Experimental and Numerical Studies on Spherical Roller Bearings Using Multivariable Regression Analysis

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
R. G. Desavale ◽  
R. Venkatachalam ◽  
S. P. Chavan
Keyword(s):  
Regression Analysis ◽  
Sugar Cane ◽  
High Speed ◽  
Roller Bearing ◽  
Vibration Characteristics ◽  
Multivariable Regression Analysis ◽  
Rotor Bearing ◽  
Multivariable Regression ◽  
Bearing Structure ◽  
Bearing System

Many industries make wide use of rotor bearing systems such as high speed turbines and generators. However, the vibration of antifriction rotor–bearings is a key factor in reducing the life of the bearings; thus significantly influencing the performance and working life of the whole power plant. In earlier research on the vibration characteristics of high speed rotor–bearing systems, such as in induced draft (ID) fans, an application used in sugar cane factories, the supporting antifriction bearings were simplified as a particle on a shaft with radial stiffness and damping coefficient. However, such simplification neglects the effects of the bearing structure on the vibration performance of the rotor–bearing system. This paper demonstrates the benefits of a more holistic approach and establishes a numerical model of the stiffness of the spherical roller bearing through Buckingham's π theorem (BPT). On the basis of this model, we argue for the benefits of a new dimensional analysis (DA) technique for rotor–bearing systems. Our new DA also considers the influences of the bearing structure parameters on the vibration of rotor–bearing systems. We demonstrate the effectiveness of our approach by conducting a comparative BPT study using an ID fan, a rotor–bearing system in use in sugar cane factories. We first analyzed an ID fan using the simplified model to obtain the defect frequencies and vibration amplitude responses of the ID fan system. Subsequently the same ID fan rotor was also analyzed using our new multivariable regression analysis (MVRA) approach to verify the validity of our new and holistic BPT. The results indicate that the new method we propose in this paper for the calculation of vibration characteristics of a high speed rotor–bearing (ID fan) is credible and will save time and costs by the accurate detection of imminent bearing failure.

Abstract P172: Circulating Heat Shock Protein 70 and Antiheat Shock Protein 70 Antibodies in Atrial Fibrillation: Relation with Atrial Fibrillation Type and Response to Catheter Ablation

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Jelena Kornej ◽  
Claudia Reinhardt ◽  
Jedrzej Kosiuk ◽  
Arash Arya ◽  
Gerhard Hindricks ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Regression Analysis ◽  
Catheter Ablation ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Heat Shock Protein 70 ◽  
Recurrence Rates ◽  
Multivariable Regression Analysis ◽  
Multivariable Regression ◽  
Af Recurrence

Background: HSP and anti-HSP antibodies have been associated with AF development and progression. This study investigated the possible association between circulating heat shock protein 70 (HSP70) and anti-HSP70 antibodies as well their changes and rhythm outcome after atrial fibrillation (AF) catheter ablation. Methods: In 67 patients with AF (59±11 years, 66 % male, 66 % lone AF) undergoing catheter ablation, circulating HSP70 and anti-HSP70 antibodies levels were quantified before and 6 months after catheter ablation. Serial 7-day Holter ECGs were used to detect AF recurrences. Results: At baseline, HSP70 was detectable in 14 patients (21 %), but there was no correlation between clinical or echocardiographic variables and the presence or the level of HSP70. Patients with paroxysmal AF (n=39) showed lower anti-HSP70 antibodies (median 43, IQR 28 - 62 µg/ml) than patients with persistent AF (n=28; 53, 41 - 85 µg/ml, p=.035). Using multivariable regression analysis, AF type was the only variable associated with anti-HSP70 antibodies (Beta=.342, p=.008). At 6 months, HSP70 was present in 27 patients (41 %, p<.001 vs. baseline) with an overall increase (median 0, IQR 0 - 0 vs. 0, 0 - 0.09 ng/ml, p=.029). Similarly, there was an increase of anti-HSP70 antibodies (48, 36 - 72 vs. 57, 43 - 87 µg/ml, p<.001). AF recurrence rates were higher in patients with HSP70 increase >0.025 ng/ml (32 vs. 11 %, p=.038) or anti-HSP70 antibodies increase >2.5 µg/ml (26 vs. 4 %, p=.033). Conclusion: HSP70 and anti-HSP70 antibodies may be involved in the progression of AF and AF recurrence after catheter ablation.

