Comparisons of mixed systems with decreasing failure rate component lifetimes using dispersive order

2014 ◽  
Vol 31 (6) ◽  
pp. 801-808 ◽  
Author(s):  
Abdolsaeed Toomaj ◽  
Mahdi Doostparast
Keyword(s):  
Failure Rate ◽  
Dispersive Order ◽  
Decreasing Failure Rate ◽  
Mixed Systems

Is high-altitude mountaineering Russian roulette?

2013 ◽  
Vol 9 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Edward K. Cheng
Keyword(s):  
High Altitude ◽  
Failure Rate ◽  
Rate Model ◽  
Reliability Engineering ◽  
Significant Difference ◽  
Inference Techniques ◽  
Decreasing Failure Rate

AbstractWhether the nature of the risks associated with climbing high-altitude (8000 m) peaks is in some sense “controllable” is a longstanding debate in the mountaineering community. Well-known mountaineers David Roberts and Ed Viesturs explore this issue in their recent memoirs. Roberts views the primary risks as “objective” or uncontrollable, whereas Viesturs maintains that experience and attention to safety can make a significant difference. This study sheds light on the Roberts-Viesturs debate using a comprehensive dataset of climbing on Nepalese Himalayan peaks. To test whether the data is consistent with a constant failure rate model (Roberts) or a decreasing failure rate model (Viesturs), it draws on Total Time on Test (TTT) plots from the reliability engineering literature and applies graphical inference techniques to them.

Stochastic inequalities for an overflow model

1987 ◽  
Vol 24 (3) ◽  
pp. 696-708 ◽  
Author(s):  
Arie Hordijk ◽  
Ad Ridder
Keyword(s):  
Failure Rate ◽  
Lower Bounds ◽  
Approximation Method ◽  
Queueing Networks ◽  
Upper And Lower Bounds ◽  
Phase Type ◽  
Phase Type Distributions ◽  
Decreasing Failure Rate ◽  
General Method

A general method to obtain insensitive upper and lower bounds for the stationary distribution of queueing networks is sketched. It is applied to an overflow model. The bounds are shown to be valid for service distributions with decreasing failure rate. A characterization of phase-type distributions with decreasing failure rate is given. An approximation method is proposed. The methods are illustrated with numerical results.

Cluster shock models

1981 ◽  
Vol 18 (01) ◽  
pp. 104-111 ◽  
Author(s):  
Peter F. Thall
Keyword(s):  
Failure Rate ◽  
Present Note ◽  
Cluster Process ◽  
Completely Monotonic ◽  
Poisson Cluster Process ◽  
Preservation Theorem ◽  
Shock Models ◽  
Poisson Cluster ◽  
Decreasing Failure Rate ◽  
Over Time

The survival distribution of a device subject to a sequence of shocks occurring randomly over time is studied by Esary, Marshall and Proschan (1973) and by A-Hameed and Proschan (1973), (1975). The present note treats the case in which shocks occur according to a homogeneous Poisson cluster process. It is shown that if[the device surviveskshocks] =zk, 0 <z< 1, then the device exhibits a decreasing failure rate. A DFR preservation theorem is proved for completely monotonic. A counterexample to the IFR preservation theorem is given in whichis strictly IFR while the failure rate is initially decreasing and then increasing.

scholarly journals Phalangeal Osteotomy…To Perform or Not to Perform

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0001
Author(s):  
Monique Chambers ◽  
MaCalus Hogan ◽  
Dukens LaBaze
Keyword(s):  
Failure Rate ◽  
Medical Center ◽  
Academic Medical Center ◽  
Bone Cyst ◽  
Cyst Formation ◽  
Hallux Rigidus ◽  
Reconstructive Procedures ◽  
Hallux Valgus Deformity ◽  
Patient Reported ◽  
Decreasing Failure Rate

Category: Bunion Introduction/Purpose: As the hallux valgus deformity progresses, patients can get mild to moderate arthritis of the metatarsophalangeal (MTP) joint. The degenerative process of MTP arthritis results in reactive tissue formation and proliferation of osseous and cartilaginous structures. For some patients, the results in dorsal bone spurs and pain with great toe dorsiflexion of irritation from shoes. Reconstructive procedures provide a surgical option for patients to address pain and functional limitations, prior to subchondral bone cyst formation and loss of joint space. Patients who underwent cheilectomy alone have been shown to have a high failure rate and progress to advanced disease. A phalangeal dorsiflexion osteotomy has become increasingly more popular amongst foot and ankle surgeons with the hopes of decreasing failure rate and improving early outcomes. Methods: This study was a retrospective review of prospectively collected data from 385 patients treated for hallux rigidus at a large academic medical center between July 2015 and November 2016. All patients underwent either a cheilectomy or cheilectomy with phalangeal osteotomy of the MTP joint. Collected patient reported outcomes (PROs) included in this study were SF12 M, SF12P, FAAM, VAS and PASS scores. Mann-Whitney t-test was performed using GraphPad Prism version 7.0b for Mac to compare procedure groups. Exclusion criteria included poly-trauma, revision of same procedure, and lack of pre or post- operative. Results: Eighteen patients met criteria, 8 underwent cheilectomy and 10 had a cheilectomy with osteotomy procedure. The average age was 51.9 amongst the cohort, with a total of 13 female and 5 males. Patients who underwent cheilectomy with osteotomy procedure had better outcomes across all outcome measure scores. When comparing postoperative scores, cheilectomy with osteotomy patients showed significantly higher scores compared to cheilectomy alone patients: SF12-M (56 vs 36, respectively; p=0.0333), and SF12P (52 vs 30, respectively p=0.0095). VAS scores and FAAM scores showed no statistical difference between the two cohorts. Despite surgical intervention, 50% of patients who received cheilectomy alone reported more pain post-operatively compared to no reports of worsening pain in patients who received cheilectomy with osteotomy. Conclusion: Patients with moderate to severe hallux rigidus demonstrate improved functional outcomes with phalangeal osteotomy in conjunction with cheilectomy compared to cheilectomy alone. Further research with larger cohorts would be beneficial to confirm the reports of this study and expand upon aspects of care that contribute to patient satisfaction and performance.

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