412 research outputs found
Vehicle Systems Panel deliberations
The Vehicle Systems Panel addressed materials and structures technology issues related to launch and space vehicle systems not directly associated with the propulsion or entry systems. The Vehicle Systems Panel was comprised of two subpanels - Expendable Launch Vehicles & Cryotanks (ELVC) and Reusable Vehicles (RV). Tom Bales, LaRC, and Tom Modlin, JSC, chaired the expendable and reusable vehicles subpanels, respectively, and co-chaired the Vehicle Systems Panel. The following four papers are discussed in this section: (1) Net Section components for Weldalite Cryogenic Tanks, by Don Bolstad; (2) Build-up Structures for Cryogenic Tanks and Dry Bay Structural Applications, by Barry Lisagor; (3) Composite Materials Program, by Robert Van Siclen; (4) Shuttle Technology (and M&S Lessons Learned), by Stan Greenberg
A LinkedIn Analysis of Career Paths of Information Systems Alumni
Information harvested from the LinkedIn profiles for 175 graduates of an Information Systems program at a mid-sized comprehensive university in Southeastern USA are summarized in this investigation. The current investigation was undertaken to examine the extent to which LinkedIn profiles are able to provide a more realistic picture of entry-level jobs held by program alumni and subsequent career progress. In addition, our results suggest that LinkedIn profiles can help answer questions such as: “What jobs do IS graduates get?”, “What does the career of an IS professional typically look like?”, and “Whether IS graduates can successfully transition from technical to managerial positions?”. Our findings also suggest that information in LinkedIn profiles can be used to assess the long-term outcomes of IS programs
From individual vital rates to population dynamics: An integral projection model for European native oysters in a marine protected area
Following an 85% decline in global oyster populations, there has been a recent resurgence in interest in the restoration of the European native oyster Ostrea edulis. Motivations for restoration from environmental stakeholders most often include recovering lost habitats and associated biodiversity and supporting ecosystem function. In coastal communities, another important justification is recovery of traditional and low‐impact fisheries but this has received less attention.
Many restoration projects across Europe focus on the translocation of adult stocks, under the assumption that the limit to population growth and recovery is adult growth and survival. This may not necessarily be the case, especially where knowledge of large extant adult populations exists as in the Blackwater, Crouch, Roach and Colne Marine Conservation Zone in Essex, UK. Identifying what limits population growth for restoration and recovery is an important conservation tool.
Here, the first size‐dependent survival, growth and fecundity data for free‐living O. edulis from a novel field experiment are used to parameterize an Integral Projection Model that examines the sensitivity of a flat oyster population to variation in individual vital rates and to potential harvesting – an original objective of a coastal community‐led restoration project.
Given the high adult fecundity in this species, population recovery is most sensitive to changes in recruitment success; however, elasticity (proportional sensitivity of the population) is more evenly spread across other parameters when recruitment is already high. Based on locally agreed management objectives, recovery to double the current stock biomass should take 16–66 years (mean = 30 years) without active intervention. At that point, harvest rates could be sustained below 5% of the harvestable adult size whilst ensuring λs remains above 1
Numerably Contractible Spaces
Numerably contractible spaces play an important role in the theory of
homotopy pushouts and pullbacks. The corresponding results imply that a number
of well known weak homotopy equivalences are genuine ones if numerably
contractible spaces are involved. In this paper we give a first systematic
investigation of numerably contractible spaces. We list the elementary
properties of the category of these spaces. We then study simplicial objects in
this category. In particular, we show that the topological realization functor
preserves fibration sequences if the base is path-connected and numerably
contractible in each dimension. Consequently, the loop space functor commutes
with realization up to homotopy. We give simple conditions which assure that
free algebras over a topological operad are numerably contractible.Comment: 24 page
Human-like robots for space and hazardous environments
The three year goal for this NASA Senior Design team is to design and build a walking autonomous robotic rover. The rover should be capable of rough terrain crossing, traversing human made obstacles (such as stairs and doors), and moving through human and robot occupied spaces without collision. The rover is also to evidence considerable decision making ability, navigation and path planning skills. These goals came from the concept that the robot should have the abilities of both a planetary rover and a hazardous waste site scout
Robustness of an Artificial Intelligence Solution for Diagnosis of Normal Chest X-Rays
Purpose: Artificial intelligence (AI) solutions for medical diagnosis require
thorough evaluation to demonstrate that performance is maintained for all
patient sub-groups and to ensure that proposed improvements in care will be
delivered equitably. This study evaluates the robustness of an AI solution for
the diagnosis of normal chest X-rays (CXRs) by comparing performance across
multiple patient and environmental subgroups, as well as comparing AI errors
with those made by human experts.
