City infrastructure systems have distinct functions but are not isolated from one another, with interactions existing between these systems. Modeling these systems requires a focus on the system functions and interdependencies. Most models focus on system failures rather than the unexpected effects of design decisions in these systems. This paper presents a functional and spatial modeling framework suited for the representation of city infrastructure systems. This framework comprises a systematic process for breaking down the system into fundamental components and defining the relations between the system components. In addition, the spatial feature of the framework facilitates the synthesis, analysis, and evaluation of infrastructures based on their geographical locations and spatial orientations. This system modeling approach is used to design an Integrated Energy System (IES) model in order to exhibit the features of this framework. The IES consists of standard energy system estimation techniques and tools such as MATPOWER for load flow analysis, and is also used to execute a city case study. As a result, the advantages of the functional and spatial framework for modeling city infrastructures are presented. © 2013 Wiley Periodicals, Inc. Syst Eng 16:

This paper compares two common risk-modeling approaches and then uses them to analyze the risk of incorporating solar photovoltaic (PV) systems into a commercial electric power grid. It uses procedures from both approaches such as Hierarchical Holographic Models, frequency and severity normalization, and avoiding numerical skewing by rare but serious events: It describes the benefits and limitations of these approaches. Then, this paper summarizes the main risks associated with incorporating Solar PV panel systems into a commercial electric power grid, presents a what-if analysis for extreme scenarios, and explains mitigation strategies to ameliorate these risks. Finally, the paper points out some possible unintended consequences of incorporating Solar PV systems into a commercial electric power grid. © 2013 Wiley Periodicals, Inc. Syst Eng 16:

Functional architecture enables the description of systems independent of their technology. A method for obtaining functional architectures for systems (the FAS method) is introduced. It provides a well-defined procedure for deriving functional architecture from use cases by using heuristics for grouping functions and allocating them to functional blocks. A specialty of the FAS method is the structural representation of functional architectures in block-oriented form. An example system from the hearing instrument domain is used for demonstrating the method. The application of the FAS method together with the SysML modeling language is described, and modeling tool support is discussed. The authors report their experiences with the method from industrial projects, for example that analysts and architects could improve their communication by means of the FAS method. It is concluded that the method together with tool support facilitates the team process of creating model-based functional architectures based on use cases. © 2013 Wiley Periodicals, Inc. Syst Eng 17:

This paper deals with the integration process in technological systems projects. The paper reviews the objectives of the integration process, planning and managing principles, as well as the pitfalls and difficulties associated with this process. The following integration approaches are described and analyzed: hardware-assisted versus software only, bottom-up versus top-down, and hierarchial versus functional approaches. Then, a case study that focuses on the third group—the hierarchial and functional approaches—is presented. Four projects that were conducted at the same firm have been examined. The case study attempts to determine whether there is a relation between these two integration approaches and project success. The findings of the case study show that—particularly when customer satisfaction is determined as a major goal—the hierarchial integration approach is preferable to the functional approach, with respect to project success. © 2013 Wiley Periodicals, Inc. Syst Eng 17

This paper introduces a procedure to assess the credibility of models and simulations (M&S) as a group activity based on NASA’s new standard for M&S NASA-STD-7009. The Delphi method, which is characterized by iterative surveys with controlled feedback, was selected to implement the assessment. The proposed procedure is expected to address the issues in the M&S assessment related to a high level of required expertise and group decision making. An actual credibility assessment study using the proposed procedure on an M&S platform referred to as SpaceNet has been carried out by ten panel members through a two-round Delphi. The study concluded that the overall credibility of SpaceNet version 1.3 was between the development level and production level. The variances of the assessments in the second-round survey were significantly reduced compared with the first-round results, which indicates the effectiveness of the proposed procedure. © 2013 Wiley Periodicals, Inc. Syst Eng 17:

