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critical power of keyhole formation in CW Nd:YAG laser deep penetration welding

China Welding 2007年第1期16卷 36-40页

作者：秦国梁齐秀堃林尚扬 Harbin Welding Institute Harbin Institute of Technology

The energy model was founded to calculate the critical power of keyhole formation by using the limit principle in CW （ continuous wave ） Nd： YAG laser deep penetration welding process. The model was validated by experiments. The results show that ＇.there are two errors between the calculated critical power of keyhole formation and that of experiments ： one is that the calculated results is less than those of experiments, which is caused by not considering the energy loss by heat conduction in the model of keyhole formation. The other is that there is 0. 9 mm error between the axis of the calculated curve of critical power with location of laser focus and that of experimental curve, which is induced by the excursion of laser focus in laser deep penetration welding. At last, the two errors were revised according to the analyses of the errors.

关键词： laser deep penetration welding keyhole formation critical power error analysis

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Repeatability and Variability of the 3-Min All-Out Test at the Subject Level

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Journal of Science in Sport and Exercise 2023年第1期5卷 77-86页

作者： Vijay Sarthy M.Sreedhara Gregory M.Mocko Randolph E.Hutchison Department of Mechanical Engineering Clemson University243 Fluor Daniel EIBClemsonSC 29634-0921USA Department of Health Sciences Furman UniversityGreenvilleSC 29613USA

Purpose The constant work-rate to exhaustion tests must be repeated several times at each work-rate to estimate subject-level trial-to-trial variance(intra-individual variability,IIV)of critical power(CP)and work capacity(W').Alternatively,these parameters and their variance can be estimated by repeating the 3-min all-out test(3MT)fewer *** purpose of this study was to propose a method to determine subject-level repeatability of the 3MT and demonstrate the need to repeat the test multiple times to estimate *** Seven cyclists performed a ramp test and four 3MTs on a *** parameters CP,W',peak power(Pp),and total work(TW)were compared across trials using repeated measures ANOVA,Bland-Altman analysis,Intraclass Cor-relation Coefficients(ICC),Typical Error(TE)of measurement,and Coefficient of Variation(CV).Results For the group,average CP and W'were 284±58 W and 10.214±3.143 *** reliability statistics,CP(ICC=0.97,TE=8 W,CV=2.94%)and W'(ICC=0.88,TE=1.11 kJ,CV=10.87%),indicated strong ***-level repeatability was determined by comparing time-to-peak power(TPp),absolute difference in Pp(δPp),and TW(δTW)for pairs of *** average IIVs estimated by the 95%confidence intervals were±15 W for CP and±1.68 kJ for W'.Conclusions Thresholds are proposed for TPp(7 s),δPp(10%),andδTW(3%)to determine subject-level repeatability of the 3MT before computing the IIV of CP and W'.It is suggested that the 3MT is repeated at least three times to estimate the IIV,which aids in personalized measurement of training improvements and performance optimization。

关键词： critical power W' 3-Min all-out test Repeatability Intra-individual variability

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