34.8%). Median RT dose was 61.2 Gy (range, 45-70 Gy). The rate of HT3+ was 41.3% (n Z 57). Increasing mean TVB dose (per Gy) was associated with a higher odds of developing HT3+ (OR Z 1.06, 95% CI Z 1.01-1.10, P Z 0.012). Increasing TVB V5-V40 was all significantly correlated with increased odds of developing HT3+. ROC analysis found that the optimal cutpoint for mean TVB dose was 23 Gy. The OR for developing HT3+ was 2.80-fold higher in patients with mean TVB dose >23 Gy compared to 23 Gy (95% CI Z 2.80-5.63, P Z 0.001). On multivariate analysis, increasing mean TVB dose, increasing age, and decreasing BMI were all statistically significantly associated with increased odds of developing HT3+. When excluding patients with SCLC, mean TVB dose and V5-V20 remained significantly associated with HT3+. Conclusion: We found that increasing TVB dose was associated with clinically significant HT in patients with lung cancer treated with CRT. This suggests that efforts to spare dose to the TVB may reduce rates of HT and potentially improve patient outcomes. Further prospective validation of these results is needed.
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