Modeling Median Will-Cost Estimates for Defense Acquisition Programs

Purpose: The introduction of “should cost” in 2011 required all Major Defense Acquisition Programs (MDAP) to create efficiencies and improvements to reduce a program’s “will-cost” estimate. Realistic “will-cost” estimates are a necessary condition for the “should cost” analysis to be effectively implemented. Owing to the inherent difficulties in establishing a program’s will-cost estimate, this paper aims to propose a new model to infuse realism into this estimate. Design/methodology/approach: Using historical data from 73 Departments of Defense programs as recorded in the selected acquisition reports (SARs), the analysis uses mixed stepwise regression to predict a program’s cost from Milestone B (MS B) to initial operational capability (IOC)

Estimating an Acquisition Program’s Likelihood of Staying within Cost and Schedule Bounds

Program managers use prior experience to spot potential programmatic areas of concern. Augmenting this experience, the authors present an empirical procedure to estimate the likelihood of a program not exceeding two schedule and cost thresholds: (a) 15 percent of the initial total acquisition cost estimate from Milestone (MS) B to Initial Operating Capability (IOC); and (b) 15 percent of the estimated length (in months) between MS B and IOC—the second bound being 25 percent of the cost and schedule estimate. Using logistic regression and odds ratios, the authors analyze 49 Department of Defense programs and generally find that electronic system programs, extremely large programs (exceeding $17.5 billion in Base Year 2017 dollars), programs procuring smaller quantities of units, and programs with shorter schedules (less time from MS A to MS B and projected time from MS B to IOC) experience smaller percentages of cost growth and schedule slippage

Book Reviews

Book reviews of: Bound in Wedlock: Slave and Free Black Marriage in the Nineteenth Century. By Tera W. Hunter. (Cambridge: The Belknap Press of Harvard University Press, 2017. 404 pp. $29.95, cloth. ISBN: 9780674045712.) Delta Epiphany: Robert F. Kennedy in Mississippi. By Ellen B. Meacham. (Jackson: University Press of Mississippi, 2018. Acknowledgements, source notes, bibliography, about the photographers, index, Pp. xi, 293.$28 cloth. ISBN 9781496817457.) Let the People See: The Story of Emmett Till. By Elliott J. Gorn. (New York: Oxford University Press, 2018. Acknowledgements, source notes, bibliography, index, Pp. xi, 400. $27.95 hardcover. ISBN: 9780199335122.) The Ordeal of the Reunion: A New History of Reconstruction. By Mark Wahlgren Summers. (Chapel Hill: The University of North Carolina Press, 2014. 528 pp., 21 halftones, notes, bibl., index.$40.00 cloth. ISBN: 978-1-4696-1757-2.) Stepdaughters of History: Southern Women and the American Civil War. By Catherine Clinton. (Baton Rouge: Louisiana State University Press, 2016. $48.00 hardback. ISBN: 978807164570.) Frontiers of Science: Imperialism and Natural Knowledge in the Gulf South Borderlands, 1500- 1850. By Cameron B. Strang. (Chapel Hill, NC: University of North Carolina Press, 2018. Acknowledgements, illustrations, index. Pp. vii, 357.$39.95 Cloth. ISBN: 9781469640471.) Vicksburg, Grant’s Campaign that Broke the Confederacy. By Donald L. Miller. (New York: Simon & Schuster, 2019. Notes, illustrations, index. Pp. 663. $35.00.

Understanding variation in salamander ionomes: A nutrient balance approach

Ecological stoichiometry uses information on a few key biological elements (C, N, and P) to explain complex ecological patterns. Although factors driving variation in these elements are well-established, expanding stoichiometric principles to explore dynamics of the many other essential elements comprising biological tissues (i.e., the ionome) is needed to determine their metabolic relationships and better understand biological control of elemental flows through ecosystems. 2. In this paper, we report observations of ionomic variation in two species of salamander (Ambystoma opacum and A. talpoideum) across ontogenic stages using specimens from biological collections of two wetlands sampled over a 30-year period. This unique data set allowed us to explore the extent of ionomic variation between species, among ontogenic stages, between sites, and through time. 3. We found species- and to a lesser extent site-specific differences in C, N, and P along with 13 other elements forming salamander ionomes but saw no evidence of temporal changes. Salamander ionomic composition was most strongly related to ontogeny with relatively higher concentrations of many elements in adult males (i.e., Ca, P, S, Mg, Zn, and Cu) compared to metamorphic juveniles, which had greater amounts of C, Fe, and Mn. 4. In addition to patterns of individual elements, covariance among elements was used to construct multi-elemental nutrient balances, which revealed differences in salamander elemental composition between species and sites and changes in elemental proportions across ontogenic development. These multi-elemental balances distinguished among species-site-ontogenic stage groups better than using only C, N, and P. 5. Overall, this study highlights the responsiveness of consumer ionomes to life-history and environmental variation while reflecting underlying relationships among elements tied to biological function. As such, ionomic studies can provide important insights into factors shaping consumer elemental composition and for predicting how these changes might affect higher-order ecological processes

Comparison of Airborne and Ground-Based Function Allocation Concepts for NextGen Using Human-In-The-Loop Simulations

