Spacelab system analysis Marshall Avionics System Testbed (MAST)

A synopsis of the visits to avionics test facilities is presented. A list of recommendaions for the MAST facility is also included

Accommodating rising population in rural areas : the case of Loudoun County, Virginia

Population

Spacelab system analysis: The modified free access protocol: An access protocol for communication systems with periodic and Poisson traffic

The protocol definition and terminal hardware for the modified free access protocol, a communications protocol similar to Ethernet, are developed. A MFA protocol simulator and a CSMA/CD math model are also developed. The protocol is tailored to communication systems where the total traffic may be divided into scheduled traffic and Poisson traffic. The scheduled traffic should occur on a periodic basis but may occur after a given event such as a request for data from a large number of stations. The Poisson traffic will include alarms and other random traffic. The purpose of the protocol is to guarantee that scheduled packets will be delivered without collision. This is required in many control and data collection systems. The protocol uses standard Ethernet hardware and software requiring minimum modifications to an existing system. The modification to the protocol only affects the Ethernet transmission privileges and does not effect the Ethernet receiver

How well do diffusion indexes capture business cycles? A spectral analysis

Sampling (Statistics) ; Business cycles

Case Studies of Successful Small Scale Farming in North Carolina

The goal of this study focuses on determining factors that contribute to a successful small farm in North Carolina and on identifying ways to further enhance successful small farming. North Carolina farms vary extensively in size and other characteristics, ranging from very small retirement and residential farms to establishments with millions of dollars in sales. Farming continues to be a distinctive industry in part because most production, even among very large farms, is carried out on family-operated farms whose operators often balance farm and off-farm employment and investment decisions. The case studies of successful small farmers conducted in November 2007 were the primary sources of data. The North Carolina Cooperative Extension Program identified three “successful” farmers from its sampling frame to participate in the case studies. Researchers identified sets of variables associated with small farm success through various literature, published and unpublished reports and recommendations from experts in the field. After the variables were operationalized, a questionnaire was developed as a guide for conducting the case studies interview protocols. Each case study consisted of a one-visit protocol with electronic follow-up. Researchers conducted on-site interviews, and then toured the individual farms. The case study farmers used a diverse mix of enterprises including specialty crops and a combination of marketing strategies. The educational level ranged from post high school to Ph.D. although all farmers attended several workshops. All farmers minimized risk through diversity, contractual sales and insurance. Only one farmer used computers for record keeping and finance. The overall “love of farming” seemed to be the biggest driving force behind the farmer’s view of success.Small Farmer, Agribusiness, Agricultural Finance, Teaching/Communication/Extension/Profession,

Continuum: designing timelines for hierarchies, relationships and scale

Temporal events, while often discrete, also have interesting relationships within and across times: larger events are often collections of smaller more discrete events (battles within wars; artists' works within a form); events at one point also have correlations with events at other points (a play written in one period is related to its performance, or lack of performance, over a period of time). Most temporal visualisations, however, only represent discrete data points or single data types along a single timeline: this event started here and ended there; this work was published at this time; this tag was popular for this period. In order to represent richer, faceted attributes of temporal events, we present Continuum. Continuum enables hierarchical relationships in temporal data to be represented and explored; it enables relationships between events across periods to be expressed, and in particular it enables user-determined control over the level of detail of any facet of interest so that the person using the system can determine a focus point, no matter the level of zoom over the temporal space. We present the factors motivating our approach, our evaluation and implementation of this new visualisation which makes it easy for anyone to apply this interface to rich, large-scale datasets with temporal data

Validation of Factors Influencing Successful Small Scale Farming in North Carolina

This phase of the research project involves developing a survey instrument to test the validity and predictive value of the variables identified in previous case studies. Given the importance of small farm viability, this research project focuses on identifying ways to further enhance successful small farming in North Carolina. The survey instrument was designed to solicit production and financial data, attitudes and beliefs about farming, as well as demographic questions. The results demonstrated that successful farmers indicators were the “love of farming” and “manageable debt”. Other strong indicators of successful farmers included a combination of marketing strategies that utilize technology such as websites as well as local farmers markets and educational level. Knowledge about the successful small farm is likely to provide valuable information about how to evaluate the “successfulness” of small farm operations and produce best practices models for small scale farm operations.Small Farmers, Agribusiness, Agribusiness, Farm Management,

Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)

An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined

Potential vorticity structure in the North Atlantic western boundary current from underwater glider observations

Author Posting. © American Meteorological Society, 2016. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 46 (2016): 327–348, doi:10.1175/JPO-D-15-0112.1.Potential vorticity structure in two segments of the North Atlantic’s western boundary current is examined using concurrent, high-resolution measurements of hydrography and velocity from gliders. Spray gliders occupied 40 transects across the Loop Current in the Gulf of Mexico and 11 transects across the Gulf Stream downstream of Cape Hatteras. Cross-stream distributions of the Ertel potential vorticity and its components are calculated for each transect under the assumptions that all flow is in the direction of measured vertically averaged currents and that the flow is geostrophic. Mean cross-stream distributions of hydrographic properties, potential vorticity, and alongstream velocity are calculated for both the Loop Current and the detached Gulf Stream in both depth and density coordinates. Differences between these mean transects highlight the downstream changes in western boundary current structure. As the current increases its transport downstream, upper-layer potential vorticity is generally reduced because of the combined effects of increased anticyclonic relative vorticity, reduced stratification, and increased cross-stream density gradients. The only exception is within the 20-km-wide cyclonic flank of the Gulf Stream, where intense cyclonic relative vorticity results in more positive potential vorticity than in the Loop Current. Cross-stream gradients of mean potential vorticity satisfy necessary conditions for both barotropic and baroclinic instability within the western boundary current. Instances of very low or negative potential vorticity, which predispose the flow to various overturning instabilities, are observed in individual transects across both the Loop Current and the Gulf Stream.Glider operations in the Gulf Stream were supported by the National Science Foundation under Grant OCE-0220769. Glider operations in the Gulf of Mexico were supported by BP. R.E.T. was supported by the Penzance Endowed Fund in Support of Assistant Scientists and the Independent Research and Development Program at WHOI.2016-07-0

Evidence for a Molecular Cloud Origin for Gamma-Ray Bursts: Implications for the Nature of Star Formation in the Universe

It appears that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or `dark bursts' for short, occur in clouds of size R > 10L_{49}^{1/2} pc and mass M > 3x10^5L_{49} M_{sun}, where L is the isotropic-equivalent peak luminosity of the optical flash. We show that clouds of this size and mass cannot be modeled as a gas that is bound by pressure equilibrium with a warm or hot phase of the interstellar medium (i.e., a diffuse cloud): Such a cloud would be unstable to gravitational collapse, resulting in the collapse and fragmentation of the cloud until a burst of star formation re-establishes pressure equilibrium within the fragments, and the fragments are bound by self-gravity (i.e., a molecular cloud). Consequently, dark bursts probably occur in molecular clouds, in which case dark bursts are probably a byproduct of this burst of star formation if the molecular cloud formed recently, and/or the result of lingering or latter generation star formation if the molecular cloud formed some time ago. We then show that if bursts occur in Galactic-like molecular clouds, the column densities of which might be universal, the number of dark bursts can be comparable to the number of bursts with detected optical afterglows: This is what is observed, which suggests that the bursts with detected optical afterglows might also occur in molecular clouds. We confirm this by modeling and constraining the distribution of column densities, measured from absorption of the X-ray afterglow, of the bursts with detected optical afterglows: We find that this distribution is consistent with the expectation for bursts that occur in molecular clouds, and is not consistent with the expectation for bursts that occur in diffuse clouds. More...Comment: Accepted to The Astrophysical Journal, 22 pages, 6 figures, LaTe