299 research outputs found

    Telerobotic Space Station Applications

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    This paper presents telerobotic space station applications, important issues in telerobotics and work at the University of Alabama in Huntsville in the area of telerobotics

    03. Population Demographics of the Loggerhead Shrike: Insights into the Species Decline from a Long-Term Study in the Midewin National Tallgrass Prairie

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    We monitored a breeding population of loggerhead shrikes (Lanius ludovicianus) in the Midewin National Tallgrass Prairie from 2005 to 2016. Demographic data were compiled annually, including information on population size, age structure, and reproductive success. We banded adult shrikes, with some additional effort focused on nestlings (2005–2007) and independent hatch-year birds (2014–2016). We measured return rate as the number of birds that were previously banded. Site reuse rates were quantified as the use of a breeding territory in multiple years. Site fidelity, the use of a site by the same male or female in consecutive years, and dispersal distance of banded birds from their natal or previous breeding territory were assessed in 2015 and 2016, after inception of a color-banding program in 2014. Population size ranged from 4 to 14 breeding pairs, with additional single nonbreeding birds noted in most years. The percentage of the population that successfully fledged at least one young each year ranged from 50 to 100%. First nests were more often unsuccessful than later nests. Site reuse was high, and appears related to nesting success in the preceding year, suggesting that shrikes use postbreeding information when selecting nest sites. The ratio of second-year (SY, first year breeder) to after-second-year (ASY) birds varied by year and among sex, with largerthan- expected numbers of SY female birds. Average natal dispersal distance within Midewin was 0.97 km, and average adult dispersal distance was 1.6 km. Female dispersal distance was slightly greater than that of males (2.1 km vs. 1.3 km). By the end of each breeding season, the majority of the known adult population was banded, but approximately only one-third of the banded population returns at the start of the subsequent breeding season. Population size and trend appear correlated with number of ASY birds, and immigration rates of unbanded birds include first-year breeders and those that have bred at least once before, likely from outside of Midewin

    Gold(I)-Catalysed Direct Thioetherifications Using Allylic Alcohols: an Experimental and Computational Study

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    A gold(I)-catalysed direct thioetherification reaction between allylic alcohols and thiols is presented. The reaction is generally highly regioselective (S(N)2′). This dehydrative allylation procedure is very mild and atom economical, producing only water as the by-product and avoiding any unnecessary waste/steps associated with installing a leaving or activating group on the substrate. Computational studies are presented to gain insight into the mechanism of the reaction. Calculations indicate that the regioselectivity is under equilibrium control and is ultimately dictated by the thermodynamic stability of the products

    Analysis of electromagnetic interference from power system processing and transmission components for Space Station Freedom

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    The goal of this research project was to analyze the potential effects of electromagnetic interference (EMI) originating from power system processing and transmission components for Space Station Freedom. The approach consists of four steps: (1) developing analytical tools (models and computer programs); (2) conducting parameterization (what if?) studies; (3) predicting the global space station EMI environment; and (4) providing a basis for modification of EMI standards

    Irradiation study of a fully monolithic HV-CMOS pixel sensor design in AMS 180 nm

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    High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) based on the 180 nm HV-CMOS process have been proposed to realize thin, fast and highly integrated pixel sensors. The MuPix7 prototype, fabricated in the commercial AMS H18 process, features a fully integrated on-chip readout, i.e. hit-digitization, zero suppression and data serialization. It is the first fully monolithic HV-CMOS pixel sensor that has been tested for the use in high irradiation environments like HL-LHC. We present results from laboratory and test beam measurements of MuPix7 prototypes irradiated with neutrons (up to 5.0⋅1015 neq/cm25.0\cdot10^{15}{\,\rm{n}_{\rm{eq}}/cm^2}) and protons (up to 7.8⋅1015 protons/cm27.8\cdot 10^{15} \,\rm{protons}/cm^2) and compare the performance with non-irradiated sensors. Efficiencies well above 90 % at noise rates below 200 Hz per pixel are measured. A time resolution better than 22 ns is measured for all tested settings and sensors, even at the highest irradiation fluences. The data transmission at 1.25 Gbit/s and the on-chip PLL remain fully functional

