Comprehensive Reliability Allocation Method for CNC Lathes Based on Cubic Transformed Functions of Failure Mode and Effects Analysis

Reliability allocation of computerized numerical controlled（CNC）lathes is very important in industry.Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components,which is not applicable in some conditions.Aiming at solving the problem of CNC lathes reliability allocating,a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis（FMEA）is presented.Firstly,conventional reliability allocation methods are introduced.Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated.Subsequently,a cubic transformed function is established in order to overcome these limitations.Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence.Designers can choose appropriate transform amplitudes according to their requirements.Finally,a CNC lathe and a spindle system are used as an example to verify the new allocation method.Seven criteria are considered to compare the results of the new method with traditional methods.The allocation results indicate that the new method is more flexible than traditional methods.By employing the new cubic transformed function,the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.

Alterations in renal function in patients with obstructive sleep apnea syndrome and effects of continuous positive airway pressure

Objective To assess renal function in patients with obstructive sleep apnea syndrome (OSAS) during two nights when they were untreated and treated with continuous positive airway pressure (CPAP). Methods Tubular function was estimated on the basis of the renal lithium clearance and its derived formulae, urinary osmolality, osmolal clearance and free water clearance; while glomerular function was evaluated by endogenous creatinine clearance. Twenty patients with OSAS and sixteen normal controls were studied. Results The untreated patients with OSAS had significantly lower fractional proximal tubular sodium reabsorption (59.1%±7.1%,P<0.001 vs controls), lower fractional distal tubular sodium reabsorption (93.8%±1.7%, P<0.05 vs controls) and urinary osmolality (573.0±107.9 mosm·kg 1 , P<0.05 vs controls). The absolute distal tubular reabsorption rate of sodium and osmolal clearance in the untreated patients were higher 47.0±26.0 mmol·L 1 and 25.0±4.1 ml·L 1 ; P< 0.01 and P<0.05 respectively vs controls). During CPAP treated nights all abnormal renal function indexes in the OSAS patients restored to normal control values (P>0.05). Conclusions The natriuresis and diuresis of OSAS patients were due to the decrease in proximal and distal tubular sodium reabsorption and in tubular concentration ability during their nocturnal sleep and were returned to normal by CPAP therapy.