Methods: A total of 4,060 CXRs were sampled to represent a diverse dataset of
NHS patients and care settings. Ground-truth labels were assigned by a
3-radiologist panel. AI performance was evaluated against assigned labels and
sub-groups analysis was conducted against patient age and sex, as well as CXR
view, modality, device manufacturer and hospital site.
Results: The AI solution was able to remove 18.5% of the dataset by
classification as High Confidence Normal (HCN). This was associated with a
negative predictive value (NPV) of 96.0%, compared to 89.1% for diagnosis of
normal scans by radiologists. In all AI false negative (FN) cases, a
radiologist was found to have also made the same error when compared to final
ground-truth labels. Subgroup analysis showed no statistically significant
variations in AI performance, whilst reduced normal classification was observed
in data from some hospital sites.
Conclusion: We show the AI solution could provide meaningful workload savings
by diagnosis of 18.5% of scans as HCN with a superior NPV to human readers. The
AI solution is shown to perform well across patient subgroups and error cases
were shown to be subjective or subtle in nature
Recommended from our members
Developing a biodiversity-based indicator for large-scale environmental assessment: a case study of proposed shale gas extraction sites in Britain
1. Environmental impact assessments are important tools for predicting the consequences of development and changes in land use. These assessments generally use a small subset of total biodiversity – typically rare and threatened species and habitats – as indicators of ecological status. However, these indicators do not necessarily reflect changes in the many more widespread (but increasingly threatened) species, which are important for ecosystem functions. In addition, assessment of threatened species through field surveys is time-consuming and expensive and, therefore, only possible at small spatial scales. In contrast, planning changes in land use over large spatial scales (e.g. national infrastructure projects) require assessment and prioritization of biodiversity over large spatial extents.
2. Here, we provide a method for the assessment of biodiversity, which takes account of species diversity across larger spatial scales, based on occurrence records from 5553 species across 11 taxonomic groups. We compare the efficacy of the biodiversity-based indicator we developed against one based on threatened species only and then use it to consider spatial and temporal patterns in ecological status across Great Britain. Finally, we develop a case study to investigate biodiversity status in regions proposed for shale gas extraction in Great Britain.
3. Our results show a strong relationship between the ecological status of areas defined by all biodiversity versus only threatened species, although they also demonstrate that significant exceptions do exist where threatened species do not always accurately indicate the ecological status of wider biodiversity.
4. Spatial and temporal analyses show large variation in ecological status across Great Britain both within the area made available for shale gas licensing and within individual environmental zones. In total, however, 63% of hectads across Britain have suffered a net reduction in our biodiversity-based indicator since 1970.
5. Synthesis and applications. We provide a method and develop a biodiversity-based indicator for the assessment and prioritization of biodiversity at large spatial scales. We highlight the potential applications of this approach for the prioritization of areas that would benefit from conservation and restoration. We also emphasize the danger of insufficient consideration of more widespread species and not just rare and threatened species and habitats as indicators of ecological status when prioritizing large-scale national infrastructure projects. Our method should be a useful tool to complement existing environmental impact assessment methods
- …