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Suprasad Amari

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Papers by Suprasad Amari

Reliability Evaluation of Standby Systems

Fundamentals of Binary Decision Diagrams

Reliability Analysis of Fault Tolerant Systems with Multi-Fault Coverage

International journal of performability engineering, Oct 1, 2007

Fault-tolerance has been an essential architectural attribute for achieving high reliability in m... more Fault-tolerance has been an essential architectural attribute for achieving high reliability in many critical applications of digital systems. Automatic fault and error handling mechanisms play a crucial role in implementing fault tolerance because an uncovered (undetected) fault may lead to a system or a subsystem failure even when adequate redundancy exists. Examples of this effect can be found in computing systems, electrical power distribution networks, pipelines carrying dangerous materials etc. Because an uncovered fault may lead to overall system failure, an excessive level of redundancy may even reduce the system reliability. Therefore, an accurate analysis must account for not only the system structure, but also the system fault & error handling behavior (often called coverage behavior) as well. The appropriate coverage modeling approach depends on the type of fault tolerant techniques used. The recent research literature emphasizes the importance of multi-fault coverage models where the effectiveness of recovery mechanisms depends on the coexistence of multiple faults in a group of elements, which are also called fault level coverage (FLC) groups, that collectively participate in detecting and recovering the faults in that group. However, the methods for solving multi-fault coverage models are limited, primarily because of the complex nature of the dependency introduced by the reconfiguration mechanisms. The paper suggests a modification of the generalized reliability block diagram (RBD) method for evaluating reliability indices of systems with multi-fault coverage. The suggested method based on a universal generating function technique computes the reliability indices of complex systems with multi-fault coverage using a straightforward recursive procedure. The proposed algorithm can be easily used in the case of hierarchical structure of FLC groups. Illustrative examples are presented.

Shared Decision Diagrams

Efficient reliability analysis of dynamic k-out-of-n heterogeneous phased-mission systems

Reliability Engineering & System Safety, 2020

Abstract In this paper, an efficient analytical modeling method is proposed for reliability analy... more Abstract In this paper, an efficient analytical modeling method is proposed for reliability analysis of k-out-of-n phased-mission systems (PMSs). A PMS is a system involving multiple, consecutive and non-overlapping phases of tasks during its mission, which abounds in complex technological systems such as aerospace systems, nuclear power plants, and high-performance computing systems. Due to dynamics in the system configuration and component behavior as well as statistical dependences across phases, exact reliability evaluation of a PMS is a time-consuming and complicated task. This paper proposes a new efficient multi-valued decision diagram (MDD) based method for the reliability analysis of a special class of non-repairable PMSs called k-out-of-n PMS where the same number of components n is involved in all the phases but the required number of working components k may vary from phase to phase. Particularly, a new MDD generation method is proposed for a fast construction of the PMS MDD model. The system components are not necessarily identical; they can be heterogeneous in their failure time distributions. Examples are provided to demonstrate the application and advantages of the proposed methodology.

Reliability aspects of a series load–sharing system

CRC Press eBooks, Jun 15, 2018

In reliability engineering, load-sharing is typically associated with a system in parallel config... more In reliability engineering, load-sharing is typically associated with a system in parallel configuration. Examples include bridge support structures, electric power supply systems, multiprocessor computing systems, etc. We consider a reliability maximization problem for a high-voltage commutation device, wherein the total voltage across the device is shared by the components in series configuration. Here, the increase of the number of load-sharing components increases component-level reliability (as the voltage load per component reduces) but may decrease system-level reliability (due to the increased number of components in series). We review optimal solutions for the proportional hazard and accelerated life models with the underlying exponential & Weibull distributions and elaborate on the log-linear, power, and Eyring laws used in the life-load models.

Basic Reliability Theory and Models

Phased-Mission Systems

Reliability of Nonrepairable Phased-Mission Systems With Common Cause Failures

IEEE transactions on systems, man, and cybernetics, Jun 1, 2013

In this paper, we propose a recursive and exact method for reliability evaluation of phased-missi... more In this paper, we propose a recursive and exact method for reliability evaluation of phased-mission systems with failures originating from some system elements that can propagate causing the common cause failures of groups of elements. The system consists of multiple, consecutive, non-overlapping phases of operation, and non-identical binary non-repairable elements that can fail individually or due to propagated failures originating from other elements. The overall system can have binary states corresponding to the mission success and failure or multiple states characterized by different levels of system performance. Based on conditional probabilities as well as the branch and bound principle, the proposed method takes into account dynamic changes in system structure and demand across different phases. It also considers time-varying, phase-dependent failure rates and associated cumulative damage effects for the system elements. The main advantage of this method is that it does not require composition of decision diagrams and can be fully automated. Both an analytical example and a numerical example are analyzed to illustrate the proposed method.

