244 research outputs found

    Control Of Flexible Structures-2 (COFS-2) flight control, structure and gimbal system interaction study

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    The second Control Of Flexible Structures Flight Experiment (COFS-2) includes a long mast as in the first flight experiment, but with the Langley 15-m hoop column antenna attached via a gimbal system to the top of the mast. The mast is to be mounted in the Space Shuttle cargo bay. The servo-driven gimbal system could be used to point the antenna relative to the mast. The dynamic interaction of the Shuttle Orbiter/COFS-2 system with the Orbiter on-orbit Flight Control System (FCS) and the gimbal pointing control system has been studied using analysis and simulation. The Orbiter pointing requirements have been assessed for their impact on allowable free drift time for COFS experiments. Three fixed antenna configurations were investigated. Also simulated was Orbiter attitude control behavior with active vernier jets during antenna slewing. The effect of experiment mast dampers was included. Control system stability and performance and loads on various portions of the COFS-2 structure were investigated. The study indicates possible undesirable interaction between the Orbiter FCS and the flexible, articulated COFS-2 mast/antenna system, even when restricted to vernier reaction jets

    Toward optimal water management in Colorado's Lower Arkansas River Valley: monitoring and modeling to enhance agriculture and environment

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    Edition 1.0 June 2006.Includes bibliographical references (pages 42-44).For several years, Colorado State University has been documenting flow and water quality conditions in Colorado's Lower Arkansas River Valley with the goal of providing data and models that water users and managers can use to enhance both agriculture and the environment in the Valley. Extensive measurements are being made in the field, and some previously gathered data are still undergoing analysis. Models of the irrigated stream-aquifer system are under development, calibration, and refinement. Potential strategies for improving conditions in the river valley are being formulated and investigated. Small-scale pilot testing of solutions are scheduled to begin during the summer of 2006. The results presented in this technical report are published as a benchmark to document completion of the first phase of this work. They also provide broad information in support of current decision making in the river valley and hopefully will stimulate feedback and discussion. Some of the information presented here is provisional since it is still undergoing refinement and expansion.This research was partially funded by the U.S. Department of the Interior Geological Survey and Colorado Water Resources Research Institute Project on Grant Number 01HQGR0077, Project 2002CO6B and the Colorado Agricultural Experiment Station project COL00694 entitled 'Multidisciplinary Research on Salinity Issues in the Arkansas River Valley.

    14-06 Development of Safety Performance Functions and Other Decision Support Tools to Assess Pedestrian and Bicycle Safety

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    A field study was performed at 40 uncontrolled midblock crosswalks and 26 signalized intersections on low-speed roadways selected from the areas surrounding three major urban college campuses across lower Michigan. An array of existing traffic control devices existed at the study sites, including various crosswalk marking strategies, along with additional treatments, such as pedestrian hybrid beacons (PHBs), rectangular rapid-flashing beacons (RRFBs) and single in-street R1-6 signs. The sites also collectively included a diverse set of roadway and traffic characteristics, including crossing widths, number of lanes, and median presence, along with vehicular, pedestrian, and bicyclist volumes. Three primary evaluations were performed for the midblock segments and signalized intersection study sites, including: driver yielding compliance, vehicle-pedestrian conflicts, and non-motorized traffic crash data. The yielding compliance study found that the type of crosswalk treatment has a strong influence over driver yielding compliance. While yielding compliance improves substantially when crosswalk markings are utilized, the highest compliance rates are achieved when an additional enhancement device (i.e., RRFB, PHB, or R1-6 sign), is also provided. To supplement small crash sample sizes at the study sites, Michigan statewide pedestrian and bicyclist crash data were collected and utilized to develop safety performance functions (SPFs) and other methods for predicting pedestrian and bicyclist crashes at road segments and intersections. Because pedestrian and bicyclist volumes were not available statewide, each model was developed for pedestrian and bicycle crashes based solely on vehicular AADT. In general, the models showed that pedestrian and bicycle crashes tend to increase with increasing traffic volumes. However, even in the highest volume cases, only a fraction of crashes involved a pedestrian or bicyclist. Pedestrian and bicycle crashes were further estimated based on the respective proportion of the Michigan specific SPF models for total crashes. The primary limitation towards prediction of pedestrian and bicycle crashes is the lack of a reliable exposure data to represent the amount of pedestrian or bicyclist activity on a given segment or intersection

    Comparison of Ammonia Emissions from Poultry Houses Based on Diurnal Integration vs. Daily Means of Gas Concentration and Building Ventilation Rate

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    Quantification of aerial emissions from animal feeding operations (AFOs) requires the knowledge of both concentration of the constituent of interest and the ventilation rate (VR) through the emitting source. Daily emissions can be and are normally determined from diurnal integration of frequent measurements, referred to as the diurnal integration method (DIM), but is resource intensive. Alternatively, daily emission may be more economically estimated from daily means of concentration and VR, referred to as diurnal means method (DMM). In this study, DMM was compared with DIM in determining daily ammonia (NH3) emissions from mechanically ventilated laying-hen, turkey and broiler houses under U.S. production conditions. Results show that deviations in daily NH3 emissions between DMM and DIM methods ranged from as small as \u3c 3% (e.g., for medium age turkey under both cold and warm weather conditions) to as high as 98% (e.g., broiler houses in summer). Deviations were related with coefficient of variation (CV) of VR or NH3 concentration, although prediction of the deviation using CV of VR and/or NH3 concentration alone will likely not produce reliable results. The study suggests that caution must be taken when using DMM to estimate daily NH3 emissions from poultry houses under typical US production conditions

