Influence of the Impeller/Guide Vane Clearance Ratio on the Performances of a Nuclear Reactor Coolant Pump

An AP1000 nuclear reactor coolant pump is considered to assess the influence of the Impeller/Guide vane clearance on the performances of this type of pumps.Experiments and numerical simulations relying on an unidirectional fluid-solid coupling approach are used to investigate the problem(stress,strain and mode of the rotor).The results reveal the relationship existing between the hydraulic performance of the nuclear reactor coolant pump and the clearance ratio.The effect of clearance ratio on the maximum equivalent stress on the back surface of the impeller blade is greater than that on the working surface(the maximum equivalent stress on the back surface of impeller blade is about three times that on the working surface).The clearance ratio has a scarce effect on the first six natural frequencies of the rotor of the nuclear reactor coolant pump.The related vibrational modes have different waveforms.

Volume-to-creatinine clearance ratio:a predictor for contrast-induced nephropathy in chronic kidney disease after primary percutaneous coronary intervention

The volume of contrast media to the creatinine clearance （V/CrCl） ratio correlate with the contrast-induced nephropathy （CIN）. The chronic kidney disease （CKD） more likely to develop CIN after primary percutaneous coronary intervention （PCI）. Objectiv has been shown to patients would be e To determine a relatively safe V/CrCl cutoff value to avoid CIN in CKD patients undergoing primary PCI. Methods We enrolled a total of 114 patients with CKD and calculated V/CrCl. Receiver-operator characteristic methods were used to identify the optimal sensitivity and specificity for the observed range of V/CrCl for CIN. We used multivariable logistic regression to assess the predictive value of V/CrCl for the risk of CIN in CKD patients. Results Overall, there were 24 cases （21%） of CIN. The baseline mean and median V/CrCl values were significantly greater among patients with CIN （mean 5.08 ±2.01, median 4.81, and interquartile range 3.53-6.33） than among those without CIN （mean 3.35 ±1.48, median 3.12, and interquartile range 2.27-4.14, P 〈 0.001）. The receiveroperator characteristic curve analysis indicated that a V/CrCl ratio of 3.62 was a fair discriminator for CIN （Cstatistic of 0.75） in CKD patients. After adjusting for other known predictors of CIN,a V/CrCl ratio 〉3.62 remained significantly associated with CIN in CKD patients（odds ratio 8.46,95% confidence interval 2.37-30.19, P 〈 0.001）. medium dose Conclusions based on the AV/CrCl ratio〉3.62 is a simple,useful indicator for determining the safe contrast pre-PCI CrCl values in CKDs.

Drum instability of thinning spinning ultra thin-walled tubes with large diameter-to-thickness ratio

In order to explore drum instability problems of thinning spinning ultra thin-walled tubes with large diameter-to-hickness ratio, experiments of thinning spinning ultra thin-walled tubes with different clearances between the mandrel and the tube were carried out. The phenomena of drum instability were analyzed. Drum instability mechanism was studied. The important influence of the mandrel-locked ring on stable thinning spinning was found. Besides, two important parameters, namely drum ratio and drum stiffness, were proposed to characterize the drum instability of spinning ultra thin-walled tubes with large diameter-to-thickness ratio. What's more, numerical simulations were applied to explore the influences of different clearance ratios and diameter-to-thickness ratios on the drum instability. As a result, it is found that the mandrel-locked ring is the key to the stability and precision of spinning; drum ratio can reflect the degree of the deformation of the tubes; drum stiffness is a comprehensive index to measure the influences of the tube's own parameters on the spinning instability; both the clearance ratio and diameter-thickness ratio have significant influences on the drum ratio and drum stiffness.