Optimal Design of&lt;tex&gt;$k$&lt;/tex&gt;-out-of-&lt;tex&gt;$n$&lt;/tex&gt;:G Subsystems Subjected to Imperfect Fault-Coverage

IEEE Transactions on Reliability, Dec 1, 2004

An efficient phased-mission reliability model considering dynamic k-out-of-n subsystem redundancy

IISE Transactions, 2018

Prior to joining BAE Systems, Dr. Amari served about 14 years as a Technical Fellow at Parametric... more Prior to joining BAE Systems, Dr. Amari served about 14 years as a Technical Fellow at Parametric Technology Corporation (PTC) where he led the design and development of advanced modeling features and computational algorithms for Windchill Quality Solutions (formerly Relex) Software Product Suite. He also worked at Relyence Corporation as a product manager and reliability subject matter expert. From 1996 to 2001, Dr. Amari worked at Tata Consultancy Services (TCS) where he served as technical lead of the Data Mining and Machine Learning group. His research interests include hardware and software reliability, fault-tolerant computing, dynamic dependability models, and condition-based maintenance. He has authored or coauthored 6 book chapters in Springer Handbooks and over 80 research papers published in reputable international journals and conference proceedings. He coauthored a book with Dr. Liudong Xing on Binary Decision Diagrams and Extensions for System Reliability Analysis. He is Co-Editor-in-Chief for the International Journal of Performability Engineering (IJPE) and an editorial board

Fault Tolerant Systems and Coverage Models

Xing/Binary, 2015

Reliability Characteristics and Optimization of Warm Standby Systems

Springer eBooks, 2023

RAMS 2014 Author Index

RAMS 2012-Securing Tomorrow's Future with Reliability and Maintainability

Chen Gaung-Cheng, see Yeh, RH, TR Mar 05 92-97

2014 Index IEEE Transactions on Reliability Vol. 63

IEEE Transactions on Reliability, 2014

This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this... more This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during 2014, and items from previous years that were commented upon or corrected in 2014. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

2013 Index IEEE Transactions on Systems, Man, and Cybernetics: Systems Vol. 43

IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2013

This index covers all technical items papers, correspondence, reviews, etc. that appeared in this... more This index covers all technical items papers, correspondence, reviews, etc. that appeared in this periodical during 2013, and items from previous years that were commented upon or corrected in 2013. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

Reliability analysis of fault-tolerant systems with common-cause failures

2003 International Conference on Dependable Systems and Networks, 2003. Proceedings.

Fault-tolerance has been an essential architectural attribute for achieving high reliability in m... more Fault-tolerance has been an essential architectural attribute for achieving high reliability in many critical applications of digital systems. Automatic fault and error handling mechanisms play a crucial role in implementing fault tolerance because an uncovered (undetected) fault may lead to a system or a subsystem failure even when adequate redundancy exists. Examples of this effect can be found in computing systems, electrical power distribution networks, pipelines carrying dangerous materials etc. Because an uncovered fault may lead to overall system failure, an excessive level of redundancy may even reduce the system reliability. Therefore, an accurate analysis must account for not only the system structure, but also the system fault & error handling behavior (often called coverage behavior) as well. The appropriate coverage modeling approach depends on the type of fault tolerant techniques used. The recent research literature emphasizes the importance of multi-fault coverage models where the effectiveness of recovery mechanisms depends on the coexistence of multiple faults in a group of elements, which are also called fault level coverage (FLC) groups, that collectively participate in detecting and recovering the faults in that group. However, the methods for solving multi-fault coverage models are limited, primarily because of the complex nature of the dependency introduced by the reconfiguration mechanisms. The paper suggests a modification of the generalized reliability block diagram (RBD) method for evaluating reliability indices of systems with multi-fault coverage. The suggested method based on a universal generating function technique computes the reliability indices of complex systems with multi-fault coverage using a straightforward recursive procedure. The proposed algorithm can be easily used in the case of hierarchical structure of FLC groups. Illustrative examples are presented.

