scholarly journals Optimal Time Interval Selection in Long-Run Correlation Estimation

2006 ◽  
Author(s):  
Pedro H. Albuquerque
Keyword(s):  
Optimal Time ◽  
Time Interval ◽  
Long Run ◽  
Correlation Estimation ◽  
Interval Selection

An optimal inspection and replacement policy for a deteriorating system

1986 ◽  
Vol 23 (04) ◽  
pp. 973-988 ◽  
Author(s):  
Masamitsu Ohnishi ◽  
Hajime Kawai ◽  
Hisashi Mine
Keyword(s):  
Markov Process ◽  
Optimal Policy ◽  
Continuous Time ◽  
Average Cost ◽  
Control Limit ◽  
Replacement Policy ◽  
Optimal Time ◽  
Time Interval ◽  
Long Run ◽  
Monotonic Properties

This paper investigates a system whose deterioration is expressed as a continuous-time Markov process. It is assumed that the state of the system cannot be identified without inspection. This paper derives an optimal policy minimizing the expected total long-run average cost per unit time. It gives the optimal time interval between successive inspections and determines the states at which the system is to be replaced. Furthermore, under some reasonable assumptions reflecting the practical meaning of the deterioration, it is shown that the optimal policy has monotonic properties. A control limit rule holds for replacement, and the time interval between successive inspections decreases as the degree of deterioration increases.

An optimal inspection and replacement policy for a deteriorating system

1986 ◽  
Vol 23 (4) ◽  
pp. 973-988 ◽  
Author(s):  
Masamitsu Ohnishi ◽  
Hajime Kawai ◽  
Hisashi Mine
Keyword(s):  
Markov Process ◽  
Optimal Policy ◽  
Continuous Time ◽  
Average Cost ◽  
Control Limit ◽  
Replacement Policy ◽  
Optimal Time ◽  
Time Interval ◽  
Long Run ◽  
Monotonic Properties

This paper investigates a system whose deterioration is expressed as a continuous-time Markov process. It is assumed that the state of the system cannot be identified without inspection. This paper derives an optimal policy minimizing the expected total long-run average cost per unit time. It gives the optimal time interval between successive inspections and determines the states at which the system is to be replaced. Furthermore, under some reasonable assumptions reflecting the practical meaning of the deterioration, it is shown that the optimal policy has monotonic properties. A control limit rule holds for replacement, and the time interval between successive inspections decreases as the degree of deterioration increases.

An optimal inspection and replacement policy for a deteriorating system

1986 ◽  
Vol 23 (04) ◽  
pp. 973-988 ◽  
Author(s):  
Masamitsu Ohnishi ◽  
Hajime Kawai ◽  
Hisashi Mine
Keyword(s):  
Markov Process ◽  
Optimal Policy ◽  
Continuous Time ◽  
Average Cost ◽  
Control Limit ◽  
Replacement Policy ◽  
Optimal Time ◽  
Time Interval ◽  
Long Run ◽  
Monotonic Properties

This paper investigates a system whose deterioration is expressed as a continuous-time Markov process. It is assumed that the state of the system cannot be identified without inspection. This paper derives an optimal policy minimizing the expected total long-run average cost per unit time. It gives the optimal time interval between successive inspections and determines the states at which the system is to be replaced. Furthermore, under some reasonable assumptions reflecting the practical meaning of the deterioration, it is shown that the optimal policy has monotonic properties. A control limit rule holds for replacement, and the time interval between successive inspections decreases as the degree of deterioration increases.

The impact of the workability of an automated technological system on the effective implementation of the production program when processing tools in glow discharge plasma generators

2021 ◽  
pp. 58-65
Author(s):  
V.A. Logvin ◽  
◽  
S.A. Sheptunov ◽  
Keyword(s):  
Glow Discharge ◽  
Discharge Plasma ◽  
Functional Dependence ◽  
Plasma Generator ◽  
Glow Discharge Plasma ◽  
Optimal Time ◽  
Time Interval ◽  
Production Program ◽  
The Impact ◽  
Plasma Generators

The conditions for the hardening of tools in accordance with the author’s technological routes in the optimal time interval are considered using the functional dependence of the serviceability of plasma generators. This dependence takes into account the workability of the technical devices involved in processing the laying batch of tools in the speci ed time interval. The probability of performing the production process in the estimated time is represented by the product of the trouble-free operation of each glow discharge plasma generator involved in the nishing processing of tools that require a different type of plasma exposure in a certain sequence and duration.

Autologous Blood Pleurodesis: What Is the Optimal Time Interval and Amount of Blood?