scholarly journals Ceftolozane-Tazobactam for the Treatment of Multidrug-Resistant Pseudomonas aeruginosa Infections: A Multicenter Study

2018 ◽  
Vol 5 (11) ◽  
Author(s):  
Jason C Gallagher ◽  
Michael J Satlin ◽  
Abdulrahman Elabor ◽  
Nidhi Saraiya ◽  
Erin K McCreary ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Regression Analysis ◽  
Clinical Success ◽  
The United States ◽  
Multidrug Resistant ◽  
Culture Collection ◽  
Severe Illness ◽  
Multivariable Regression Analysis ◽  
Multivariable Regression ◽  
Microbiological Cure

Abstract Background Multidrug-resistant Pseudomonas aeruginosa infections remain common in hospitals worldwide. We investigated the outcomes associated with the use of ceftolozane-tazobactam for the treatment of these infections. Methods Data were collected retrospectively from 20 hospitals across the United States about adults who received ceftolozane-tazobactam for the treatment of multidrug-resistant P aeruginosa infections of any source for at least 24 hours. The primary outcome was a composite of 30-day and inpatient mortality, and secondary outcomes were clinical success and microbiological cure. Multivariable regression analysis was conducted to determine factors associated with outcomes. Results Two-hundred five patients were included in the study. Severe illness and high degrees of comorbidity were common, with median Acute Physiology and Chronic Health Evaluation (APACHE) II scores of 19 (interquartile range [IQR], 11–24) and median Charlson Comorbidity Indexes of 4 (IQR, 3–6). Delayed initiation of ceftolozane-tazobactam was common with therapy started a median of 9 days after culture collection. Fifty-nine percent of patients had pneumonia. On susceptibility testing, 125 of 139 (89.9%) isolates were susceptible to ceftolozane-tazobactam. Mortality occurred in 39 patients (19%); clinical success and microbiological cure were 151 (73.7%) and 145 (70.7%), respectively. On multivariable regression analysis, starting ceftolozane-tazobactam within 4 days of culture collection was associated with survival (adjusted odds ratio [OR], 5.55; 95% confidence interval [CI], 2.14–14.40), clinical success (adjusted OR, 2.93; 95% CI, 1.40–6.10), and microbiological cure (adjusted OR, 2.59; 95% CI, 1.24–5.38). Conclusions Ceftolozane-tazobactam appeared to be effective in the treatment of multidrug-resistant P aeruginosa infections, particularly when initiated early after the onset of infection.

scholarly journals Predictors for wound healing complications and prolonged hospital stay in patients with isolated calcaneal fractures

2022 ◽  
Author(s):  
Felix Marius Bläsius ◽  
Laura Elisabeth Stockem ◽  
Matthias Knobe ◽  
Hagen Andruszkow ◽  
Frank Hildebrand ◽  
...  
Keyword(s):  
Wound Healing ◽  
Regression Analysis ◽  
Hospital Stay ◽  
Open Fractures ◽  
Predictor Variables ◽  
Calcaneal Fractures ◽  
Multivariable Regression Analysis ◽  
Low Profile ◽  
Sinus Tarsi Approach ◽  
Multivariable Regression