A Novel Approach for Optimal Cost-Effective Design of Complex Repairable Systems

IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans, 2007

Abstract Almost every engineering and manufacturing system consists of several subsystems, which ... more

Reliability Evaluation of Standby Systems

Fundamentals of Binary Decision Diagrams

Reliability Analysis of Fault Tolerant Systems with Multi-Fault Coverage

International journal of performability engineering, Oct 1, 2007

Fault-tolerance has been an essential architectural attribute for achieving high reliability in m... more Fault-tolerance has been an essential architectural attribute for achieving high reliability in many critical applications of digital systems. Automatic fault and error handling mechanisms play a crucial role in implementing fault tolerance because an uncovered (undetected) fault may lead to a system or a subsystem failure even when adequate redundancy exists. Examples of this effect can be found in computing systems, electrical power distribution networks, pipelines carrying dangerous materials etc. Because an uncovered fault may lead to overall system failure, an excessive level of redundancy may even reduce the system reliability. Therefore, an accurate analysis must account for not only the system structure, but also the system fault & error handling behavior (often called coverage behavior) as well. The appropriate coverage modeling approach depends on the type of fault tolerant techniques used. The recent research literature emphasizes the importance of multi-fault coverage models where the effectiveness of recovery mechanisms depends on the coexistence of multiple faults in a group of elements, which are also called fault level coverage (FLC) groups, that collectively participate in detecting and recovering the faults in that group. However, the methods for solving multi-fault coverage models are limited, primarily because of the complex nature of the dependency introduced by the reconfiguration mechanisms. The paper suggests a modification of the generalized reliability block diagram (RBD) method for evaluating reliability indices of systems with multi-fault coverage. The suggested method based on a universal generating function technique computes the reliability indices of complex systems with multi-fault coverage using a straightforward recursive procedure. The proposed algorithm can be easily used in the case of hierarchical structure of FLC groups. Illustrative examples are presented.

Shared Decision Diagrams

Efficient reliability analysis of dynamic k-out-of-n heterogeneous phased-mission systems

Reliability Engineering & System Safety, 2020

Abstract In this paper, an efficient analytical modeling method is proposed for reliability analy... more Abstract In this paper, an efficient analytical modeling method is proposed for reliability analysis of k-out-of-n phased-mission systems (PMSs). A PMS is a system involving multiple, consecutive and non-overlapping phases of tasks during its mission, which abounds in complex technological systems such as aerospace systems, nuclear power plants, and high-performance computing systems. Due to dynamics in the system configuration and component behavior as well as statistical dependences across phases, exact reliability evaluation of a PMS is a time-consuming and complicated task. This paper proposes a new efficient multi-valued decision diagram (MDD) based method for the reliability analysis of a special class of non-repairable PMSs called k-out-of-n PMS where the same number of components n is involved in all the phases but the required number of working components k may vary from phase to phase. Particularly, a new MDD generation method is proposed for a fast construction of the PMS MDD model. The system components are not necessarily identical; they can be heterogeneous in their failure time distributions. Examples are provided to demonstrate the application and advantages of the proposed methodology.

Reliability aspects of a series load–sharing system

CRC Press eBooks, Jun 15, 2018

In reliability engineering, load-sharing is typically associated with a system in parallel config... more In reliability engineering, load-sharing is typically associated with a system in parallel configuration. Examples include bridge support structures, electric power supply systems, multiprocessor computing systems, etc. We consider a reliability maximization problem for a high-voltage commutation device, wherein the total voltage across the device is shared by the components in series configuration. Here, the increase of the number of load-sharing components increases component-level reliability (as the voltage load per component reduces) but may decrease system-level reliability (due to the increased number of components in series). We review optimal solutions for the proportional hazard and accelerated life models with the underlying exponential & Weibull distributions and elaborate on the log-linear, power, and Eyring laws used in the life-load models.

Basic Reliability Theory and Models

Phased-Mission Systems

Reliability of Nonrepairable Phased-Mission Systems With Common Cause Failures

IEEE transactions on systems, man, and cybernetics, Jun 1, 2013

In this paper, we propose a recursive and exact method for reliability evaluation of phased-missi... more In this paper, we propose a recursive and exact method for reliability evaluation of phased-mission systems with failures originating from some system elements that can propagate causing the common cause failures of groups of elements. The system consists of multiple, consecutive, non-overlapping phases of operation, and non-identical binary non-repairable elements that can fail individually or due to propagated failures originating from other elements. The overall system can have binary states corresponding to the mission success and failure or multiple states characterized by different levels of system performance. Based on conditional probabilities as well as the branch and bound principle, the proposed method takes into account dynamic changes in system structure and demand across different phases. It also considers time-varying, phase-dependent failure rates and associated cumulative damage effects for the system elements. The main advantage of this method is that it does not require composition of decision diagrams and can be fully automated. Both an analytical example and a numerical example are analyzed to illustrate the proposed method.