With commercial and military systems becoming more complex, using more sophisticated products, complex processes, and specialized people and having longer system life cycles, it is essential that organizations have a systematic approach to managing systems from an Obsolescence Management System perspective. This paper presents a new systems engineering architecture framework, House of Systems Engineering (HoSE), and shows how its constructs can be applied to support the building of a proactive Obsolescence Management System framework. We first provide a brief overview of the HoSE, including the systems engineering aspects and the systems architecture methodology used in the HoSE. Next, we discuss the 2-dimensional Obsolescence Management System framework based on the HoSE. Finally, a case study is performed to justify the framework. The case study results suggest that the framework is beneficial in finding gaps in an Obsolescence Management Plan. © 2013 Wiley Periodicals, Inc. Syst Eng 17

Rework that occurs late in the product life cycle is dramatically more expensive than design work performed early in the cycle. However, shifting traditional design work earlier in the design process so as to avoid rework later is difficult. A number of product development practices that have been characterized as a shift from developing a single-point design to developing a set of possible designs have proven effective at reducing development rework. This paper refines the definitions of such “set-based” development practices, which are aimed at early development phases, and shows how they can be applied to the systems engineering process in order to reduce or eliminate the root causes of rework. Examples from the Wright Brothers, Toyota, and several other companies are presented. © 2013 Wiley Periodicals, Inc. Syst Eng 17

As the integration and interoperability demands among heterogeneous systems increase, Service-Oriented Architectures (SOAs) have provided a potential technical solution to integrate these complex systems within an enterprise framework. This paper presents experimental results and future approaches to assess the employment of an SOA within a hard real-time (stringent time constraints), deterministic (maximum predictability) combat system (CS). For these systems with hard real-time requirements, web services have generally not demonstrated the necessary and sufficient characteristics to satisfy these stringent needs. Specifically, this paper provides a characterization of hard real-time, deterministic systems; results from a recent small-scale experiment to assess various SOA products in this demanding architecture; and the future direction to research real-time applications in a representative operational environment. Experimental results to date indicate that emerging real-time technologies are contributing to improved performance and better predictability within the internal processing latencies of web service applications. This preliminary research focuses on a simplistic computing architecture, but it provides a good baseline for more detailed experimentation using the actual systems. If successful, this research could lead down a path to increase synergy and consolidate computing infrastructures by supporting multiple user domains with the potential of reducing cost for both acquisition and lifecycle support. © 2013 Wiley Periodicals, Inc. Syst Eng 16

Project management is taught in most systems engineering graduate programs. Project management courses and training aids traditionally focus on aspects of project scope—for instance, scheduling and resource allocation methods—and tend to neglect product scope elements such as system performance. This article offers a simulation-based approach for project management training that integrates project and product aspects within simulation training. The result is an integrated approach that guides the trainee through the initiation, conceptual design, planning and execution phases of the simulated project. The trainee explores the tradeoffs between project and product constraints and demands—just as if he or she were working on a real job. A pilot experiment that we conducted and the trainees' evaluations of the simulation provide an initial indication that the proposed approach is efficient, motivating us to suggest a framework for its use in systems engineering programs. ©2013 Wiley Periodicals, Inc. Syst Eng 16

Systems Architecting is a decision-intensive process that stands to benefit from access to historical architectural options and the ability to rapidly generate novel ones. Despite this recognition, option generation, and, more precisely, the process of creative option generation has been underemphasized in both the decision making and system architecting literature. This paper reviews the literature on option generation from the perspective of systems architecting. It presents a framework for option generation that exploits systems thinking and psychological principles for stimulating creative option generation. It presents the system concept of an option generation aiding system that can assist systems architects in expanding and systematically exploring the option space in the early stages of architecting and design when cost avoidance is more easily achieved and change is possible. ©2013 Wiley Periodicals, Inc. Syst Eng 16

Effective and efficient risk management processes include the use of modeling and simulation during the concept exploration phase as part of the technology and risk assessment activities, with testing and evaluation tasks occurring in later design development phases. However, some safety requirements and design architectures may be dominated by the low probability/high consequence, previously unknown or uncharacterized vulnerabilities that require very early testing to characterize and efficiently mitigate. Failure to address these unique risks has led to catastrophic systems failures including the Space Shuttle Challenger, Deepwater Horizon, the Fukushima nuclear reactor, and Katrina levee failures. Discovering and addressing these risks later in the design and development process can be very costly or even lead to project cancellation. This paper presents a framework for the risk management process adoption of early hazard phenomenology testing to inform the technical risk assessment, requirements definition, and conceptual design. A case study of the lightning design vulnerability of the insensitive high explosives being used in construction, demolition, and defense industries will be presented to examine the impact of this vulnerability testing during the concept exploration phase of the design effort. ©2013 Wiley Periodicals, Inc. Syst Eng 16:

