Qingqing Zhai

National University of Singapore, Industrial & Systems Engineering, Post-Doc

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Qingqing Zhai is currently a Lecturer in Shanghai Univeristy, School of Management. His research interests include degradation modeling and complex systems reliability modeling.

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Remo Caponi

University of Cologne

Farouq Alam

King AbdulAziz University (KAU) Jeddah, Saudi Arabia

Sergei Ostroumov

Moscow State University

Felipe Torres

Pontificia Universidad Catolica de Chile

Craig Tovey

Georgia Institute of Technology

Sunoj SM

Cochin University of Science and Technology

G. Iovine

Consiglio Nazionale delle Ricerche (CNR)

Luc Gwiazdzinski

Université Toulouse II Jean Jaurès

Marco V. Boniardi

Politecnico di Milano

Roland T Loto

Covenant University Canaanland, Ota.

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Papers by Qingqing Zhai

Optimal Working Sequence in a 1-Out-Of-N Warm Standby System

Reliability Modelling and Optimization of Warm Standby Systems

$Research paper thumbnail of Reliability of $${\varvec{k}}$$-Out-Of-$${\varvec{n}}$$ Warm Standby Systems$

Reliability of $${\varvec{k}}$$-Out-Of-$${\varvec{n}}$$ Warm Standby Systems

In real-life applications, the operation of systems requires the simultaneous work of multiple units

Reliability of Warm Standby Systems with Complex Structure

The redundant systems with warm standby components studied in the previous chapters are all simpl... more

Reliability of 1-out-of-(n+1) Warm Standby Systems Subject to Fault Level Coverage

International journal of performability engineering, 2013

Warm standby SParing (WSP) is a commonly-used fault tolerance technique that compromises the syst... more Warm standby SParing (WSP) is a commonly-used fault tolerance technique that compromises the system energy consumption and recovery time. Imperfect fault coverage is an important factor that can restrict the reliability of a fault-tolerant system. In this paper, a generalized binary decision diagram (BDD)-based approach is presented to evaluate the reliability of a 1-out-of-(n+1) warm standby system subject to fault level coverage. Examples are presented to illustrate the application of the proposed method.

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Cox Survival Model based Optimal Screening Strategy for Tuberculosis

2019 Prognostics and System Health Management Conference (PHM-Qingdao), 2019

Tuberculosis is one of leading threats to human beings’ health. Thus, the screening is essential ... more Tuberculosis is one of leading threats to human beings’ health. Thus, the screening is essential as it can contribute to the more effective treatment of the patients infected with tuberculosis and the reduction of unintended infection from these patients to others. Adopting the Cox survival model to characterize the infection probability, an optimal screening strategy is proposed to minimize the corresponding total cost. Numerical examples are presented to illustrate the proposed model.

Optimal Attack Strategy to a Network Consisting of Interdependent Subnetworks

This paper analyzes the optimal strategies for the attacker in an attack-defense game on a networ... more This paper analyzes the optimal strategies for the attacker in an attack-defense game on a network consisting of interdependent subnetworks. The defender moves first and evenly allocates the scarce resource to protect the network nodes. The attacker moves after observing the actions taken by the defender, allocating its limited resources to attack the network nodes. Binary Decision Diagram is employed to obtain all potential states of a given interdependent network after attack. For each of the defender's given strategies, the attacker tries to maximize its cumulative prospect value considering all possible outcomes. Illustrative example is solved to show the applications

Optimal Abort Policy of a Distributed System of Computers with Weibull Failure Time

This study tries to design a task abort policy for distributed computing systems in order to enha... more This study tries to design a task abort policy for distributed computing systems in order to enhance its mission completion probability. Particularly, a task may need to be aborted when it cannot be completed at a time threshold. This study assumes that the time of each computer spent on executing its task on follows Weibull distribution. Some additional rules are introduced from the aspect of practical application. Based on an approach of multi-valued decision diagram, a system reliability is evaluated considering the abort policy.

Risk Factors of Psychological Responses of Chinese University Students During the COVID-19 Outbreak: Cross-sectional Web-Based Survey Study

Background COVID-19 is a highly contagious and highly pathogenic disease caused by a novel corona... more Background COVID-19 is a highly contagious and highly pathogenic disease caused by a novel coronavirus, SARS-CoV-2, and it has become a pandemic. As a vulnerable population, university students are at high risk during the epidemic, as they have high mobility and often overlook the severity of the disease because they receive incomplete information about the epidemic. In addition to the risk of death from infection, the epidemic has placed substantial psychological pressure on the public. In this respect, university students are more prone to psychological problems induced by the epidemic compared to the general population because for most students, university life is their first time outside the structure of the family, and their mental development is still immature. Internal and external expectations and academic stress lead to excessive pressure on students, and unhealthy lifestyles also deteriorate their mental health. The outbreak of COVID-19 was a significant social event, and ...