Optimal Design of&lt;tex&gt;$k$&lt;/tex&gt;-out-of-&lt;tex&gt;$n$&lt;/tex&gt;:G Subsystems Subjected to Imperfect Fault-Coverage

IEEE Transactions on Reliability, Dec 1, 2004

An efficient phased-mission reliability model considering dynamic k-out-of-n subsystem redundancy

IISE Transactions, 2018

Prior to joining BAE Systems, Dr. Amari served about 14 years as a Technical Fellow at Parametric... more Prior to joining BAE Systems, Dr. Amari served about 14 years as a Technical Fellow at Parametric Technology Corporation (PTC) where he led the design and development of advanced modeling features and computational algorithms for Windchill Quality Solutions (formerly Relex) Software Product Suite. He also worked at Relyence Corporation as a product manager and reliability subject matter expert. From 1996 to 2001, Dr. Amari worked at Tata Consultancy Services (TCS) where he served as technical lead of the Data Mining and Machine Learning group. His research interests include hardware and software reliability, fault-tolerant computing, dynamic dependability models, and condition-based maintenance. He has authored or coauthored 6 book chapters in Springer Handbooks and over 80 research papers published in reputable international journals and conference proceedings. He coauthored a book with Dr. Liudong Xing on Binary Decision Diagrams and Extensions for System Reliability Analysis. He is Co-Editor-in-Chief for the International Journal of Performability Engineering (IJPE) and an editorial board

Fault Tolerant Systems and Coverage Models

Xing/Binary, 2015

Reliability Characteristics and Optimization of Warm Standby Systems

Springer eBooks, 2023

RAMS 2014 Author Index

RAMS 2012-Securing Tomorrow's Future with Reliability and Maintainability

Chen Gaung-Cheng, see Yeh, RH, TR Mar 05 92-97

2014 Index IEEE Transactions on Reliability Vol. 63

IEEE Transactions on Reliability, 2014

This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this... more This index covers all technical items-papers, correspondence, reviews, etc.-that appeared in this periodical during 2014, and items from previous years that were commented upon or corrected in 2014. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

2013 Index IEEE Transactions on Systems, Man, and Cybernetics: Systems Vol. 43

IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2013

This index covers all technical items papers, correspondence, reviews, etc. that appeared in this... more This index covers all technical items papers, correspondence, reviews, etc. that appeared in this periodical during 2013, and items from previous years that were commented upon or corrected in 2013. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author's name. The primary entry includes the coauthors' names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author's name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index.

Reliability analysis of fault-tolerant systems with common-cause failures

2003 International Conference on Dependable Systems and Networks, 2003. Proceedings.

Fault-tolerance has been an essential architectural attribute for achieving high reliability in m... more Fault-tolerance has been an essential architectural attribute for achieving high reliability in many critical applications of digital systems. Automatic fault and error handling mechanisms play a crucial role in implementing fault tolerance because an uncovered (undetected) fault may lead to a system or a subsystem failure even when adequate redundancy exists. Examples of this effect can be found in computing systems, electrical power distribution networks, pipelines carrying dangerous materials etc. Because an uncovered fault may lead to overall system failure, an excessive level of redundancy may even reduce the system reliability. Therefore, an accurate analysis must account for not only the system structure, but also the system fault & error handling behavior (often called coverage behavior) as well. The appropriate coverage modeling approach depends on the type of fault tolerant techniques used. The recent research literature emphasizes the importance of multi-fault coverage models where the effectiveness of recovery mechanisms depends on the coexistence of multiple faults in a group of elements, which are also called fault level coverage (FLC) groups, that collectively participate in detecting and recovering the faults in that group. However, the methods for solving multi-fault coverage models are limited, primarily because of the complex nature of the dependency introduced by the reconfiguration mechanisms. The paper suggests a modification of the generalized reliability block diagram (RBD) method for evaluating reliability indices of systems with multi-fault coverage. The suggested method based on a universal generating function technique computes the reliability indices of complex systems with multi-fault coverage using a straightforward recursive procedure. The proposed algorithm can be easily used in the case of hierarchical structure of FLC groups. Illustrative examples are presented.

A Novel Approach for Optimal Cost-Effective Design of Complex Repairable Systems

IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans, 2007

Abstract Almost every engineering and manufacturing system consists of several subsystems, which ... more