Whole system metrics are valuable tools for use in systems science and engineering. Entropy metrics are defined, developed, and demonstrated in this paper. Based on classical systems engineering methods and practices, these entropy metrics indicate the degree of order/disorder in any given system. A physical-entropy based metric and an information-based entropy metric are aligned with the two primary components of a system: objects and relationships. The physical-entropy based metric is called a relational score, and the information-based metric is called an object score. A subsystem score, based on the relational score and object score, is also developed and presented in this paper. A well-defined process, using these metrics, is used to evaluate the reduction of entropy and complexity associated with any specific system. The metrics and processes developed in this work have a prose component, a graphic component, and a mathematical component. These three components are aligned with the systems science techniques developed by John N. Warfield. ©2013 Wiley Periodicals, Inc. Syst Eng 16

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Oil companies and relevant institutions are becoming increasingly aware that effective measures must be put in place to extend the life of installations that are approaching, or have passed, the end of their design lifetime. The implementation of ageing management (AM) facilitates ensuring that the degradation of the installations is properly controlled and mitigated, and their integrity is maintained during the life extension. Integrating AM within an existing process such as maintenance management, which shares various goals and objectives with AM, seems to have several advantages over the alternative of creating a new process for AM. A key issue is to identify and optimize the changes in the maintenance management process for addressing and managing ageing. This paper reports on the use of a systems engineering approach and information models for identifying the “as is” and “to be” processes of existing maintenance management of an oil and gas facility in order to fulfill the new requirements for AM. The primary contribution of this report is to demonstrate the power of these models, combined with a systems engineering process, to reverse engineer legacy practices as the basis for introducing new processes, procedures and training. ©2013 Wiley Periodicals, Inc. Syst Eng 16:

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A data-centric, capability-focused approach is proposed to facilitate the architecture modeling and analysis of challenging system-of-systems (SoS). This approach abstracts essential information from the underlying complexity with the architecture modeling in a data-centric and semantically consistent fashion, and allows early understanding and exploration of the logical, behavioral, and performance characteristics to achieve the desired capabilities. More specifically, a high-level data meta-model, depicting the semantic relationships of constituent architectural data elements, is first presented to guide the architectural data modeling, which is aligned well with the US Department of Defense Architecture Framework (DoDAF) Meta-model (DM2). Then, the development of architectural descriptions and the construction of executable models are studied based on the core architectural data elements. Additionally, architecture analysis using static and executable models are discussed, including static analysis, dynamic analysis, and experimental analysis. The feasibility of the foregoing approach is demonstrated with an illustrative example. ©2013 Wiley Periodicals, Inc. Syst Eng 16:

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Composability is a systems architecture and design concept focusing on composing new systems from known components, designs, product lines, and reference architectures as opposed to focusing on “blank sheet” designs based on requirements decomposition alone. The concept of composability has been a goal of the US Department of Defense (DoD) for many years, most recently taking the form of Platform-based Engineering. Despite this focus, the goal of effective modularity and design reuse has been somewhat elusive in the aerospace and defense sectors. This paper describes an ecosystem construct which incorporates market factors, business practices, and trends that occur in industries where composability and reuse have taken hold in order to identify a path forward for effective adoption of composability in the aerospace and defense marketplace. A number of examples of composable design are described, followed by proposals for necessary changes within the DoD ecosystem to facilitate its support. © 2012 Wiley Periodicals, Inc. Syst Eng 16