    Conservation of grassland birds in North America: understanding ecological processes in different regions

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    Many species of birds that depend on grassland or savanna habitats have shown substantial overall population declines in North America. To understand the causes of these declines, we examined the habitat requirements of birds in six types of grassland in different regions of the continent. Open habitats were originally maintained by ecological drivers (continual and pervasive ecological processes) such as drought, grazing, and fire in tallgrass prairie, mixed-grass prairie, shortgrass prairie, desert grassland, and longleaf pine savanna. By contrast, grasslands were created by occasional disturbances (e.g., fires or beaver [Castor canadensis] activity) in much of northeastern North America. The relative importance of particular drivers or disturbances differed among regions. Keystone mammal species grazers such as prairie-dogs (Cynomys spp.) and bison (Bison bison) in western prairies, and dam-building beavers in eastern regions of the continent. Deciduous forests played a crucial, and frequently unappreciated, role in maintaining many grassland systems. Although fire was important in preventing invasion of woody plants in the tallgrass and moist mixed prairies, grazing played a more important role in maintaining the typical grassland vegetation of shortgrass prairies and desert grasslands. Heavy grazing by prairiedogs or bison created a low \u27grazing lawn\u27 that is the preferred habitat for many grassland bird species that are restricted to the shortgrass prairie and desert grasslands. Ultimately, many species of grassland birds are vulnerable because people destroyed their breeding, migratory, and wintering habitat, either directly by converting it to farmland and building lots, or indirectly by modifying grazing patterns, suppressing fires, or interfering with other ecological processes that originally sustained open grassland. Understanding the ecological processes that originally maintained grassland systems is critically important for efforts to improve, restore, or create habitat for grassland birds and other grassland organisms. Consequently, preservation of large areas of natural or seminatural grassland, where these processes can be studied and core populations of grassland birds can flourish, should be a high priority. However, some grassland birds now primarily depend on artificial habitats that are managed to maximize production of livestock, timber, or other products. With a sound understanding of the habitat requirements of grassland birds and the processes that originally shaped their habitats, it should be possible to manage populations sustainably on \u27working land\u27 such as cattle ranches, farms, and pine plantations. Proper management of private land will be critical for preserving adequate breeding, migratory, and winter habitat for grassland and savanna species

    Upgrading the beam telescopes at the DESY II Test Beam Facility

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    The DESY II Test Beam Facility is a key infrastructure for modern high energy physics detector development, providing particles with a small momentum spread in a range from 1 to 6 GeV to user groups e.g. from the LHC experiments and Belle II as well as generic detector R&D. Beam telescopes are provided in all three test beam areas as precise tracking reference without time stamping, with triggered readout and a readout time of >115 μ\mus . If the highest available rates are used, multiple particles are traversing the telescopes within one readout frame, thus creating ambiguities that cannot be resolved without additional timing layers. Several upgrades are currently investigated and tested: Firstly, a fast monolithic pixel sensor, the TelePix, to provide precise track timing and triggering on a region of interest is proposed to overcome this limitation. The TelePix is a 180 nm HV-CMOS sensor that has been developed jointly by DESY, KIT and the University of Heidelberg and designed at KIT. In this publication, the performance evaluation is presented: The difference between two amplifier designs is evaluated. A high hit detection efficiency of above 99.9 % combined with a time resolution of below 4 ns at negligible pixel noise rates is determined. Finally, the digital hit output to provide region of interest triggering is evaluated and shows a short absolute delay with respect to a traditional trigger scintillator as well as an excellent time resolution. Secondly, a fast LGAD plane has been proposed to provide a time resolution of a few 10 ps, which is foreseen to drastically improve the timing performance of the telescope. Time resolutions of below 70 ps have been determined in collaboration with the University of California, Santa Barbara
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