3,450 research outputs found
Forage Yields in Turkey Hill Wilderness in East Texas for White-tailed Deer
Wilderness areas are often considered quality areas where natural processes occur without human activity. It is often assumed that these unmanaged areas will provide and support quality wildlife habitat. The objective of this study was to evaluate the forage production and stocking potential of an unmanaged wilderness area in east Texas. Four different community types were evaluated for forage yield, forage availability, and browse utilization for white-tailed deer. Results show that although a wide range of forage yields were measured in the spring, summer forage yield did not differ among the various communities. Availability also differed between community types, but utilization within each community appears to be lower than what could be supported
DETERMINATION OF A SIMPLE AND ROBUST METHOD TO CALCULATE IGNITION DELAY IN COMPRESSION IGNITION ENGINES: APPLICATION TO DIESEL-BIODIESEL-ETHANOL BLENDS
Today, the automobile industry is under increasing pressure from governments and environmental organizations to lower their carbon footprint. Car manufacturers release new models that follow modern and severe norms of pollutant emissions using eco-friendly technologies. Their strategy follows two main pathways: decarbonization and increase of efficiency. In order to achieve the aforementioned objective, the replacement of fossil fuels with renewable biofuels with lower carbon footprints, such as biodiesel and/or ethanol, contribute to the decarbonization of current internal combustion engines. However, changes in the fuel composition also imply some adjustments in the injection and combustion settings to optimize the engine operation. An important parameter to assess the combustion process in a compression ignition (CI) engine is the ignition delay (ID), defined as the duration between the start of fuel injection (SOI) and the start of combustion (SOC). Different direct and indirect approaches are reported in the literature to measure or calculate the ID. This study investigates two indirect methods based on the measurement of the indicated pressure inside the combustion chamber, throughout the displacement of the piston. These measurements are based on the position of the maximum of the third-order derivative of pressure as a function of the crank angle and the subjective shift from a polytropic compression process, respectively. The objective of the present work is to define an objective criterion to quantify this shift in order to allow a unique determination of the ID, independently of the adopted method. Thus, data of six different fuel blends of diesel-biodiesel-ethanol in a four-stroke CI engine from tests performed at PUC Rio’s Vehicular Engineering Laboratory for different loads and engine speeds were analyzed using the software Matlab. As observed in previous literature, the results show that the addition of biodiesel and ethanol concentration in the blends slightly increases the ID. Moreover, the difference between the experimental pressure with combustion and the calculated pressure in the polytropic compression process at the SOC position is lower as engine load increases and/or engine speed decreases and seems independent of the fuel blend composition. Nonetheless, the variation of the pressure difference at the SOC stays moderate, allowing the determination of a unique value to directly read the ID from the indicated pressure profile, without requiring the smoothing process of the third-order derivative of the pressure
Observing the Geometry of Warped Compactification via Cosmic Inflation
Using DBI inflation as an example, we demonstrate that the detailed geometry
of warped compactification can leave an imprint on the cosmic microwave
background (CMB). We compute CMB observables for DBI inflation in a generic
class of warped throats and find that the results (such as the sign of the tilt
of the scalar perturbations and its running) depend sensitively on the precise
shape of the warp factor. In particular, we analyze the warped deformed
conifold and find that the results can differ from those of other warped
geometries, even when these geometries approximate well the exact metric of the
warped deformed conifold.Comment: 4 pages, 3 figures. v2: References and clarifications adde
Quantum kinetic theory of the filamentation instability
The quantum electromagnetic dielectric tensor for a multi species plasma is
re-derived from the gauge invariant Wigner-Maxwell system and presented under a
form very similar to the classical one. The resulting expression is then
applied to a quantum kinetic theory of the electromagnetic filamentation
instability. Comparison is made with the quantum fluid theory including a Bohm
pressure term, and with the cold classical plasma result. A number of
analytical expressions are derived for the cutoff wave vector, the largest
growth rate and the most unstable wave vector
Academic Libraries, Government Information, and the Persistent Problem of Jargon
The shift to born-digital and digitized materials has ultimately increased access and convenience for users, but in many ways it has also complicated the process of finding information. While users may struggle with catalog interfaces or reading call numbers, most have a basic understanding of how to locate a physical book. But in the digital environment, users have no built-in model for what sequence of clicks or keywords will get them to the information they need. This problem is exacerbated for specialized areas like government information, where more and more data and documents are readily available online via a variety of public web portals. Libraries often curate these portals using research guides or other domain-specific reference websites, providing major points of access for users. However, designing these specialized sites to be user-centered, rather than domaincentered, presents numerous challenges. For instance, how should the needs of different user groups be balanced? How should complex information be structured to support domain experts, while also helping orient and remove barriers for new users? Answering these questions is especially important to Utah State University Libraries (USU), which serve as a Regional Depository for the Federal Depository Library Program (FDLP). USU’s Government Information Department supports not only our community of 25,000 undergraduate and 3,000 graduate students, many of whom learn at a distance, but also local and regional communities as a matter of public access. To be successful, these users need to understand and be able to effectively navigate the “library within a library” that is government information. To support this broad community and their range of needs, our websites need to strike the right balance between straightforward, content-focused design and more supportive, instruction-heavy design
B802: Base-Age Invariant Polymorphic Site Index Curves for Even-Aged Spruce-Fir Stands in Maine
The spruce-fir forest cover type, occupying nearly 8 million acres in Maine, accounts for approximately 50 percent of the growing stock volume in the State. A similar portion of Maine\u27s commercial forest land is owned and managed by forest industry, with spruce and fir being the mainstay of the industry.
Analyses in recent years of Maine\u27s timber supply have shown softwood removals to exceed growth. The dramatic effects of the spruce budworm (Choristoneura.fumiferana (Clemens)) on the spruce-fir forest of Maine has heightened concern over the timber supply. A greater emphasis on management is necessary if timber growth is to keep pace with demand. With increasing demand for timber, and the increasing value of timber products, intensive management is becoming economically feasible. High labor costs have led to an increase in mechanized harvesting. Consequently, the stage has been set for a greater emphasis on even-aged management of the spruce-fir forest type in Maine~ As red spruce (Picea rubens Sarg.), black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.) are the backbone of Maine\u27s forest industry, it is desirable to identify those sites best suited to the growth of these species.
An easily attained and sufficiently accurate method of estimating the relative quality of a particular site is essential to sound forest management. Site index, defined as being the height attained by the dominant stand at an arbitrarily chosen age, commonly 50 years in the northeastern United States, has been the most widely used measure of site quality. In addition to being an easily measured indicator of relative site quality, site index provides a crucial parameter in the estimation of the ultimate capability of forest land to produce wood volume.https://digitalcommons.library.umaine.edu/aes_bulletin/1100/thumbnail.jp
Tip casing heat transfer measurements of a film-cooled turbine stage in a short duration facility
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references (p. 139-140).by Bret P. Van Poppel.S.M
Functional Neuroplasticity in the Nucleus Tractus Solitarius and Increased Risk of Sudden Death in Mice with Acquired Temporal Lobe Epilepsy
Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in individuals with refractory acquired epilepsy. Cardiorespiratory failure is the most likely cause in most cases, and central autonomic dysfunction has been implicated as a contributing factor to SUDEP. Neurons of the nucleus tractus solitarius (NTS) in the brainstem vagal complex receive and integrate vagally mediated information regarding cardiorespiratory and other autonomic functions, and GABAergic inhibitory NTS neurons play an essential role in modulating autonomic output. We assessed the activity of GABAergic NTS neurons as a function of epilepsy development in the pilocarpine-induced status epilepticus (SE) model of temporal lobe epilepsy (TLE). Compared with age-matched controls, mice that survived SE had significantly lower survival rates by 150 d post-SE. GABAergic NTS neurons from mice that survived SE displayed a glutamate-dependent increase in spontaneous action potential firing rate by 12 wks post-SE. Increased spontaneous EPSC frequency was also detected, but vagal afferent synaptic release properties were unaltered, suggesting that an increase in glutamate release from central neurons developed in the NTS after SE. Our results indicate that long-term changes in glutamate release and activity of GABAergic neurons emerge in the NTS in association with epileptogenesis. These changes might contribute to increased risk of cardiorespiratory dysfunction and sudden death in this model of TLE
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