Logistics support activities have long been part of any industrial enterprise. The increasing complexity of many systems dictated the need for outsourcing logistics support activities to specialized firms. The perceived deficiencies in many programs in the effectiveness and efficiency of that support approach motivated, a decade and a half ago, the transition to a new paradigm: instead of contracting logistics support resources as a means to achieving the desired system performance goals, customers started contracting directly the delivery of performance results. The initiative was called Performance-Based Logistics (PBL). Experience shows also that customers and contractors face a serious challenge when trying to define all the terms and conditions of a PBL contract, such as its scope, the definition of responsibilities, the metrics to be measured, the way of measuring them, the translation of measurements to rewards, and the like. This paper illustrates, based on the experience gathered by the authors, how transition contracts can play a determinant role in effectively paving the way for a migration from conventional logistics support outsourcing to performance-based logistics, reducing risks to both parties and enhancing the likelihood of their mutual satisfaction and reward. The paper captures the lessons learned in several programs and reflects them in the form of a list of issues to be validated in a transition contract, before a PBL one is entered into. © 2012 Wiley Periodicals, Inc. Syst Eng 16

We investigate potential benefits of employing the Design Structure Matrix (DSM) in the context of Model–Based Systems Engineering (MBSE) for the purposes of analyzing and improving the design of a product–project ensemble. Focusing on process DSM, we present an algorithm for a bidirectional transformation framework between a product–project system model and its corresponding Model–Based DSM (MDSM). Using Object–Process Methodology (OPM) as the underlying modeling language, we examine and characterize useful and insightful relationships between the system model and its MDSM. An unmanned aerial vehicle case study demonstrates the semantics of and analogy between various types of relationships as they are reflected in both the OPM system model and the MDSM derived from it. We conclude with further research direction on showing how clustering of DSM processes can be reflected back as an improvement of the OPM model. © 2012 Wiley Periodicals, Inc. Syst Eng 16

As exemplified in the 2010 Stuxnet attack on Iranian nuclear facilities, cyber attackers have capabilities to embed disruptive infections into equipment that is employed within physical systems. This paper presents a cyber security design approach that addresses cyber attacks that include modification of operator displays used for support in managing software controlled automated systems. This class of problems is especially important because our nation's critical infrastructures include such systems. In addition, many other systems, such as surveillance systems, navigation systems, and communications systems, are candidates for such solutions as they continue to become more and more automated. The suggested design approach builds upon fault–tolerant and automatic control system techniques that, with important and necessary modifications, are the basis for providing improved cyber security. In particular, the appropriate combination of diversely redundant security designs coupled with system dynamics models and state estimation techniques provide a potential means for detecting purposeful adjustments to operator displays. This paper provides a theoretical approach for designing such solutions and a corresponding set of examples with simulation–based results. In addition, the paper includes a discussion of important implementation requirements for greater assurance of such physical system security solutions. © 2012 Wiley Periodicals, Inc. Syst Eng 16

Conceptual design is a crucial system lifecycle stage; but systematic methods for conceptual design evaluation are not well developed, and existing approaches are not satisfactory. In this work we describe implementation and assessment of an advanced simulation environment that can serve conceptual design evaluation purposes using Object-Process Methodology (OPM). The simulation exploits two major advantages of the OPM modeling language: its integration of the structural and behavioral aspects of the system in a single type of diagram and the hierarchical organization of the model diagrams. Simulation of the system model is instrumental in understanding and exploring the behavioral aspects of the system under study and uncovering logical and conceptual problems, such as incorrect control flow, logical errors, and missing structural relations among objects. Understanding the model and correcting it are achieved via an intuitive user interface and a host of debugging capabilities, including “lifespan” and “Debug Info” components. Using these components, one can explore the state of any OPM entity and be aware of a variety of potential problems that are manifested during the simulation process. © 2012 Wiley Periodicals, Inc. Syst Eng 16

Systems engineers need quantifiable metrics for measuring the readiness of a system. The recently developed System Readiness Level (SRL) is such a metric. SRL is a function of Technology Readiness Level (TRL) and Integration Readiness Level (IRL). The mathematical operations used to define this function have some inherent properties. Four desired mathematical properties of SRL models are developed from these inherent properties and other properties suggested from a review of the literature. Matrix algebra and tropical algebra are discussed in the literature as possible mathematical operations. These mathematical operations are reviewed to determine if they meet the desired properties. Tropical Algebra (TA) is found to inherently meet these desired properties. Future research will be conducted to determine if an SRL model using TA is a viable option. ©2012 Wiley Periodicals, Inc. Syst Eng 16:

