@article{long_morkos_ferguson_2021, title={Toward Quantifiable Evidence of Excess' Value Using Personal Gaming Desktops}, volume={143}, ISSN={["1528-9001"]}, DOI={10.1115/1.4049520}, abstractNote={Abstract
               Complex systems may operate in scenarios where the current requirements were “unknown” at the time of their original design. Such “unknown” requirements might be outside the probability distribution expected during the design phase or, more drastically, might not have been predicted. Yet, not meeting these “unknown” requirements can significantly reduce system value. Engineering design researchers have begun addressing this challenge by exploring how incorporating margins when the system is being designed—a form of strategic inefficiency—might increase a system’s total lifetime value by reducing sensitivity to requirement changes and truncating change propagation. Quantitatively studying excess margin beyond what is required for known uncertainties has been particularly challenging as information is needed about how requirements change, how system performance is impacted by requirement changes, and how components are priced. A quantitative study around excess using 20 years of data for desktop computers, video game consoles, and video games is developed. Evidence is provided that excess can improve end-user system value when future requirements are unknown. This paper also advances the notion of strategic excess (excess incorporated in a single component), showing as one example that excess RAM would have improved system performance by 14% (on average) for 7% of total system cost. In demonstrating the value of excess, we strengthen the argument that engineers (and end-users) should embrace strategic inefficiencies—even though they might never be used—and further study the implications of system architecture and module interfaces decisions.}, number={3}, journal={JOURNAL OF MECHANICAL DESIGN}, author={Long, Daniel and Morkos, Beshoy and Ferguson, Scott}, year={2021}, month={Mar} }
 @article{long_ferguson_2021, title={Assessing Lifecycle Value Using Object-Based Modeling by Incorporating Excess and Changeability}, volume={143}, ISSN={["1528-9001"]}, DOI={10.1115/1.4048218}, abstractNote={Abstract
               Prior research suggests that excess (purposeful inclusion of margin beyond what is required for known system uncertainties) can limit change propagation and reduce system modifications. Reducing change costs increases system flexibility, permitting adaptions that satisfy uncertain future requirements. The benefits of excess, however, must be traded against higher costs of the initial system and likely performance decreases. Assessing the benefits and costs of excess requires evaluating what forms, locations, and magnitudes of excess inclusion are optimal. This paper improves the state-of-the-art in two ways. First, prior research has generally assessed excess in system-level properties (aggregating component properties into a single metric). The approach presented in this paper extends excess assessment to the component level so that the effects of excess on change propagation may be explicitly captured. Second, this approach holistically assesses the value of excess by evaluating both its costs and benefits. The approach borrows from Decision-Based Design and Model Based System Engineering (MBSE) in creating a generic modeling method capable of excess valuation. A desktop computer example is used for demonstrating how excess is valued in a system and the potential gains associated with excess inclusion when mining cryptocurrency. A single component optimization of the power supply capacity for the desktop is assessed to be 750 W, which balances the initial cost against the future flexibility. A system-level optimization then demonstrates the identification of critical change propagation pathways and illuminates both where and how excess may be included to inhibit change propagation. This key component was identified as the motherboard-central processing unit (CPU) slot in the tested systems.}, number={5}, journal={JOURNAL OF MECHANICAL DESIGN}, author={Long, Daniel and Ferguson, Scott}, year={2021}, month={May} }
 @article{long_ferguson_2020, title={Studying Dynamic Change Probabilities and Their Role in Change Propagation}, volume={142}, ISSN={["1528-9001"]}, DOI={10.1115/1.4046674}, abstractNote={Abstract
               Long-lived systems are likely to experience many independent modifications during their lifecycles. Prior literature provides tools for predicting how a change in a fixed system is likely to propagate, but these tools do not address change propagation across multiple, independent modifications. The phenomenon of a modification consuming excess, thereby increasing the likelihood of change propagation in future modifications, is studied in this work as dynamic change probabilities (DCP). This research builds on change propagation techniques, network theory, and excess to provide high-level guidance about how DCP may alter change propagation within a system over time. A sample of existing and synthetic systems are explored, as we show that the rate of change likelihood increase following a modification depends on the number of components (nodes), the dependencies between components (edges), and initial change propagation probability values (edge weights). Results also show that excess placement in specific components, and the presence of system hubs (high-degree components), can mitigate the impact of excess consumption when multiple system modifications are made over time.}, number={10}, journal={JOURNAL OF MECHANICAL DESIGN}, author={Long, Daniel and Ferguson, Scott}, year={2020}, month={Oct} }
 @inproceedings{long_ferguson_2017, title={A case study of evolvability and excess on the B-52 stratofortress and FA-18 hornet}, DOI={10.1115/detc2017-68287}, abstractNote={The moment a system is put into service it begins to lose value as technological and societal changes accrue while the system is frozen in the state it was constructed. System decision makers are faced with the choice of accepting a decline in performance, updating the design, or retiring the system. Each time a decision maker faces these alternatives, the value of the available options must be evaluated to determine the preferred course of action. A design that can adapt to changes with minimal cost should provide more value over a longer period than a system that is initially less costly, but less adaptable. This is especially desirable for systems that have large initial costs and/or a lengthy development cycle. The purpose of this paper is to evaluate the United States Air Force (USAF) B-52 Stratofortress and the United States Navy (USN) F/A-18 Hornet to characterize the changes in desired capabilities and what system attributes allowed them to either successfully adapt or prevented them from adapting. These observations allow the development of heuristics that designers can use during system design to enhance system lifetime value.}, booktitle={Proceedings of the asme international design engineering technical conferences and computers and information in engineering conference, 2017, vol 4}, author={Long, D. and Ferguson, S.}, year={2017} }