2021 ◽  
Author(s):  
Alessio Campisi ◽  
Andrea Dell'Amore ◽  
Yonghui Zhang ◽  
Zhitao Gu ◽  
Angelo Paolo Ciarrocchi ◽  
...  
Keyword(s):  
Chest Tube ◽  
Autologous Blood ◽  
Optimal Time ◽  
Time Interval ◽  
Air Leak ◽  
Increased Risk ◽  
Tube Removal ◽  
Blood Patch ◽  
Prolonged Air Leak ◽  
Chest Tube Removal

Abstract Background Air leak is the most common complication after lung resection and leads to increased length of hospital (LOH) stay or patient discharge with a chest tube. Management by autologous blood patch pleurodesis (ABPP) is controversial because few studies exist, and the technique has yet to be standardized. Methods We retrospectively reviewed patients undergoing ABPP for prolonged air leak (PAL) following lobectomy in three centers, between January 2014 and December 2019. They were divided into two groups: Group A, 120 mL of blood infused; Group B, 60 mL. Propensity score-matched (PSM) analysis was performed, and 23 patients were included in each group. Numbers and success rates of blood patch, time to cessation of air leak, time to chest tube removal, reoperation, LOH, and complications were examined. Univariate and multivariate analysis of variables associated with an increased risk of air leak was performed. Results After the PSM, 120 mL of blood is statistically significant in reducing the number of days before chest tube removal after ABPP (2.78 vs. 4.35), LOH after ABPP (3.78 vs. 10.00), and LOH (8.78 vs. 15.17). Complications (0 vs. 4) and hours until air leak cessation (6.83 vs. 3.91, range 1–13) after ABPP were also statistically different (p < 0.05). Air leaks that persisted for up to 13 hours required another ABPP. No patient had re-operation or long-term complications related to pleurodesis. Conclusion In our experience, 120 mL is the optimal amount of blood and the procedure can be repeated every 24 hours with the chest tube clamped.

Variation of patient characteristics, management, and outcome with timing of surgery for aneurysmal subarachnoid hemorrhage

2011 ◽  
Vol 114 (4) ◽  
pp. 1045-1053 ◽  
Author(s):  
Kelly B. Mahaney ◽  
Michael M. Todd ◽  
James C. Torner
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Management Practices ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Timing Of Surgery ◽  
Early Surgery ◽  
Outcome Variable ◽  
Optimal Time ◽  
World Federation ◽  
Time Interval ◽  
Fisher Grade

ObjectThe past 30 years have seen a shift in the timing of surgery for aneurysmal subarachnoid hemorrhage (SAH). Earlier practices of delayed surgery that were intended to avoid less favorable surgical conditions have been replaced by a trend toward early surgery to minimize the risks associated with rebleeding and vasospasm. Yet, a consensus as to the optimal timing of surgery has not been reached. The authors hypothesized that earlier surgery, performed using contemporary neurosurgical and neuroanesthesia techniques, would be associated with better outcomes when using contemporary management practices, and sought to define the optimal time interval between SAH and surgery.MethodsData collected as part of the Intraoperative Hypothermia for Aneurysm Surgery Trial (IHAST) were analyzed to investigate the relationship between timing of surgery and outcome at 3 months post-SAH. The IHAST enrolled 1001 patients in 30 neurosurgical centers between February 2000 and April 2003. All patients had a radiographically confirmed SAH, were World Federation of Neurosurgical Societies Grades I–III at the time of surgery, and underwent surgical clipping of the presumed culprit aneurysm within 14 days of the date of hemorrhage. Patients were seen at 90-day follow-up visits. The primary outcome variable was a Glasgow Outcome Scale score of 1 (good outcome). Intergroup differences in baseline, intraoperative, and postoperative variables were compared using the Fisher exact tests. Variables reported as means were compared with ANOVA. Multiple logistic regression was used for multivariate analysis, adjusting for covariates. A p value of less than 0.05 was considered to be significant.ResultsPatients who underwent surgery on Days 1 or 2 (early) or Days 7–14 (late) (Day 0 = date of SAH) fared better than patients who underwent surgery on Days 3–6 (intermediate). Specifically, the worst outcomes were observed in patients who underwent surgery on Days 3 and 4. Patients who had hydrocephalus or Fisher Grade 3 or 4 on admission head CT scans had better outcomes with early surgery than with intermediate or late surgery.ConclusionsEarly surgery, in good-grade patients within 48 hours of SAH, is associated with better outcomes than surgery performed in the 3- to 6-day posthemorrhage interval. Surgical treatment for aneurysmal SAH may be more hazardous during the 3- to 6-day interval, but this should be weighed against the risk of rebleeding.

scholarly journals Evaluation of COVID-19 vaccination strategies with a delayed second dose

PLoS Biology ◽  
2021 ◽  
Vol 19 (4) ◽  
pp. e3001211
Author(s):  
Seyed M. Moghadas ◽  
Thomas N. Vilches ◽  
Kevin Zhang ◽  
Shokoofeh Nourbakhsh ◽  
Pratha Sah ◽  
...  
Keyword(s):  
Program Effectiveness ◽  
Credible Interval ◽  
The United States ◽  
Optimal Time ◽  
Time Interval ◽  
Policy Debate ◽  
Agent Based ◽  
Vaccination Strategies ◽  
Supply And Distribution ◽  
The Impact