Critical considerations in engineering today's systems are securing the collection, access, and dissemination of the information they contain. Advanced computing technologies, ubiquitous environments, and sophisticated networks enable globally distributed access to data and information repositories to an uncountable community of consumers. Engineering security into these systems is more challenging and sophisticated than ever before. Along with this, assuring the integrity of highly networked systems requires economic decisions in rapidly changing technology and threat environments. Recognizing that countermeasures effective against cyber intrusions today can be ineffective tomorrow, the systems engineering community needs a rapid and agile way to identify the efficacies of competing countermeasure investment decisions. This paper presents a macroanalytic method for measuring economic-benefit returns on investments in cybersecurity. The method is called the Table Top Approach. The table top approach is designed to place light demands on the granularity of inputs to evaluate the impacts of cyber intrusion events and the benefits of countermeasure investments. The table top approach derives which investments in a set of competing choices offer the greatest cost-benefit gains in cyber defense, and why. It finds sets of Pareto efficient cost-benefit investments, and their economic returns, that capture tangible and intangible advantages of countermeasures that strengthen cybersecurity. ©2012 Wiley Periodicals, Inc. Syst Eng 16

An elementary System Oriented Event Analysis (SOEA) model was developed as an innovative method addressing serious limitations of the traditional root cause analysis (RCA) in healthcare. The SOEA has three distinctive capabilities beyond RCA: multiple events analysis, systems thinking, risk control formulation and alignment. It was applicable to events arising within strict sequential processes. However, for wider application to nonsequential, network system flows, the model needed to be redesigned. The engineering concepts of verification and validation were adopted as guides for the redesign. Patient falls in three differently sized hospitals were used to verify the applicability of the redesigned model. The resulting enriched SOEA model (enSOEA) was later applied in a scabies outbreak case as a validation test of success. This paper aims to describe how the elementary SOEA model was redesigned to achieve the enriched SOEA that is applicable beyond the sequential process, and provides key lessons learned from the tests for promoting its application. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Model-based systems engineering (MBSE) approaches are based on a paradigm shift from document-centric engineering to model-based engineering. Although MBSE methods are intended to apply across the entire system life cycle, one area that has not received much attention to date is the role of test and evaluation. Test and evaluation activities provide information that reduces the uncertainty about system performance, effectiveness, and suitability. This uncertainty reduction becomes particularly important within the context of defense systems, which can cost billions of dollars. This paper describes a methodology that uses an MBSE framework and Monte Carlo simulation to define uncertainty reduction goals for test planners to use in developing test strategies and detailed test designs for evaluating technical performance parameters. As tests are completed, physical models can be updated with test data and additional analyses conducted with combat models to determine if the system meets user requirements. The methodology is demonstrated through a simple case study involving a series of tests to predict the landing performance of an aircraft. ©2012 Wiley Periodicals, Inc. Syst Eng 16:

In September 2009 the U.S. Government Accountability Office (GAO) reported, “Defense Acquisitions: Many Analyses of Alternatives Have Not Provided a Robust Assessment of Weapon System Options” [U.S. Government Accountability Office, Pub. No. GAO-09-665, 2009, p. 1]. In their focused review of 32 Acquisition Category I programs, it was found that 10 did not conduct an Analysis of Alternatives (AoA), but rather focused on an already selected weapon system solution. Prior to Milestone A, the Department of Defense (DoD) requires that service sponsors conduct an Analysis of Alternatives (AoA). The AoA is an analytical comparison of multiple alternatives to be completed prior to committing and investing costly resources to one project or decision. Typically, however, sponsors will circumvent the process in an effort to save money or schedule, and capability requirements are proposed that are so specific that they effectively eliminate all but the preferred concepts, practically ignoring other alternatives. Decision making is one of the most challenging parts of Systems Engineering. How one feeds the decision making process is key to eliminating long term waste. “About three-quarters of a program”s total life cycle cost is influenced by decisions made before it is approved to start development“[U.S. Government Accountability Office, Pub. No. GAO-09-665, 2009, pp. “2]. This study evaluates the positive benefits of defining the problem domain prior to expeditiously turning to the solution domain. The goal in any decision making process is to provide the decision maker with the ability to look into the future, and to make the best possible decision based on past and present information and future predictions. There is a need for approaches that combine available quantitative data with the more subjective knowledge of experts. Decision theory techniques have been successfully used for contrasting expert judgments and making educated choices for many years. For a successful analysis, one must focus on selection of specific criteria that are key performance drivers that can lead to an informed selection of the enabling technology. Understanding the requirements of the end state goal is key to a successful analysis and should also assist in the selection of key performance parameters. A case study example is presented to demonstrate a third tier AoA identifying an enabling technology using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) while successfully accounting for tacit knowledge of expert practitioners. © 2012 Wiley Periodicals, Inc. Syst Eng 16

As budgetary pressure on large complex systems continues to increase, the interest in reusing systems engineering products is emerging. Reuse is the idea of leveraging previously developed products (i.e., hardware, software, designs, outcomes of a process) into a new application for purposes of improving project attributes such as quality, cost, schedule, or risk. While reuse is well documented and commonly practiced in the domains of software and product–line development, limited research has been performed on the (deliberate or accidental) reuse of systems engineering products. This paper classifies such products as those generated as outputs of both the systems engineering process, including architecture elements, requirements, test plans, and interface specifications, as well as the overall system design process. Through reuse, systems engineers may not need to repeat certain development activities associated with these products, potentially reducing effort, or obtaining schedule/risk benefits through the utilization of heritage products. To begin addressing the topic of reuse from a systems engineering perspective, this paper presents a generalized framework for the reuse of systems engineering products; documenting the key considerations, activities, and resources necessary for effective reuse. Building on insight from systems engineering practitioners and previous work by the authors on systems engineering cost estimation, the framework is intended to serve as a tool for planning, executing, and managing reuse activities, as well as identifying reuse opportunities. ©2012 Wiley Periodicals. Inc. Syst Eng 16:

This paper presents a framework aimed at supporting the decision-making process for the preliminary design of system architectures for the extraction of spatially and temporally distributed resources. The goal of the research is to provide a tool to identify “global best” architectures for resource extraction “systems of systems,” which usually differ from the sum of “local best” systems. The framework presented in this paper consists of an integrated model where both the architecture of the system of systems and the design of the individual systems are considered simultaneously. Using this approach, designers are able to gain insights by generating a selection of top-performing concepts. Subsequently, they can analyze those concepts using more sophisticated, albeit more resource-expensive design processes. The implementation of the proposed framework is a complementary tool to existing design practices. It features several advantages such as enabling the analysis of large-scale problems, for which exhaustive enumeration of architectures of systems of systems is not a viable option. The paper first presents an application of the methodology to the architecture of offshore oil and gas production fields. It then shows how to use the methodology for the development of scenario analyses. ©2012 Wiley Periodicals, Inc. Syst Eng 16

There are many references about the characteristics of a good requirement. But what is the process for developing clear, unambiguous requirements, and how do we know when we have defined the requirements successfully? This paper investigates the current state of the methodology for developing complex system requirements. Significant work has been accomplished over the last several years to describe requirements development and systems engineering. This paper identifies and investigates requirements development methodologies and techniques. ©2012 Wiley Periodicals, Inc. Syst Eng 16

As programs rise in intricacy and scope, the number of stakeholders involved also increases, often driving an exponential growth in program complexity. This complexity is caused by the stakeholder relationships which form an underlying system that influences all aspects of the program. Understanding, managing, and leveraging this stakeholder system will greatly increase a program's probability of success. This paper provides a framework for capturing this stakeholder system in a series of architectural views. These architectural products document the program's stakeholder concerns and also illustrate how those stakeholders interrelate over the system's lifecycle. The ultimate objective for the framework and use of the resulting products is to allow for right-sized stakeholder involvement, promote effective use of resources, and increase the probability of overall program success with the assurance of lasting stakeholder commitment. Additionally, this unique insertion of Stakeholder Analysis and Social Network Analysis into an Architecture Framework fulfills an original intent of Architecture Framework, capturing the entire sociotechnical enterprise system. ©2012 Wiley Periodicals, Inc. Syst Eng 16

