Theoretical Study on Static Performance of Double-Bump Foil Bearings

In this paper, single-bump foil models with different thickness and double-bump foil models with different initial clearances are established. The structural stiffness and equivalent viscous damping of double-bump foil and single-bump foil are analyzed by finite element simulation. The results show that the double-layer bump foil has variable stiffness and the displacement of the upper bump is greater than the initial gap when the two-layer bumps contact. A model for obtaining static characteristics of aerodynamic compliant foil thrust bearing is established on the basis of the stiffness characteristics of the double-bump foil. This paper solves gas Reynolds equation, the gas film thickness equation and the foil stiffness characteristic equation via the finite element method and the finite difference method. The static characteristics of the thrust bearings including the bearing pressure distribution, the gas film thickness and the friction power consumption have been obtained. The static characteristics of two kinds of foils have been compared and analyzed, and the effect of initial clearance on the static performance of double-bump foil bearings is studied. The results show that the double-bump foil structure can effectively improve the load capacity of thrust bearing. In addition, the static performance of double-bump foil thrust bearings is between the performance of the single-bump foil bearing and the double-bump foil bearing whose foil’s clearance is zero. The smaller the initial clearance is, the easier it will be to form a stable double-bump foil supporting structure.

DOP74 Initial Clearance of infliximab is a predictor for the time of formation of anti-drug antibodies

Background Treating patients with biologics like infliximab (IFX), may cause the formation of antidrug antibodies (ADA). ADA are associated with faster drug clearance, reduced treatment efficacy and increased risk of infusion-related side effects. The aim of this study is to identify possible predictors for ADA-formation. Methods A time to first detection of ADA model was developed by using data from a Phase 3 clinical trial of biosimilar CT-P13 and originator infliximab comparing efficacy and safety in moderately to severely active Crohn’s disease (CD). We analyzed data from 220 patients initiating IFX. Seven subjects with ADA present at baseline were discarded. The following baseline covariates were evaluated in this analysis: age, weight, first estimated drug clearance, disease duration, dose, sex and concomitant immune-modulators. Continuous covariates were divided into lower quartile, inter-quartile range, and upper quartile bins. Kaplan-Meier survivor estimates were plotted by bin. The data was then modeled parametrically with NONMEM by constructing a full model which was further refined using the Wald’s Approximation Method algorithm. Hazard ratios and probability of ADA at time points of interest were calculated for significant covariates. Results Initial IFX clearance, concomitant immunomodulators and IFX dose were identified as being statistically significant predictors of the time to first ADA. The model suggested that the hazard of ADA increases by 61% for every increase on 0.1 L/day in clearance, it decreases by 41% with concomitant administration of immunomodulators and decreases by 29% for every increase in dose of 100 mg. Thus, for a patient with initial IFX clearance of 0.2 L/day, no immunomodulators and a dose of 328 mg, the average time to first ADA is 374 days (range 221–451). If clearance is 0.4 L/day under the same conditions, then ADA onset is 144.5 days (range 90–216). Increasing the starting dose to 428 mg would improve the time to onset to 203 days (range 110–337). Again, under the same conditions, adding immunomodulator would increase the time to onset to 354 days (range 214–451). Conclusion We have identified initial infliximab clearance as an independent predictor for onset of ADA in CD patients. Our results suggest that early assessment of clearance should guide treatment optimization with IFX in patients with CD, including the addition of concomitant immunosuppressants or increasing the dose during induction.

Ceftriaxone as an Alternative Therapy for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteremia after Initial Clearance of Bloodstream Infection

Introduction. Staphylococcus spp. represent the leading cause of hospital-acquired infections and second-most frequent pathogen in bloodstream infections. Methicillin-susceptible S. aureus (MSSA) comprise approximately half of all S. aureus isolates. Standard-of-care therapies (SOCTs) display high treatment success but require frequent dosing, are problematic in penicillin allergic patients, and are nephrotoxic. Ceftriaxone may represent an alternative treatment option. Methods. Adult patients hospitalized from January 2015 through June 2016 with positive MSSA blood cultures and treated with SOCT or ceftriaxone for ≥48 hours were included. Exclusion criteria were receipt of vancomycin or concomitant systemic antimicrobials with activity against MSSA, polymicrobial infections, and pregnant patients. Additional data collected included demographics, source/site of infection, and treatment. The primary endpoint was clinical cure (normalization of white blood cell count and temperature within 7 days and clearance of bloodstream within 7 days). Readmission within 60 days, length of stay, and discharge disposition were collected. Results. A total of 43 patients were included: 23 receiving SOCT and 20 receiving ceftriaxone group. Sixteen patients received SOCT prior to ceftriaxone while 4 patients were initiated on ceftriaxone. Clinical cure was observed in 18/23 (78%) and 10/20 (50%), respectively ( P = 0.052 ). Clinical failure was driven by leukocytosis despite clearance of their bloodstream infection in 3/23 (13%) SOCT group compared to 8/20 (40%) in the ceftriaxone group ( P = 0.043 ). Six patients (SOCT: 2, ceftriaxone: 4; p = 0.669 ) had infection-related readmissions, and 1 death per group was observed. Conclusion. Ceftriaxone poses a reasonable alternative to consider for MSSA bacteremia when cost and feasibility are concerns for outpatient parenteral therapy after initial clearance of bloodstream infections.

EFFECT OF THE RIVET-HOLE TOLERANCE ON THE STRESS-SEVERITY FACTOR

This work is focused on a quantitative procedure for estimating the generally unfavourable effects that incorrectly drilled holes, characterized by the initial clearance between a rivet and a hole, have on the fatigue life of riveted joints. The solution is based on an analytical approach using the stress-severity-factor concept. An experimental programme with riveted-joint specimens characterized by low-load transfer factors was realized in the Czech Aerospace Research Centre (VZLU) test lab under constant amplitude loading. The holes for rivet joints with 4-mm diameters were prepared with the clearance in a range of 0.0–0.16 mm. Force-controlled riveting was applied using a constant pressure force to form the driven head. To prevent fretting events between the joined parts, their anodized contact surfaces were lubricated with MOLYKA, plastic grease with molybdenum disulphide and graphite. The experimental data showed that the load-transfer factor and the fatigue life depend on the initial clearance between a rivet and a hole. The presented procedure introduced the hole-filling factor, integrated in the stress-severity-factor concept as a function of the initial clearance between a rivet and a hole.

An improved model for investigating the vibration characteristics of ball bearing owing to outer race waviness under high speed

In this study, an improved model for a ball bearing is established to investigate the vibration response characteristics owing to outer race waviness under an axial load and high speed. The mathematical ball bearing model involves the motions of the inner ring, outer ring, and rolling elements in the radial XY plane and axial z direction. The 2Nb + 5 nonlinear differential governing equations of the ball bearing are derived from Lagrange's equation. The influence of rotational speed and outer race waviness is considered. The outer race waviness is modeled as a superposition of sinusoidal function and affects both the contact deformation between the outer raceway and rolling elements and initial clearance. The MATLAB stiff solver ODE is utilized to solve the differential equations. The simulated results show that the axial vibration frequency occurred at l fc and the radial vibration frequencies appeared at l fc fc when the outer race waviness of the order (l) was the multiple of the number of rolling elements (k Nb) and that the principal vibration frequencies were observed at l fc fc in the radial x direction when the outer race waviness of the order (l) was one higher or one lower than the multiple of the number of rolling elements (k Nb 1). At last, the validity of the proposed ball bearing model was verified by the high-speed vibration measurement tests of ball bearings.

The Insulin Receptor Mediates Insulin’s Early Plasma Clearance by Liver, Muscle, and Kidney

The role of the insulin receptor in mediating tissue-specific insulin clearance in vivo has not been reported. Using physiologic insulin doses, we measured the initial clearance rate (first 5 min) of intravenously injected ([125I]TyrA14)-insulin by muscle, liver, and kidney in healthy rats in the presence and absence of the insulin receptor blocker S961. We also tested whether 4 weeks of high-fat diet (HFD) affected the initial rate of insulin clearance. Pre-treatment with S961 for 60 min prior to administering labeled insulin raised plasma ([125I]TyrA14)insulin concentration approximately 5-fold (p < 0.001), demonstrating receptor dependency for plasma insulin clearance. Uptake by muscle (p < 0.01), liver (p < 0.05), and kidney (p < 0.001) were each inhibited by receptor blockade, undoubtedly contributing to the reduced plasma clearance. The initial plasma insulin clearance was not significantly affected by HFD, nor was muscle-specific clearance. However, HFD modestly decreased liver clearance (p = 0.056) while increasing renal clearance by >50% (p < 0.01), suggesting a significant role for renal insulin clearance in limiting the hyperinsulinemia that accompanies HFD. We conclude that the insulin receptor is a major mediator of initial insulin clearance from plasma and for its clearance by liver, kidney, and muscle. HFD feeding increases renal insulin clearance to limit systemic hyperinsulinemia.

Flow analysis of conical spiral mandrel dies

Spiral dies are divided into three categories, namely: Flat Spiral Die (FSD), Cylindrical Spiral Mandrel Die (SMD), and Conical Spiral Mandrel Die (CSD). These dies are used to produce films via blown film extrusion and multilayer films via co-extrusion. The goal is to improve the flow distribution and to decrease the pressure drop which will result in uniform film thickness and reduced energy dissipation. A viscous power-law fluid model shows that low-pressure drop and proper flow distribution can be achieved in a CSD simultaneously. As the number of grooves and the initial channel depth increases, the flow distribution becomes more uniform and the pressure drop decreases. Also, there is an optimum initial clearance and clearance increment angle. The model results show that the pseudo-plastic fluid has more appropriate performance than the Newtonian and dilatant fluids in improving the flow distribution and reducing the pressure drop.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.