Abstract Purpose Surgically treated calcaneal fractures have a high risk of postoperative wound healing complications and a prolonged length of hospital stay (LOS). The aim of this study was to identify predictor variables of impaired wound healing (IWH) and LOS in surgically treated patients with isolated calcaneal fractures. Methods This retrospective cohort study analyzed data on patients aged 18 years or older who were admitted to a level I trauma center with isolated calcaneal fractures between 2008 and 2018. Multivariable regression models were used to identify predictor variables. Results In total, 89 patients (age: 45.4 years; SD: 15.1) were included. In 68 of these patients, low-profile locking plate osteosynthesis was performed, and a minimally invasive approach (MIA) (percutaneous single screws/K-wire or low-profile locking plating via a sinus tarsi approach) was applied in 21 patients. Multivariable regression analysis revealed that a higher preoperative Böhler’s angle (β = − 0.16 days/degree, 95% CI [− 0.25, − 0.08], p = 0.004) and MIA (β = − 5.04 days, 95% CI [− 8.52, − 1.56], p = 0.002) reduced the LOS. A longer time-to-surgery (β = 1.04 days/days, 95% CI [0.66, 1.42] p = 0.001) and IWH increased the LOS (β = 7.80 days, 95% CI [4.48, 11.12], p = 0.008). In a subsequent multivariable regression analysis, two variables, open fractures (OR: 14.6, 95% CI [1.19, 180.2], p = 0.030) and overweight (BMI > 24) (OR: 3.65, 95% CI [1.11, 12.00], p = 0.019), increased the risk of IWH. Conclusion Advanced treatment algorithms for open fractures are needed to reduce the risk of IWH.

Vibration Signature Analysis of a Rotor Bearing System Using Response Surface Method

2009 ◽  
Author(s):  
P. K. Kankar ◽  
Satish C. Sharma ◽  
S. P. Harsha
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
High Speed ◽  
Vibration Response ◽  
Radial Clearance ◽  
System Response ◽  
Surface Waviness ◽  
Surface Method ◽  
Rotor Bearing ◽  
Bearing System

The vibration response of a rotor bearing system is extremely important in industries and is challenged by their highly non-linear and complex properties. This paper focuses on performance prediction using response surface method (RSM), which is essential to the design of high performance rotor bearing system. Response surface method is utilized to analysis the effects of design and operating parameters on the vibration response of a rotor-bearing system. A test rig of high speed rotor supported on rolling bearings is used. Vibration response of the healthy ball bearing and ball bearings with various faults are obtained and analyzed. Distributed defects are considered as surface waviness of the bearing components. Effects of internal radial clearance and surface waviness of the bearing components and their interaction are analyzed using design of experiment (DOE) and RSM.

Nonlinear vibration characteristics of the rotor bearing system with bolted flange joints

2019 ◽  
Vol 233 (4) ◽  
pp. 910-930
Author(s):  
Yifu Zhou ◽  
Zhong Luo ◽  
Zifang Bian ◽  
Fei Wang
Keyword(s):  
Nonlinear Vibration ◽  
Time Domain ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Rolling Bearing ◽  
Vibration Characteristics ◽  
Rotor System ◽  
Rotor Bearing ◽  
Bolted Flange ◽  
Bearing System

As sophisticated mechanical equipment, the rotor system of aero-engine is assembled by various parts; bolted flange joints are one of the essential ways of joints. Aiming at the analysis of the nonlinear vibration characteristics of the rotor-bearing system with bolted flange joints, in this paper, a finite element modeling method for a rotor-bearing system with bolted flange joints is proposed, and an incremental harmonic balance method combined with arc length continuation is proposed to solve the dynamic solution of the rotor system. In order to solve the rotor system with rolling bearing nonlinearity, the alternating frequency/time-domain process of the rolling bearing element is deduced. Compared with the conventional harmonic balance method and the time-domain method, this method has the characteristics of fast convergence and high computational efficiency; solving the rotor system with nonlinear bearing force; overcome the shortcoming that the frequency–response curve of the system is too sharp to continue solving. By using this method, the influence of bearing clearance and stiffness on vibration characteristics of the rotor system with bolted flange joints is studied. The evolution law of the state of the rotor system with bolt flange is investigated through numerical simulation and experimental data. The results indicated that the modeling and solving method proposed in this paper could accurately solve the rotor-bearing system with bolted flange joints and analyze its vibration characteristics.

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