This study examines the growth of Systems-Centric Systems Engineering (SCSE) graduate programs in the United States and the status of full-time non-tenure-track faculty (NTTF) members within these programs. Growth is measured by the number of master's and PhD students who graduated from those programs. The annual production of master's degree graduates has grown by a factor of 5 during the period, increasing from 312 in 2001 to 1535 in 2010. Furthermore, the six largest SE programs accounted for more than half of those graduates. The annual production of PhD degrees has risen as well, though not as dramatically. In spite of such growth, less than 50% of SCSE programs hire NTTF, and, among them, the majority of the programs (65%) have four or fewer NTTF. Only 24% of the total faculty employed by SCSE programs in 2010 are NTTF, and most of them (67%) spend the majority of their time teaching; 65% of the respondents identified industrial experience as the most attractive reason for hiring them. Among SCSE programs that produced a high number of master's degree graduates, the ones that started between 2001 and 2005 employed a higher number of NTTF compared to those that started before 2001. The roles of NTTF are compared to those of tenured and tenure-track faculty (TTTF). This paper concludes with recommendations on how to best use NTTF. ©2013 Wiley Periodicals, Inc. Syst Eng 16

The purpose of the study was to gain a greater understanding of the use of Systems Practice among engineers working in the Rolls-Royce Defence Sector at its Bristol site and develop hypotheses about its use. This study is part of a larger project to investigate and improve the use and embedding of Systems Practice among engineers at the site. The current situation was studied using a combination of grounded theory and system dynamics, supported by the use of a computer-aided qualitative data analysis software (CAQDAS) package. The results from this work show that Systems Practice is valued as a way of enabling quality in design but engineers find it challenging to adopt because of (i) lack of stakeholder appreciation of its value, (ii) their lack of experience with Systems Engineering, and (iii) logistical issues with its application. This work will be followed by group model building sessions to further develop the findings by identifying interventions to create and assess improvement in Systems Practice, in particular finding errors earlier in the design lifecycle. ©2012 Wiley Periodicals, Inc. Syst Eng 16

This paper examines a set of abstract, top-level principles and subprinciples collected from the literature to determine their usefulness in enabling the avoidance, survival, and recovery from disruptions caused by threats of various sources. The principles are compared to concrete solutions recommended by domain experts in various case studies and to the actual events in those case studies. Also examined are the limitations, conflicts, and vulnerabilities that may be apparent when concrete solutions are created from these principles. The systems considered are physical, organizational, and procedural systems. Examples include cases from fire protection, aviation, railways, and power distribution domains. Threats examined include terrorist attacks, natural disasters, and human and design error. Each principle is found to apply to different phases of the disruption cycle surrounding an encounter with a threat. It is found that principles, in general, cannot be applied singly to a system but must be combined with other principles to enable resilience. System developers in various domains can use the principles to create concrete solutions to characterize a particular system, model that solution, and determine the degree of recovery of the system from a specified threat. ©2012 Wiley Periodicals, Inc. Syst Eng 16