This paper presents an air/ground functional allocation experiment conducted by the National Aeronautics and Space Administration (NASA) using two human-in-the-Loop simulations to compare airborne and ground-based approaches to NextGen separation assurance. The approaches under investigation are two trajectory-based four-dimensional (4D) concepts; one referred to as "airborne trajectory management with self-separation" (airborne) the other as "ground-based automated separation assurance" (ground-based). In coordinated simulations at NASA's Ames and Langley Research Centers, the primary operational participants -controllers for the ground-based concept and pilots for the airborne concept - manage the same traffic scenario using the two different 4D concepts. The common scenarios are anchored in traffic problems that require a significant increase in airspace capacity - on average, double, and in some local areas, close to 250% over current day levels - in order to enable aircraft to safely and efficiently traverse the test airspace. The simulations vary common independent variables such as traffic density, sequencing and scheduling constraints, and timing of trajectory change events. A set of common metrics is collected to enable a direct comparison of relevant results. The simulations will be conducted in spring 2010. If accepted, this paper will be the first publication of the experimental approach and early results. An initial comparison of safety and efficiency as well as operator acceptability under the two concepts is expected

Comparison of Ground-Based and Airborne Function Allocation Concepts for NextGen Using Human-In-The-Loop Simulations

Investigation of function allocation for the Next Generation Air Transportation System is being conducted by the National Aeronautics and Space Administration (NASA). To provide insight on comparability of different function allocations for separation assurance, two human-in-the-loop simulation experiments were conducted on homogeneous airborne and ground-based approaches to four-dimensional trajectory-based operations, one referred to as ground-based automated separation assurance (groundbased) and the other as airborne trajectory management with self-separation (airborne). In the coordinated simulations at NASA s Ames and Langley Research Centers, controllers for the ground-based concept at Ames and pilots for the airborne concept at Langley managed the same traffic scenarios using the two different concepts. The common scenarios represented a significant increase in airspace demand over current operations. Using common independent variables, the simulations varied traffic density, scheduling constraints, and the timing of trajectory change events. Common metrics were collected to enable a comparison of relevant results. Where comparisons were possible, no substantial differences in performance or operator acceptability were observed. Mean schedule conformance and flight path deviation were considered adequate for both approaches. Conflict detection warning times and resolution times were mostly adequate, but certain conflict situations were detected too late to be resolved in a timely manner. This led to some situations in which safety was compromised and/or workload was rated as being unacceptable in both experiments. Operators acknowledged these issues in their responses and ratings but gave generally positive assessments of the respective concept and operations they experienced. Future studies will evaluate technical improvements and procedural enhancements to achieve the required level of safety and acceptability and will investigate the integration of airborne and ground-based capabilities within the same airspace to leverage the benefits of each concept

Hunting and mountain sheep: Do current harvest practices affect horn growth?

The influence of human harvest on evolution of secondary sexual characteristics has implications for sustainable management of wildlife populations. The phenotypic consequences of selectively removing males with large horns or antlers from ungulate populations have been a topic of heightened concern in recent years. Harvest can affect size of horn-like structures in two ways: (a) shifting age structure toward younger age classes, which can reduce the mean size of horn-like structures, or (b) selecting against genes that produce large, fast-growing males. We evaluated effects of age, climatic and forage conditions, and metrics of harvest on horn size and growth of mountain sheep (Ovis canadensis ssp.) in 72 hunt areas across North America from 1981 to 2016. In 50% of hunt areas, changes in mean horn size during the study period were related to changes in age structure of harvested sheep. Environmental conditions explained directional changes in horn growth in 28% of hunt areas, 7% of which did not exhibit change before accounting for effects of the environment. After accounting for age and environment, horn size of mountain sheep was stable or increasing in the majority (similar to 78%) of hunt areas. Age-specific horn size declined in 44% of hunt areas where harvest was regulated solely by morphological criteria, which supports the notion that harvest practices that are simultaneously selective and intensive might lead to changes in horn growth. Nevertheless, phenotypic consequences are not a foregone conclusion in the face of selective harvest; over half of the hunt areas with highly selective and intensive harvest did not exhibit age-specific declines in horn size. Our results demonstrate that while harvest regimes are an important consideration, horn growth of harvested male mountain sheep has remained largely stable, indicating that changes in horn growth patterns are an unlikely consequence of harvest across most of North America.Utah Division of Wildlife Resources; National Wild Sheep Foundation (WSF); Wyoming Wild Sheep Foundation; Alberta Wild Sheep Foundation; California Wild Sheep Foundation; Arizona Desert Bighorn Sheep Society; Wyoming Governor's Big Game License Coalition; Iowa Foundation for North American Wild Sheep; Utah Foundation for North American Wild Sheep; Pope and Young ClubOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Evaluation of automated airway morphological quantification for assessing fibrosing lung disease

Abnormal airway dilatation, termed traction bronchiectasis, is a typical feature of idiopathic pulmonary fibrosis (IPF). Volumetric computed tomography (CT) imaging captures the loss of normal airway tapering in IPF. We postulated that automated quantification of airway abnormalities could provide estimates of IPF disease extent and severity. We propose AirQuant, an automated computational pipeline that systematically parcellates the airway tree into its lobes and generational branches from a deep learning based airway segmentation, deriving airway structural measures from chest CT. Importantly, AirQuant prevents the occurrence of spurious airway branches by thick wave propagation and removes loops in the airway-tree by graph search, overcoming limitations of existing airway skeletonisation algorithms. Tapering between airway segments (intertapering) and airway tortuosity computed by AirQuant were compared between 14 healthy participants and 14 IPF patients. Airway intertapering was significantly reduced in IPF patients, and airway tortuosity was significantly increased when compared to healthy controls. Differences were most marked in the lower lobes, conforming to the typical distribution of IPF-related damage. AirQuant is an open-source pipeline that avoids limitations of existing airway quantification algorithms and has clinical interpretability. Automated airway measurements may have potential as novel imaging biomarkers of IPF severity and disease extent

Latitudinal patterns in stabilizing density dependence of forest communities

Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1, 2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4, 5, which increases community stabilization, species coexistence and the diversity of local tree species6, 7. Previous analyses supporting such a latitudinal gradient in CNDD8, 9 have suffered from methodological limitations related to the use of static data10–12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14, 15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests