432 research outputs found
Core drill's bit is replaceable without withdrawal of drill stem - A concept
Drill bit is divided into several sectors. When collapsed, the outside diameter is forced down the drill stem, when it reaches bottom the sectors are forced outward and form a cutting bit. A dulled bit is retracted by reversal of this procedure
The Department of the Navy and the DOD Planning Programming, and Budgeting System (PPBS)
Of the thousands of military officers on active duty, only those who have served in Washington, D.C., since 1961 have had the opportunity for direct involvement in the Department of Defense (DOD) Planning, Programming, and Budgeting System (PPBS), And of these only a relatively few have become intimately associated with all aspects of the multifaceted system that manages DOD\u27s resources, Today PPBS serves as the raison d\u27etre justifying the bulk of the military billets in the Washington D.C., area
Torsionally rigid and thermally stable boom
Design of rigid thermally stable beryllium copper extendible boom for space application
An investigation of the possible existence of an effect of the service tenure upon personality characteristics as measured by the Structured-Objective Rorschach Test (SORT).
http://www.archive.org/details/investigationofp00rushU.S. Navy (U.S.N.) author
A kinetic Monte Carlo approach to study fluid transport in pore networks
The mechanism of fluid migration in porous networks continues to attract great interest. Darcy’s law (phenomenological continuum theory), which is often used to describe macroscopically fluid flow through a porous material, is thought to fail in nano-channels. Transport through heterogeneous and anisotropic systems, characterized by a broad distribution of pores, occurs via a contribution of different transport mechanisms, all of which need to be accounted for. The situation is likely more complicated when immiscible fluid mixtures are present. To generalize the study of fluid transport through a porous network, we developed a stochastic kinetic Monte Carlo (KMC) model. In our lattice model, the pore network is represented as a set of connected finite volumes (voxels), and transport is simulated as a random walk of molecules, which “hop” from voxel to voxel. We simulated fluid transport along an effectively 1D pore and we compared the results to those expected by solving analytically the diffusion equation. The KMC model was then implemented to quantify the transport of methane through hydrated micropores, in which case atomistic molecular dynamic simulation results were reproduced. The model was then used to study flow through pore networks, where it was able to quantify the effect of the pore length and the effect of the network’s connectivity. The results are consistent with experiments but also provide additional physical insights. Extension of the model will be useful to better understand fluid transport in shale rocks
Exploring Underserved Communities’ Perspectives on Wilderness Character in Everglades National Park
Issues related to diversity, equity, and inclusion are becoming increasingly important to park and protected area managers. Recently, several Executive Orders have established policies and priorities for steering public lands to better serve the diversity of the US public. Certain groups, compared to the US population at large, are underrepresented as visitors to parks and protected areas in the US, including BIPOC communities (Black, Indigenous, and other People of Color), women, people with disabilities, veterans, people with lower socioeconomic status, and the elderly. This disparity in visitation may be even more pronounced in federally designated wilderness areas. We present a qualitative study focused on the relationships of traditionally underserved groups with Everglades National Park, specifically focusing on perceptions of wilderness character in the Marjory Stoneman Douglas Wilderness. Findings illuminate both perceived benefits of wilderness, including positive mental health, ecosystem services, and a connection to unique aspects of wilderness character in the Everglades, as well as conflicted feelings about wilderness as a place that underemphasizes historic interactions of underrepresented communities with the landscape. We discuss management implications, particularly ways to focus protected area efforts to broaden the relevancy of wilderness lands and better serve diverse populations within local communities
A new approach to generating research-quality data through citizen science: The USA National Phenology Monitoring System
Phenology is one of the most sensitive biological responses to climate change, and recent changes in phenology have the potential to shake up ecosystems. In some cases, it appears they already are. Thus, for ecological reasons it is critical that we improve our understanding of species’ phenologies and how these phenologies are responding to recent, rapid climate change. Phenological events like flowering and bird migrations are easy to observe, culturally important, and, at a fundamental level, naturally inspire human curiosity— thus providing an excellent opportunity to engage citizen scientists. The USA National Phenology Network has recently initiated a national effort to encourage people at different levels of expertise—from backyard naturalists to professional scientists—to observe phenological events and contribute to a national database that will be used to greatly improve our understanding of spatio-temporal variation in phenology and associated phenological responses to climate change.

Traditional phenological observation protocols identify specific dates at which individual phenological events are observed. The scientific usefulness of long-term phenological observations could be improved with a more carefully structured protocol. At the USA-NPN we have developed a new approach that directs observers to record each day that they observe an individual plant, and to assess and report the state of specific life stages (or phenophases) as occurring or not occurring on that plant for each observation date. Evaluation is phrased in terms of simple, easy-to-understand, questions (e.g. “Do you see open flowers?”), which makes it very appropriate for a citizen science audience. From this method, a rich dataset of phenological metrics can be extracted, including the duration of a phenophase (e.g. open flowers), the beginning and end points of a phenophase (e.g. traditional phenological events such as first flower and last flower), multiple distinct occurrences of phenophases within a single growing season (e.g multiple flowering events, common in drought-prone regions), as well as quantification of sampling frequency and observational uncertainties. These features greatly enhance the utility of the resulting data for statistical analyses addressing questions such as how phenological events vary in time and space, and in response to global change. This new protocol is an important step forward, and its widespread adoption will increase the scientific value of data collected by citizen scientists.

On manifolds with nonhomogeneous factors
We present simple examples of finite-dimensional connected homogeneous spaces
(they are actually topological manifolds) with nonhomogeneous and nonrigid
factors. In particular, we give an elementary solution of an old problem in
general topology concerning homogeneous spaces
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