Two of the Coronavirus Disease 2019 (COVID-19) vaccines currently approved in the United States require 2 doses, administered 3 to 4 weeks apart. Constraints in vaccine supply and distribution capacity, together with a deadly wave of COVID-19 from November 2020 to January 2021 and the emergence of highly contagious Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants, sparked a policy debate on whether to vaccinate more individuals with the first dose of available vaccines and delay the second dose or to continue with the recommended 2-dose series as tested in clinical trials. We developed an agent-based model of COVID-19 transmission to compare the impact of these 2 vaccination strategies, while varying the temporal waning of vaccine efficacy following the first dose and the level of preexisting immunity in the population. Our results show that for Moderna vaccines, a delay of at least 9 weeks could maximize vaccination program effectiveness and avert at least an additional 17.3 (95% credible interval [CrI]: 7.8–29.7) infections, 0.69 (95% CrI: 0.52–0.97) hospitalizations, and 0.34 (95% CrI: 0.25–0.44) deaths per 10,000 population compared to the recommended 4-week interval between the 2 doses. Pfizer-BioNTech vaccines also averted an additional 0.60 (95% CrI: 0.37–0.89) hospitalizations and 0.32 (95% CrI: 0.23–0.45) deaths per 10,000 population in a 9-week delayed second dose (DSD) strategy compared to the 3-week recommended schedule between doses. However, there was no clear advantage of delaying the second dose with Pfizer-BioNTech vaccines in reducing infections, unless the efficacy of the first dose did not wane over time. Our findings underscore the importance of quantifying the characteristics and durability of vaccine-induced protection after the first dose in order to determine the optimal time interval between the 2 doses.

scholarly journals The Interval Between Staged Bilateral Total Knee Arthroplasties Does Not Affect Early Complications of the Second Knee or Long-term Function of the First and Second Knees

2021 ◽  
Author(s):  
Guangqian Shang ◽  
Shuai Xiang ◽  
Jianjun Guo ◽  
Feng Ji ◽  
Shuai Yang ◽  
...  
Keyword(s):  
Complication Rate ◽  
Optimal Time ◽  
Time Interval ◽  
Early Complications ◽  
Postoperative Function ◽  
Term Function ◽  
Significant Difference ◽  
Patient Reported ◽  
Total Knee

Abstract Background: This study explored the optimal time interval between staged bilateral total knee arthroplasty (BTKA) to minimise early complications of the second TKA and maximise long-term function of the first and second knees.Methods: We retrospectively reviewed 266 patients who underwent staged BTKA between 2010 and 2015. Groups 1–4 had time intervals between BTKAs of 1–6, 6–12, 12–18, and 18–24 months, respectively. Demographics, postoperative complications within 90 days of the second TKA, Knee Society Score (KSS), and Western Ontario and McMaster Universities Arthritis Index (WOMAC) score were compared among the groups.Results: In total, 54, 96, 75, and 41 patients were assigned to groups 1–4, respectively. Although group 1 had the highest overall complication rate (11.11%), there was no significant difference in the complication rate among the four groups. Also, no significant differences were found among the four groups in functional and patient-reported outcomes, in either the first or second knee at 5 years postoperatively, including KSS-knee, KSS-function, WOMAC-pain, WOMAC-stiffness, and WOMAC-physical function. The interval between BTKA did not influence complications or the function of the second knee. The TKA type (posterior-stabilised vs. medial-pivot) and age did not correlate significantly with any scores.Conclusions: There was no group difference in early complications of the second TKA, and postoperative function was equivalent between the two knees and did not vary by the interval between surgeries. Our results can help surgeons discuss the timing of the second TKA with patients, which should be based on their own preferences. If patients cannot tolerate severe symptoms in the contralateral knee after the first TKA, the second TKA should be performed as early as possible.

A Preventive Action Management Platform in Healthcare Information Systems

2013 ◽  
Vol 2 (3) ◽  
pp. 16-29 ◽  
Author(s):  
Hugo Peixoto ◽  
António Abelha ◽  
Manuel Santos ◽  
José Machado
Keyword(s):  
Optimal Time ◽  
Time Interval ◽  
Administrative Staff ◽  
Preventive Action ◽  
End User ◽  
Estimation Model ◽  
Web Based ◽  
Healthcare Information Systems ◽  
Management Platform ◽  
Preventive Actions

Preventive actions management plays a crucial role in clinical applications, not only for those who depend on data to make decisions, but also for those who monitor the operational and financial impact of the systems. This paper presents an open-source platform, named ScheduleIT, capable of managing preventive routines. The platform is based on an estimation model that determines the optimal time interval for interventions, according to the criticality of the system and the number of non-programmed faults, among others. ScheduleIT has a web-based interface available to a different area end-user, ranging from IT technicians to administrative staff. At this point, the platform covers around 75% of the healthcare systems and it is fully accepted by its main users as a reliable and effective preventive tool.

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