    Air Exchange Rate in a Horse Trailer During Road Transport

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    Horses traveling by road commonly experience heat stress conditions and poor air quality, which may be caused by insufficient ventilation; however, there are few estimates of air exchange in a horse trailer during transport. Air exchange rate was measured at ten locations within a four-horse trailer (internal volume 18.5 m3) using tracer gas decay measurement to assess the adequacy of ventilation. Three vehicle speeds (13, 48, and 97 km h-1) and three window configurations (all windows and roof vents closed, all windows open, all windows open and roof vents open forward) were tested with and without animals present in the trailer. External air temperature ranged from 22.3°C to 28.3°C with an average of 25.3°C, and internal air temperature ranged from 29.9°C to 34.8°C with an average of 31.3°C with animals present. Air exchange rate increased with vehicle speed and open window and vent area. The average air exchange rate over all vehicle speeds and ventilation configurations was 0.52 min-1 with animals present and 0.76 min-1 without animals. Without animals present, the maximum mean exchange rate was 1.42 min-1 at 97 km h-1 at the rear left window with all windows and vents open; the lowest mean exchange rate was 0.12 min-1 at 13 km h-1 with all windows and vents closed at the lower position of the rearmost stall divider. With animals present, the maximum air exchange rate observed was 0.84 min-1 with all windows and vents open and traveling at 97 km h-1. Ventilation in the trailer was not adequate when compared to recommendations for stabled horses for any combination of vehicle speed or ventilation configuration. Increasing open vent area, either by increasing the number and size of roof vents or the size of windows in the sidewall, would be the most cost-effective means of increasing air exchange in a horse trailer

    The distribution of selected localized alien plant species in Hawai'i Volcanoes National Park

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    Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.Prior to this study, the alien plant control program at Hawai'i Volcanoes National Park was hampered by the paucity and quality of alien plant distribution maps. A systematic program to map important localized alien plants was conducted 1983-1985 to determine the need and feasibility of controlling key alien plant species, establish a baseline for assessing the spread of these species, infer range expansions, locate all populations of a target species to assure thorough treatment, and assess the effectiveness of control programs. Thirty-six species were mapped, with emphasis given to localized alien plant species and those listed as target species in the 1982 Resources Management Plan (National Park Service 1982). The studies focused on Ainahou Ranch, Kilauea Crater, and the Coastal Lowlands west of the 1%9-1974 Mauna Ulu flows. The species distributions were mapped on topographic maps at 1:24,000, 1:12,000, or 1:6,000 scales, although most species are displayed in this report on smaller scale maps. In addition, species profiles are provided. These characterize importance to management, significance as a pest in native ecosystems, effective treatment methods, and history of management. There were two important findings from the distribution studies. Eleven species, previously not targeted for management, were identified from mapping efforts to be invasive and require control efforts. These are Formosan koa, slash pine, loquat, sisal, orange pittosporum, oleaster, English ivy, paperbark, blackwood acacia, kudzu, and guavasteen. The second finding is that five target species were found to be much more widespread than previously thought. These include silky oak, koa haole, fountain grass, Russian olive, and raspberry. This finding lead to an approach in which control efforts on widespread species were carried out only in intensive management units called Special Ecological Areas. Additional distribution mapping studies are recommended for widespread species.National Park Service Contract No. CA 8004 2 000

    Control of bacterial nitrate assimilation by stabilization of G-quadruplex DNA

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    Here we present a chemical-biology study in the model soil bacterium Paracoccus denitrificans, where we show ligand-specific control of nitrate assimilation. Stabilization of a G-quadruplex in the promoter region of the nas genes, encoding the assimilatory nitrate/nitrite reductase system, is achieved using known quadruplex ligands and results in attenuation of gene transcription

    The SLAC high‐density 3He target polarized by spin‐exchange optical plumbing

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    A new high‐density 3He target polarized by spin exchange with optically pumped rubidium vapor has recently been used at the Stanford Linear Accelerator in an experiment to measure the longitudinal spin‐dependent structure function of the neutron. The 3He target operated at a density of 2.3×1020 atoms/cm3 in a 30 cm long scattering region with polarizations between 30% and 40% measured with NMR techniques. Target cells with several day spin‐relaxation times were developed in order to achieve these polarizations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87509/2/244_1.pd

    The Lick AGN Monitoring Project: Photometric Light Curves and Optical Variability Characteristics

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    The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies selected to have black holes with masses roughly in the range 10^6-10^7 solar masses, as well as the well-studied AGN NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broad-band B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76-m Katzman Automatic Imaging Telescope (KAIT), the 2-m Multicolor Active Galactic Nuclei Monitoring (MAGNUM) telescope, the Palomar 60-in (1.5-m) telescope, and the 0.80-m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the photometric measurements, and present the AGN continuum light curves. We measure various variability characteristics of each of the light curves. We do not detect any evidence for a time lag between the B- and V-band variations, and we do not find significant color variations for the AGNs in our sample.Comment: 16 pages, 20 figures, 8 tables, accepted for publication in ApJ
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