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Reliability of Warm Standby Systems with Phased-Mission Requirement

In the preceding chapters, we analyze the system reliability under fixed system demand. In realit... more

From the reliability modeling perspective, the warm standby component can fail both in the warm s... more

Analysis of time-censored aggregate data

2017 Second International Conference on Reliability Systems Engineering (ICRSE), 2017

For complex systems with many components, it is a heavy burden to accurately record all the failu... more For complex systems with many components, it is a heavy burden to accurately record all the failure times of each component. To ease the information storage, practitioners in industry may only record the number of failures during an operation interval instead. Such a type of data compresses the detailed failure information and may be called time-censored aggregate data. Because only limited information is available, the statistical inference for aggregate data is more challenging than traditional lifetime data. This study focuses on the statistical analysis of time-censored aggregate data, and four popular parametric lifetime distributions are used to model such data. We first use the gamma distribution and the inverse Gaussian (IG) distribution to model the data, and exploit the maximum likelihood (ML) method for parameter estimation. Then, we fit the data by the Weibull distribution and the log-normal distribution. Unlike the gamma and IG distributions, the Weibull and the log-nor...

Resilience Analysis of Multistate Systems Based on Markov Reward Processes

2019 4th International Conference on System Reliability and Safety (ICSRS)

In this paper, we develop a resilience modelling and analysis framework for multistate systems. T... more In this paper, we develop a resilience modelling and analysis framework for multistate systems. The developed framework is based on Markov reward processes, in which the performance degradation and recovery processes of the multistate system are modeled by a continuous time discrete state Markov chain, and the losses caused by disruptive events are modeled by reward rates. A numerical metric is defined to quantify resilience based on the losses the system suffered from the disruptive events. The developed methods are applied to analyze the resilience of a nuclear power plant under the threat of earthquakes.

Optimal Course of Statins for Patients With Aneurysmal Subarachnoid Hemorrhage: Is Longer Treatment Better? A Meta-Analysis of Randomized Controlled Trials

Frontiers in Neuroscience

Statins are used in clinical practice to prevent from complications such as cerebral vasospasm (C... more Statins are used in clinical practice to prevent from complications such as cerebral vasospasm (CVS) after aneurysmal subarachnoid hemorrhage (aSAH). However, the efficacy and safety of statins are still controversial due to insufficient evidence from randomized controlled trials and inconsistent results of the existing studies. This meta-analysis aimed to systematically review the latest evidence on the time window and complications of statins in aSAH. The randomized controlled trials in the databases of The Cochrane Library, PubMed, Web of Science, Embase, CNKI, and Wanfang from January 2005 to April 2021 were searched and analyzed systematically. Data analysis was performed using Stata version 16.0. The fixed-effects model (M-H method) with effect size risk ratio (RR) was used for subgroups with homogeneity, and the random-effects model (D-L method) with effect size odds ratio (OR) was used for subgroups with heterogeneity. The primary outcomes were poor neurological prognosis an...

Degradation modeling considering unit-to-unit heterogeneity-A general model and comparative study

Reliability Engineering & System Safety

A Markov reward process-based framework for resilience analysis of multistate energy systems under the threat of extreme events

Reliability Engineering & System Safety

The Application of Seamless Nursing to Patients with Nephrotic Syndrome

American Journal of Nursing Science

Objective: To assess the application of seamless nursing to patients with nephrotic syndrome. Met... more Objective: To assess the application of seamless nursing to patients with nephrotic syndrome. Methods: 88 nephrotic syndrome patients agree to join our study, they were diagnosed as nephrotic syndrome in the hospital from May 2018 to October 2019. The participants were randomly assigned the participants to two groups, that include control group (n = 44) and intervention group (n = 44). We provide conventional nursing service to the control group participants in the treatment process. Also, intervention group participants receive seamless nursing services. Our researchers collected anxiety information and depression information by questionnaires which include Self-Rating Anxiety Scale (SAS) and Self-rating depression scale (SDS). In addition, we collect the information was associated with participants characteristics from hospital database and participant satisfaction of satisfaction questionnaire. Result: In depression-and anxiety-research result, the two groups have similar assessment result in SAS and SDS of before the nursing, they are not statistical significance. However, the result of after the nursing is different in SDS and SAS. The intervention group participants have better performance in SAS and SDS result (34.21±1.26 vs 44.21±3.83, 32.37±2.81 vs 46.51±5.7). In patient satisfaction research, all participants have good satisfaction assessment for nursing service (95.5% & 77.3%). But intervention group has obviously improvement in our research result. In intervention group assessment, most assessment are very well (n = 24). Conclusion: The seamless nursing has strongly improvement to depression and anxiety of patient, and patient satisfaction.