The development of complex sustainable systems presents a number of challenges in requirements engineering (RE). It is difficult to elicit, analyze, and specify interdisciplinary system requirements that have to be fulfilled in order to develop a complex sustainable system. This paper argues for a need for a significant shift in the underlying RE ideas and premises in order to effectively cope with RE challenges of complex sustainable systems development. We present the main requirements for the development of strategic RE methods based on a number of systems, methodological, and epistemological perspective shifts. Strategic RE paradigm shift facilitates adaptation of primarily technological system-specific RE knowledge in order to handle large scale interdisciplinary sustainability-related RE challenges. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Commonality, or the reuse and sharing of components, manufacturing processes, architectures, interfaces, and infrastructure across the members of a product family, is an often leveraged strategy targeted at improving corporate profitability. Commonality strategies are widespread in the literature and in industrial practice, but a clear gap exists: The literature has a distinctly positive bias towards the benefits of commonality, whereas industrial success with commonality has been mixed. This article explores two phenomena, divergence and lifecycle offsets, that may prevent companies from properly assessing and realizing the potential benefits of commonality. Using a multiple case study approach, we trace commonality levels through the lifecycles of seven complex product families that span the aerospace, automotive, semiconductor capital equipment, and printing industries. The case studies indicate that commonality tends to decline over time, a phenomenon we title divergence. In contrast to the prevailing concept of parallel development in product families, we find that lifecycle offsets, or temporal separations between the development, manufacturing, operations, and/or retirement phases of two or more products, are prevalent in industrial practice. Through this exploratory study, we find that lifecycle offsets may reduce the potential benefits of commonality, make the realization of benefits much more difficult, delay the realization of benefits, and reallocate potential benefits across individual products. We predict that lifecycle offsets exacerbate divergence. We propose a framework for categorizing parts-level changes that explicitly recognizes the potential for divergence. We conclude with guidance for product family managers, namely, that commonality be managed dynamically throughout the product family lifecycle, rather than as a static property. Additionally, we articulate the need to make commonality decisions from a product family perspective, a perspective that may lead to decisions that create near-term costs for one variant but result in larger long-term savings for a second variant and for the product family as a whole. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Achieving sustainability involves complex processes of technology, people, institutions, and the environment. The sustainability challenge requires a combination of social, political, and technological efforts. This paper discusses processes for technological change in order to meet the sustainability challenge. These complex processes are found to be a suitable application for systems engineering and for systems architecture in particular. Based on a thorough review of the literature, an architecture framework is developed to support management of portfolios of sustainable technology projects. This architecture framework is validated through a case study process, providing enhancements and lessons learned. The full architecture framework construct and associated proposed implementation approaches are presented, demonstrating the need for and applicability of such systems engineering approaches to achieve sustainability. Lessons learned from case studies and development of representative architectures are also described. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Overall performance of a peer-to-peer system can be highly variable and unpredictable as there is no central authority to set and coordinate the amount of resource contributions made by constituent peers. In this paper, we address the problem of optimal cooperation policy setting for individual peers by taking into account their rationality, and with respect to a set of overall constraints imposed by resource-driven requirements of the system. We formalize distributed cooperation policy setting as an asynchronous distributed decision making (ADDM) process and represent an integrated design for this process in two top-down and bottom-up phases. In top-down design, we specify the overall objective and constraints and in line with them, we synthesize the local objectives of individual peers. We show that the rational peers should continuously adapt their cooperation policies asynchronously and autonomously according to the policies of the other participants in order to maximize their local objectives. To this end, we devise a self-organizing interaction mechanism in the bottom-up phase and demonstrate that it coordinates asynchronous distributed decisions of individual peers with respect to the overall objective and constraints through local interactions. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Resilience means different things in different disciplines. From a systems engineering perspective, we define resilience as the ability of a system to adapt affordably and perform effectively across a wide range of operational contexts, where context is defined by mission, environment, threat, and force disposition. A key issue in engineering resilient systems is the lengthy and costly upfront engineering process, which program managers justifiably find unacceptable. This paper presents how advances in computational technology can potentially transform the system development process in new and novel ways to enable fast, efficient, and inexpensive upfront engineering—the key to engineering resilient systems. These processes, in turn, can enable rapid development, deployment, and operation of affordably adaptable and effective systems. ©2012 Wiley Periodicals, Inc. Syst Eng 16

Supply chains are continuously evolving and adapting systems driven by complex sociotechnical interfirm interactions. Traditional engineering and operations management modeling approaches have primarily focused on technical issues and are not well suited to effectively capture the many complex structural and behavioral aspects of supply chain systems (SCSs). There is growing recognition by the supply chain community of the significant benefits a network analytic lens can provide to understand, design, and manage SCSs. We systematically review and analyze the relevant literature and, drawing on a multidisciplinary theoretical foundation, develop an integrative framework. Our framework identifies three distinct, but interdependent themes that characterize the study of SCSs: SCS network structure (i.e., system architecture), SCS network dynamics (i.e., system behavior), and SCS network strategy (i.e., system policy and control). We elaborate on these themes, review key findings, identify the current limitations and knowledge gaps, and discuss the fundamental benefits derived from adopting an integrated SCSs perspective. We conclude with future research directions for network analysis in SCS design and management, in particular, and complex enterprise systems, in general. ©2012 Wiley Periodicals, Inc. Syst Eng 16: