2,544 research outputs found

    Comparison of ear corn plus supplement, shelled corn plus protein supplement and complete mixed rations for growing and finishing swine

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    The purposes of this experiment were: (1) to compare and evaluate the effect of ear corn, shelled corn and a complete mixed ration when fed to growing and finishing swine; (2) to further determine the effect of each one on rate of gain; (3) to compare the feed efficiency of each type of feed in terms of total pounds required and the total cost of each; and (4) to determine the effect of each type of feed on backfat thickness

    The effect of oxygenates on the oligomerisation of propene over zeolite ZSM-5

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    The oligomerisation of alkenes such as propene and butene represents an important route to the production of environmentally clean transportation fuels. When these olefins originate from Fischer-Tropsch product streams they are often contaminated with small amounts of oxygenates such as acetic acid, ethanol, butanol, methyl-ethyl-ketone (MEK), acetone and water. Complex feeds can result in competitive reaction between the feed components and may result in observed selectivities that cannot be predicted from pure component data alone. ZSM-5 has been shown to be an excellent catalyst for alkene oligomerisation and is also active for the conversion of oxygenates. When pure oxygenates are fed over ZSM-5 at oligomerisation temperatures, acetone and MEK cause the catalyst to deactivate and the conversions are low whereas ethanol and n-butanol are completely converted and no deactivation occurs. At 250掳C acetic acid undergoes a low conversion (4%) and at higher temperatures a decrease in conversion is also observed with time. The decrease in conversion of acetone has been attributed to the formation of a surface cyclic ketonic species. During acetic acid reaction dehydroxylation of the zeolite has been proposed as the cause of decreasing activity with time but this work has shown that the catalyst is regenerable and the acidity of the catalyst, as determined by ammonia TPD, remains unchanged after reaction with acetic acid. The propene oligomerisation and hexane cracking activity of ZSM-5 (Si/Al = 30) is reduced when the catalyst is exposed to oxygenates such as acetic acid, ethanol, n-butanol, MEK, acetone and water (mole fraction in feed < 0.01). In the case of all except acetic acid the activity is almost completely restored when the oxygenate is removed. Acetic acid causes irreversible loss of activity for propene oligomerisation and hexane cracking at 250掳C. For MEK and acetone the activity for propene oligomerisation is restored to a greater extent (90% for acetone and 50-60% for MEK) than acetic acid but not fully. The decrease in activity for propene oligomerisation and hexane cracking at 250掳C is proposed to be due to site poisoning by preferential strong adsorption of the oxygenates, especially acetic acid, onto the zeolite surface. An adsorption complex for acetic acid and the surface hydroxyls has been proposed in which the bond angles and lengths of the molecule are similar to those observed in the formation of the acetic acid dimer, consistent with the proposed strong adsorption

    Perceptions Of Undergraduate Business Students Toward Online Courses In Higher Education Expanded And Revisited: Do Gender, Age, And/Or Past Experiences Make A Difference?

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    This study analyzes the perceptions and preferences of a group of undergraduate business students with respect to taking on-line or distance education courses. In this last decade, distant learning programs have become very popular, and the number of offerings continues to increase.&nbsp; The growing popularity of this medium for instruction is due to a combination of factors.&nbsp; Technological advances have made the availability both economical and practical. The economic advantages of distributing scarce resources, geographically and temporally, to students in remote locations provide a broader market for distance education. Additionally, the increasing demand from students to acquire education at times that are convenient given their busy schedules and personal commitments makes distance education attractive to working learners (Roberts 1998). The new opportunities distance learning has provided have enabled students to create an atmosphere for learning at home.&nbsp;The distance debate usually focuses on issues related to student learning and outcomes and student attitudes as compared to traditional classroom-based settings (Phillips, 1998; Webster &amp; Hackley, 1997).&nbsp; This study attempts to address these and other topics such as what is distance learning, what are the advantages and disadvantages, and what changes can be made to improve this type of learning.&nbsp; This research is intended to give students a realistic expectation of what to anticipate from distance learning courses based on information we have found and studies we have done.&nbsp; It is important that students have a realistic perception of the distant learning experience

    Measurement of the Surface and Underground Fast Neutron Spectra with the UMD/NIST Fast Neutron Spectrometers

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    The typical fast neutron detector falls into one of two categories, Bonner sphere spectrometers and liquid scintillator proton recoil detectors. These two detector types have traditionally been used to measure fast neutrons at the surface and in low background environments. The cosmogenic neutron spectrum and flux is an important parameter for a number of experimental efforts, including procurement of low background materials and the prediction of electronic device faults. Fast neutrons can also cause problems for underground low-background experiments, through material activation or signals that mimic rare events. Current detector technology is not sufficient to properly characterize these backgrounds. To this end, the University of Maryland and the National Institute of Standards and Technology designed, developed, and deployed two Fast Neutron Spectrometers (FaNS) comprised of plastic scintillator and 3He proportional counters. The detectors are based upon capture-gated spectroscopy, a technique that demands a delayed coincidence between a neutron scatter and the resulting neutron capture after thermalization. This technique provides both particle identification and knowledge that the detected neutron fully thermalized. This improves background rejection capabilities and energy resolution. Presented are the design, development, and deployment of FaNS-1 and FaNS-2. Both detectors were characterized using standard fields at NIST, including calibrated 252Cf neutron sources and two monoenergetic neutron generators. Measurements of the surface fast neutron spectrum and flux have been made with both detectors, which are compared with previous measurements by traditional detectors. Additionally, FaNS-1 was deployed at the Kimballton Underground Research Facility (KURF) in Ripplemead, VA. A measurement of the fast neutron spectrum and flux at KURF is presented as well. FaNS-2 is currently installed in a shallow underground laboratory where it is measuring the muon-induced neutron flux and spectrum

    Airborne Subscale Transport Aircraft Research Testbed: Aircraft Model Development

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    The Airborne Subscale Transport Aircraft Research (AirSTAR) testbed being developed at NASA Langley Research Center is an experimental flight test capability for research experiments pertaining to dynamics modeling and control beyond the normal flight envelope. An integral part of that testbed is a 5.5% dynamically scaled, generic transport aircraft. This remotely piloted vehicle (RPV) is powered by twin turbine engines and includes a collection of sensors, actuators, navigation, and telemetry systems. The downlink for the plane includes over 70 data channels, plus video, at rates up to 250 Hz. Uplink commands for aircraft control include over 30 data channels. The dynamic scaling requirement, which includes dimensional, weight, inertial, actuator, and data rate scaling, presents distinctive challenges in both the mechanical and electrical design of the aircraft. Discussion of these requirements and their implications on the development of the aircraft along with risk mitigation strategies and training exercises are included here. Also described are the first training (non-research) flights of the airframe. Additional papers address the development of a mobile operations station and an emulation and integration laboratory