Abstract
The prediction accuracy of bearing remaining useful life (RUL) is not high due to the unreasonable stage division of bearing performance degradation and the blindness of feature selection. ...In order to solve this problem, RUL prediction for rolling bearings using Pearson product-moment correlation coefficient (PPMCC) and Kullback–Leibler divergence (KLIC) feature selection is proposed in this paper. First, in order to divide the bearing performance degradation status more accurately, a novel performance degradation state partition method is provided based on
t
-distributed stochastic neighbor embedding and a k-means clustering algorithm. Second, multi-scale time status feature selection is implemented using PPMCC and KLIC. Finally, the above-proposed feature selection method is validated on the performance degradation data of rolling bearings provided by the University of Cincinnati platform. The results show good and stable effectiveness of the proposed method, and its superiority is demonstrated by comparison with other approaches.
Debridement, antibiotics and implant retention (DAIR) forms the primary treatment modality for early prosthetic joint infection (PJI). The KLIC score has been proposed as a risk stratification tool ...for use in predicting outcome of prosthetic knee infections. Our aim was to determine the accuracy of this scoring system at an independent tertiary PJI centre in a typical DAIR population.
Between 2008 and 2015, patients with infected knee prostheses treated with DAIR were identified. The patient notes and blood tests were reviewed retrospectively and the 'KLIC-score' was calculated and correlated with outcome. The end point for early failure was defined as: 1) the need for unscheduled surgery, 2) infection-related death ≤12 months from debridement or 3) the need for suppressive antibiotic treatment.
59 patients received DAIR procedures for knee PJI. Treatment was successful in 41 patients (69%) with early failure in 18 patients (31%). Patients deemed high-risk (KLIC-score ≥7) had notably higher failure rates (60%) than those scoring <7 (28%). No relationship can be drawn between KLIC-scores of <7 and failure rates.
The KLIC-score applied retrospectively was able to predict patients with the highest risk of early failure but provides little information in patients with scores of <7.
Debridement, antibiotic agents, and implant retention (DAIR) is a currently accepted approach for the treatment of early prosthetic joint infections (PJI). The success of a DAIR procedure has shown ...variable results throughout the published literature. Scoring systems such as the Kidney, Liver, Index surgery, Cemented prosthesis, and C-reactive protein value (KLIC) score for the selection of patients that are likely to benefit from DAIR have proved to be helpful in decision making. Our study aims to further validate the KLIC score using a large external multicentric cohort and to evaluate other risk factors for failure.
A retrospective analysis of patients with an early acute PJI who were treated with DAIR and recorded in a database of eight Spanish university hospitals was performed. According to pre-operative variables of the KLIC study, patients were categorized into five groups: group A, ≤2 points; group B, 2.5-3.5 points; group C, 4-5 points; group D, 5.5-6.5 points; and group E, ≥7 points. Failure rates were compared between groups at 60 days and after 60 days of DAIR. Further variables for risk of failure were also analyzed.
A total of 455 patients with early acute PJI were included in the analyses. At 60 days, patients presenting with pre-operative elevated C-reactive protein serum levels,
, and polymicrobial infections were associated with failure. Failure rates recorded were 12% for group A (n = 210), 18% for group B (n = 83), 26% for group C (n = 89), 24% for group D (n = 66), and 0% for group E (n = 7). Univariable analysis between consecutive groups of the KLIC score showed no differences for failure before 60 days of the DAIR procedure. Scheduled surgery and having the procedure performed by a specialized unit were also identified as important factors for DAIR success.
Our results suggest the KLIC score was not useful for predicting failure in our cohort. Furthermore, our results indicate a specialized unit should conduct DAIR procedures.
Dynamic quantile models Gourieroux, C.; Jasiak, J.
Journal of econometrics,
11/2008, Letnik:
147, Številka:
1
Journal Article
Recenzirano
This paper introduces the Dynamic Additive Quantile (DAQ) model that ensures the monotonicity of conditional quantile estimates. The DAQ model is easily estimable and can be used for computation and ...updating of the Value-at-Risk. An asymptotically efficient estimator of the DAQ is obtained by maximizing an objective function based on the inverse KLIC measure. An alternative estimator proposed in the paper is the Method of L-Moments estimator (MLM). The MLM estimator is consistent, but generally not fully efficient. Goodness-of-fit tests and diagnostic tools for the assessment of the model are also provided. For illustration, the DAQ model is estimated from a series of returns on the Toronto Stock Exchange (TSX) market index.
In this paper, we introduce the extended method of moments (XMM) estimator. This estimator accommodates a more general set of moment restrictions than the standard generalized method of moments (GMM) ...estimator. More specifically, the XMM differs from the GMM in that it can handle not only uniform conditional moment restrictions (i.e., valid for any value of the conditioning variable), but also local conditional moment restrictions valid for a given fixed value of the conditioning variable. The local conditional moment restrictions are of special relevance in derivative pricing to reconstruct the pricing operator on a given day by using the information in a few cross sections of observed traded derivative prices and a time series of underlying asset returns. The estimated derivative prices are consistent for a large time series dimension, but a fixed number of cross sectionally observed derivative prices. The asymptotic properties of the XMM estimator are nonstandard, since the combination of uniform and local conditional moment restrictions induces different rates of convergence (parametric and nonparametric) for the parameters.
The power of bootstrap and asymptotic tests Davidson, Russell; MacKinnon, James G.
Journal of econometrics,
08/2006, Letnik:
133, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The bootstrap discrepancy measures the difference in rejection probabilities between a bootstrap test and one based on the true distribution. The order of magnitude of the bootstrap discrepancy is ...the same under the null hypothesis and under non-null processes described by Pitman drift. If the test statistic is not an exact pivot, critical values depend on which data-generating process (DGP) is used to determine the null distribution. We propose using the DGP which minimizes the bootstrap discrepancy. We also show that, under an asymptotic independence condition, the power of both bootstrap and asymptotic tests can be estimated cheaply by simulation.
Weights and pools for a Norwegian density combination Bjørnland, Hilde C.; Gerdrup, Karsten; Jore, Anne Sofie ...
The North American journal of economics and finance,
2011, 2011-1-00, 20110101, Letnik:
22, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We apply a suite of models to produce quasi-real-time density forecasts of Norwegian GDP and inflation, and evaluate different combination and selection methods using the Kullback–Leibler information ...criterion (KLIC). We use linear and logarithmic opinion pools in conjunction with various weighting schemes, and we compare these combinations to two different selection methods. In our application, logarithmic opinion pools were better than linear opinion pools, and score-based weights were generally superior to other weighting schemes. Model selection generally yielded poor density forecasts, as evaluated by KLIC.
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