Law level of RRO(Repeatable Run Out),NRRO(Non Repe at able Run Out),and lightweight construction are a major trend in the high-speed HDD(Hard Disk Drive)sytem to reduce track misregestration and to achieve high track ...Law level of RRO(Repeatable Run Out),NRRO(Non Repe at able Run Out),and lightweight construction are a major trend in the high-speed HDD(Hard Disk Drive)sytem to reduce track misregestration and to achieve high track density,which lead to succeed in the market.However,it is not easy to r educe RRO,NRRO,and the weight of the spinning disk spindle system efficiently because lightweight construction and or bearing stiffness changes often yields a decrease in the static and dynamic stiffness of the system,and consequently hi gh vibrations may be generated as a results.Therefore,it is of importance to e valuate in advance the accurate dynamic behavior of the high speed spinning disk spindle system of a HDD sysem.This study introduces an optimum design of the high speed spinning disk spindle system of a HDD for minimum RRO,NRRO,and lightweight construction using a gene tic algorithm.The spinning disk,hub,and bearing components of a HDD system ar e modelled as appropriate finite elements respectively and their equations of mo tion are derived to construct the system equations of the whole spinning disk sp indle system of the HDD system.The RRO and NRRO responses of the spinning disk,due to exciting forces arised from ball bearing faults and rotating unbalance,are analyzed.In the design optimation,the hub thickness,the disk thickness,bearing positio ns(or bearing span)and bearing stiffness were set as design variables.The uni que objective function is obtained by multiplying an appropriate weighting facto r by multi-objective functions,such as RRO,NRRO,and the total weight of HDD the system.The constraints are maximum RRO limit,maximum weight linit,and the critical speed limit of the HDD spindle system.Results show that the RRO,NRRO,and weight are reduced by 6%,66.7%and 28%r espectively compared with the initial design of the HDD system.Therefore,thi s present study can be used for an optimum design of the spinning disk spindle s ystem of a HDD for lightweight construction and low vibrations.展开更多
Purpose The aims of this study were to propose an alternative method to assess an optimal performance improvement rate(PIR)that would be used as a tool for coaches and elite athletes willing to reach their personal be...Purpose The aims of this study were to propose an alternative method to assess an optimal performance improvement rate(PIR)that would be used as a tool for coaches and elite athletes willing to reach their personal best,mainly those seeking for national,continental or even world record(WR)in middle-distance events.We further compared the improvement rate of women vs.men of the top-10 ranked athletes in the IAAF running these middle-distance events Method The top 10 athletes in the IAAF ranking of 800 m,1500 m,and 3000 m events for each sex were assessed for their history of race times before achieving their personal record(PR).The difference between PR(‘actual’season)and the best race time in the last season was defined as the 1st season improvement rate(1-SIR),whereas the average improvement rate in the last and preceding seasons was the multi-season improvement rate(M-SIR).1-SIR and M-SIR were calculated for each athlete.Result There were sex differences in the 1500 m with a large effect size(d=−0.746)in 1-SIR(P=0.001)and very large(d=−2.249)in M-SIR(P=0.001).Women improved more than men before the PR/WR achievements in the 800 m and 1500 m events(P=0.001)and had similar improvement rates before performing PR/WR in 3000 m events(P=0.533).Conclusion Women improve more before PR/WR achievement in 800 m and 1500 m races.However,in the 3000 m men and women have similar improvement rates in previous seasons before the PR/WR achievement.展开更多
文摘Law level of RRO(Repeatable Run Out),NRRO(Non Repe at able Run Out),and lightweight construction are a major trend in the high-speed HDD(Hard Disk Drive)sytem to reduce track misregestration and to achieve high track density,which lead to succeed in the market.However,it is not easy to r educe RRO,NRRO,and the weight of the spinning disk spindle system efficiently because lightweight construction and or bearing stiffness changes often yields a decrease in the static and dynamic stiffness of the system,and consequently hi gh vibrations may be generated as a results.Therefore,it is of importance to e valuate in advance the accurate dynamic behavior of the high speed spinning disk spindle system of a HDD sysem.This study introduces an optimum design of the high speed spinning disk spindle system of a HDD for minimum RRO,NRRO,and lightweight construction using a gene tic algorithm.The spinning disk,hub,and bearing components of a HDD system ar e modelled as appropriate finite elements respectively and their equations of mo tion are derived to construct the system equations of the whole spinning disk sp indle system of the HDD system.The RRO and NRRO responses of the spinning disk,due to exciting forces arised from ball bearing faults and rotating unbalance,are analyzed.In the design optimation,the hub thickness,the disk thickness,bearing positio ns(or bearing span)and bearing stiffness were set as design variables.The uni que objective function is obtained by multiplying an appropriate weighting facto r by multi-objective functions,such as RRO,NRRO,and the total weight of HDD the system.The constraints are maximum RRO limit,maximum weight linit,and the critical speed limit of the HDD spindle system.Results show that the RRO,NRRO,and weight are reduced by 6%,66.7%and 28%r espectively compared with the initial design of the HDD system.Therefore,thi s present study can be used for an optimum design of the spinning disk spindle s ystem of a HDD for lightweight construction and low vibrations.
文摘Purpose The aims of this study were to propose an alternative method to assess an optimal performance improvement rate(PIR)that would be used as a tool for coaches and elite athletes willing to reach their personal best,mainly those seeking for national,continental or even world record(WR)in middle-distance events.We further compared the improvement rate of women vs.men of the top-10 ranked athletes in the IAAF running these middle-distance events Method The top 10 athletes in the IAAF ranking of 800 m,1500 m,and 3000 m events for each sex were assessed for their history of race times before achieving their personal record(PR).The difference between PR(‘actual’season)and the best race time in the last season was defined as the 1st season improvement rate(1-SIR),whereas the average improvement rate in the last and preceding seasons was the multi-season improvement rate(M-SIR).1-SIR and M-SIR were calculated for each athlete.Result There were sex differences in the 1500 m with a large effect size(d=−0.746)in 1-SIR(P=0.001)and very large(d=−2.249)in M-SIR(P=0.001).Women improved more than men before the PR/WR achievements in the 800 m and 1500 m events(P=0.001)and had similar improvement rates before performing PR/WR in 3000 m events(P=0.533).Conclusion Women improve more before PR/WR achievement in 800 m and 1500 m races.However,in the 3000 m men and women have similar improvement rates in previous seasons before the PR/WR achievement.