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Optimal design of facility allocation and maintenance strategy for a cellular network

Reliability Engineering & System Safety

How reliable should military UAVs be?

IISE Transactions

Abstract The recent decade has witnessed an emerging usage of Unmanned Aerial Vehicles (UAVs) in ... more Abstract The recent decade has witnessed an emerging usage of Unmanned Aerial Vehicles (UAVs) in both military and civilian applications. Compared with manned aircraft, a much larger percentage of UAVs are reported to crash every year, due to its unmanned nature and immature technologies. The high failure rate is mainly attributed to the lack of redundancy design and insufficient reliability growth tests. It is natural to ask whether the UAVs are reliable enough, and to what extent we shall improve the reliability of the UAVs. Through cost modeling, this study shows that the designed reliability for military UAVs needs not be extremely high. The main reason is that military UAVs are exposed to external threats such as enemy fire and cyber-attacks. Reliability enhancement actions are able to improve the operational reliability, but cannot ease the external threats to the UAVs. In our UAV cost models, both the reliability enhancement actions using reliability growth test and external failures due to intentional attacks are considered, based on which the optimal reliability growth duration that minimizes the total operation cost is derived. We investigate the impacts of the reliability growth pattern and the intensity of external threats on the effectiveness of the reliability growth test. Particularly, the external threats can weaken the effectiveness of the reliability growth test in terms of the overall operation cost. An illustrative example is used to demonstrate our model and support our results.

Defender–Attacker Games with Asymmetric Player Utilities

Risk Analysis

The presence of strategic attackers has become an important factor in the security and protection... more The presence of strategic attackers has become an important factor in the security and protection of systems, especially since the 9/11/2001 attacks, and considerable efforts have been dedicated to its study. When defending against the strategic attacker, many existing studies assume that the attacker would seek to minimize the defender's utility, which implies that the defender and attacker have symmetric utilities. However, the attacker's objective is determined by its own valuation of the system and target of the attack, which is not necessarily consistent with the defender's utility. If the attacker unexpectedly targets a different utility, then the defense strategy might no longer be optimal. In particular, the defense strategy could be inferior if the attacker's utility is not known to the defender. This study considers a situation where the defender's utility is the system survivability and the attacker's utility is the expected number of destroyed elements in the system. We investigate possible attack strategies under these two different utilities and compare (a) the conservative defense strategy when the attack utility is unknown to the defender with (b) the optimal defense strategy when the attack utility is known to the defender. We show that the conservative protection strategy is still optimal under asymmetric utilities when the contest intensity is smaller than one.

Modeling Changes to Survey Response Items Over Time in a Britain Financial Literacy Education Study

Journal of Financial Counseling and Planning

This study develops a general method for modeling changes in response to items relating to studen... more This study develops a general method for modeling changes in response to items relating to students perceptions of personal finance and financial products. The new method is illustrated to analyze data from a sample of 1,250 students aged 16–18 who participated in a financial capability education study in the UK. We demonstrate how a quantitative indicator of the changes in students' responses can be applied in various educational research projects, particularly as a measure of program effectiveness. Predictions are based on prior survey responses, which are taken as relevant historical information for a cohort of students. We find significant changes in the responses of students toward reported career choice following the Financial Literacy Education course at national colleges in the UK.

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Optimal Working Sequence in a 1-Out-Of-N Warm Standby System

Reliability Modelling and Optimization of Warm Standby Systems

$Research paper thumbnail of Reliability of $${\varvec{k}}$$-Out-Of-$${\varvec{n}}$$ Warm Standby Systems$

Reliability of $${\varvec{k}}$$-Out-Of-$${\varvec{n}}$$ Warm Standby Systems

In real-life applications, the operation of systems requires the simultaneous work of multiple units

Reliability of Warm Standby Systems with Complex Structure

The redundant systems with warm standby components studied in the previous chapters are all simpl... more

Reliability of 1-out-of-(n+1) Warm Standby Systems Subject to Fault Level Coverage

International journal of performability engineering, 2013

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Cox Survival Model based Optimal Screening Strategy for Tuberculosis