For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtaine...For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtained at the stage of flight test. Thus, those conventional evaluation methods cannot be employed when the distribution characteristics and priori information are unknown. In this paper, the fuzzy norm method（FNM） is proposed which combines the advantages of fuzzy theory and norm theory. The proposed method can deeply dig system information from limited data, which probability distribution is not taken into account. Firstly, the FNM is employed to evaluate variable interval and expanded uncertainty from limited PSD data, and the performance of FNM is demonstrated by confidence level, reliability and computing accuracy of expanded uncertainty. In addition, the optimal fuzzy parameters are discussed to meet the requirements of aviation standards and metrological practice. Finally, computer simulation is used to prove the adaptability of FNM. Compared with statistical methods, FNM has superiority for evaluating expanded uncertainty from limited data. The results show that the reliability of calculation and evaluation is superior to 95%.展开更多
Background This study aimed to(i)provide normative data for measures of physical fitness(PF)(i.e.,muscle strength,muscle power,linear sprint speed)in 8-to 14-year-old Tunisian children and(ii)to examine sex and age gr...Background This study aimed to(i)provide normative data for measures of physical fitness(PF)(i.e.,muscle strength,muscle power,linear sprint speed)in 8-to 14-year-old Tunisian children and(ii)to examine sex and age group differences in these measures.Methods A total of 597 subjects(aged 8~14)participated in this study,the normative data for handgrip strength,jump height,and linear sprint speed were generated and collected,and the two-way analysis of variance(ANOVA)was used to identify the presence of the main effect of age,sex,an age×sex interaction for all tests.Results The two-way ANOVA showed credible age by sex interactions for all measures of PF[Effect Size(ES)ranged from 0.28 to 0.68;P<0.05].The findings indicated a main effect of age in handgrip strength,countermovement jump(CMJ)height,and linear sprint speed(all P<0.05),regardless of sex.Post hoc analyses showed early increases in handgrip strength for boys from 8 to 14 years.For CMJ height,an increase in performance was observed from 10 to 11 years(ES=0.23)and 12 to 13 years(ES=0.14)(all P<0.05).For linear sprint speed,performance enhancement was observed from 10 to 11 years(ES=1.00).In girls,an increase in handgrip strength was noted from 9 to 12 years(ES=1.00).However,the changes across age were less convincing for CMJ height and linear sprint speed tests,suggesting that differences for girls were not sup-ported by the collected data.Boys outperformed girls in all measures of PF(P<0.05).A summary of the estimated centiles of 10-and 30-m sprint speed,grip strength,and CMJ height for boys and girls allows a particular child’s test values to be compared to the norms for the group.Conclusions In summary,this study provides normative data that can be used as a tool to classify sprint speed,strength,and jump height performance in children of both sexes aged 8-14 years.展开更多
基金supported by Aeronautical Science Foundation of China (No. 20100251006)Technological Foundation Project of China (No. J132012C001)
文摘For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density（PSD） data can be obtained at the stage of flight test. Thus, those conventional evaluation methods cannot be employed when the distribution characteristics and priori information are unknown. In this paper, the fuzzy norm method（FNM） is proposed which combines the advantages of fuzzy theory and norm theory. The proposed method can deeply dig system information from limited data, which probability distribution is not taken into account. Firstly, the FNM is employed to evaluate variable interval and expanded uncertainty from limited PSD data, and the performance of FNM is demonstrated by confidence level, reliability and computing accuracy of expanded uncertainty. In addition, the optimal fuzzy parameters are discussed to meet the requirements of aviation standards and metrological practice. Finally, computer simulation is used to prove the adaptability of FNM. Compared with statistical methods, FNM has superiority for evaluating expanded uncertainty from limited data. The results show that the reliability of calculation and evaluation is superior to 95%.
文摘Background This study aimed to(i)provide normative data for measures of physical fitness(PF)(i.e.,muscle strength,muscle power,linear sprint speed)in 8-to 14-year-old Tunisian children and(ii)to examine sex and age group differences in these measures.Methods A total of 597 subjects(aged 8~14)participated in this study,the normative data for handgrip strength,jump height,and linear sprint speed were generated and collected,and the two-way analysis of variance(ANOVA)was used to identify the presence of the main effect of age,sex,an age×sex interaction for all tests.Results The two-way ANOVA showed credible age by sex interactions for all measures of PF[Effect Size(ES)ranged from 0.28 to 0.68;P<0.05].The findings indicated a main effect of age in handgrip strength,countermovement jump(CMJ)height,and linear sprint speed(all P<0.05),regardless of sex.Post hoc analyses showed early increases in handgrip strength for boys from 8 to 14 years.For CMJ height,an increase in performance was observed from 10 to 11 years(ES=0.23)and 12 to 13 years(ES=0.14)(all P<0.05).For linear sprint speed,performance enhancement was observed from 10 to 11 years(ES=1.00).In girls,an increase in handgrip strength was noted from 9 to 12 years(ES=1.00).However,the changes across age were less convincing for CMJ height and linear sprint speed tests,suggesting that differences for girls were not sup-ported by the collected data.Boys outperformed girls in all measures of PF(P<0.05).A summary of the estimated centiles of 10-and 30-m sprint speed,grip strength,and CMJ height for boys and girls allows a particular child’s test values to be compared to the norms for the group.Conclusions In summary,this study provides normative data that can be used as a tool to classify sprint speed,strength,and jump height performance in children of both sexes aged 8-14 years.
