8,939 research outputs found

    Enhancing efficiency of single, large-aperture antennas

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    Numerical analysis method provides means of describing energy distribution in focal plane of parabolic surface in terms of phase and wavelength. Two approaches for enhancing antenna efficiency include single, large reflector focused to feeding element, and array of smaller apertures whose individual outputs are summed

    Resolving the structure of TiBe12_{12}

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    There has been considerable controversy regarding the structure of TiBe12_{12}, which is variously reported as hexagonal and tetragonal. Lattice dynamics simulations based on density functional theory show the tetragonal phase space group I4/mmmI4/mmm to be more stable over all temperatures, while the hexagonal phase exhibits an imaginary phonon mode, which, if followed, would lead to the cell adopting the tetragonal structure. We then report the predicted ground state elastic constants and temperature dependence of the bulk modulus and thermal expansion for the tetragonal phase.Comment: In press at Acta Crystallographica B. Supplementary material appende

    Ethnic identity and aspirations among rural Alaska youth

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    The villages of rural Alaska comprise one of the most exceptional, yet least visible, sociocultural environments in the United States They are geographically remote, and set off from the mainstream also by their unique Eskimo, Indian or Aleut cultures. At the same time many economic, legal and cultural connections pull these villages toward the dominant U.S. society, impelling continual and rapid social change. Our research focuses on adolescents growing up in this culturally complex and changing environment. We employ survey data from adolescents in 19 rural schools to explore relationships between ethnic identity and students\u27 expectations about moving away or attending college. Many students describe their ethnic identity as mixed, both Native and non-Native. On some key variables, the responses of mixed-identity students fall between those of Natives and non-Natives, supporting a theoretical conception of ethnicity as a matter of degree rather than category. Migration and college expectations vary with ethnic identity, but the college expectations/identity relationship fades when we adjust for other variables. Ethnicity affects expectations for the most part indirectly, through ā€œcultural tool kitā€ variables including family role models and support. Gender differences in expectations, on the other hand, remain substantial even after adjusting for other variables

    General Clarkā€”"Hannibal of the West"

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    The influence of a transformative elementary science curriculum on at-risk students: A case report

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    This study explored the influence of a transformative elementary science curriculum on at-risk students. Project S.M.I.L.E., the focus of this study, uses strategies for curriculum development proposed by theorists of the post-modern era within the framework of social constructivism. Students in this program collaborate in their roles as students-as-teachers to prepare and present lessons to visitors of their school\u27s natural history museum and science laboratory; Data collection was conducted at Alison Leigh Elementary School in a metropolitan area of the southwestern United States. Observations of the students, interviews with parents and classroom teachers, student discussions, and journal writings of the 17 fifth grade S.M.I.L.E. team students were collected for data analysis in this case study. Five themes emerged from the data that conceptualized the influence of a transformative elementary science curriculum on at-risk students. Implications for transformative curriculum development were drawn

    Letter from Luther M. Grimes, Class of 1893 (1957)

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    Upon receiving an invitation to attend the 1957 dedication festivities for the newly built law building, Class of 1893 alum Luther M. Grimes hand wrote a response that is one part RSVP and one part trip down memory lane. He said that he was regretfully unable to attend; at 87 1/2 years it was on account of age that he couldn\u27t travel from his Iowa home. He considered that he may have been among the oldest living Indiana University alums, and was, with certainty, the last surviving member of his law class. As a Bloomington native with familial ties to the area, his memories included tending cows on a pasture that would later be sold to the university and become an athletic field. He and his father both considered Professor (and eventual dean) William Perry Rogers to be a personal friend. This relationship would prove critical during Grimes\u27 years as a law student - it was at his pleading that Rogers reconsidered a threat to resign after classroom hijinks involving a dog hidden in a desk during a lecture. This letter was warmly received and a press release and newspaper articles relaying its sentiments were published. Please see the comments sections for links to these materials

    Electrically-Small Low Q Radiator Structure and Method of Producing EM Waves Therewith

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    An electrically small radiator structure for radiating electromagnetic waves having an electrical size, k*a, with a value less than Ļ€/2 and above Ļ€/20,000 and configured to have at least a first and second magnetic, or electric, dipole element. Dipole elements are preferably oriented such that a source-associated standing energy value for the structure, or Wds(tR), is low, Radiative Q value preferably less than ā…“(k*a)3; and each of the elements, whether paired with respective electric dipole elements, is in electrical communication through a feed circuit to at least one power source. Further, a first dipole pair (or element) oriented orthogonally with respect to a second pair (or element) are in voltage phase-quadrature; the structure is operational at a frequency below 5 GHz; and dipole moments oriented such that the following is generally satisfied: a divergence of the Poynting vector of the pairs with respect to retarded time, namely āˆ‡|t R Ā·N, has a value less than 1.0. Also, a method of producing electromagnetic waves using an electrically small radiator structure, including configuring the structure to have at least a first and second pair of dipole moments and an electrical size, k*a, with a value less than Ļ€/2 and above Ļ€/20,000; and powering a first feed area of the first pair and a second feed area of the second pair with at least one source operating at a frequency to radiate the waves
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