876 research outputs found
Space and energy conservation housing prototype unit development
Construction plans are discussed for a house which will demonstrate the application of advanced technology to minimize energy requirements and to help direct further development in home construction by defining the interaction of integrated energy and water systems with building configuration and construction materials. Housing unit designs are provided and procedures for the analysis of a variety of housing strategies are developed
Handling Attrition in Longitudinal Studies: The Case for Refreshment Samples
Panel studies typically suffer from attrition, which reduces sample size and
can result in biased inferences. It is impossible to know whether or not the
attrition causes bias from the observed panel data alone. Refreshment samples -
new, randomly sampled respondents given the questionnaire at the same time as a
subsequent wave of the panel - offer information that can be used to diagnose
and adjust for bias due to attrition. We review and bolster the case for the
use of refreshment samples in panel studies. We include examples of both a
fully Bayesian approach for analyzing the concatenated panel and refreshment
data, and a multiple imputation approach for analyzing only the original panel.
For the latter, we document a positive bias in the usual multiple imputation
variance estimator. We present models appropriate for three waves and two
refreshment samples, including nonterminal attrition. We illustrate the
three-wave analysis using the 2007-2008 Associated Press-Yahoo! News Election
Poll.Comment: Published in at http://dx.doi.org/10.1214/13-STS414 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
How preregistration can help increase youth voter turnout
In the 2014 midterm elections, less than a quarter of those aged 18-29 voted, half the number of those who did who were aged 45-64. How can this poor level of youth turnout be addressed? In new research, John B. Holbein & D. Sunshine Hillygus examine the effects of preregistration laws in states like California and Florida, which allow those who are 16 or 17 to register before they are eligible to vote. By comparing the rates of those who preregister to vote with those who register traditionally, they find that preregistration can increase turnout by up to 13 percent, and that this effect is consistent for both Republicans and Democrats
The Evolving Activity of the Dynamically Young Comet C/2009 P1 (Garradd)
We used the UltraViolet-Optical Telescope on board Swift to observe the
dynamically young comet C/2009 P1 (Garradd) from a heliocentric distance of 3.5
AU pre-perihelion until 4.0 AU outbound. At 3.5 AU pre-perihelion, comet
Garradd had one of the highest dust-to-gas ratios ever observed, matched only
by comet Hale-Bopp. The evolving morphology of the dust in its coma suggests an
outburst that ended around 2.2 AU pre-perihelion. Comparing slit-based
measurements and observations acquired with larger fields of view indicated
that between 3 AU and 2 AU pre-perihelion a significant extended source started
producing water in the coma. We demonstrate that this source, which could be
due to icy grains, disappeared quickly around perihelion. Water production by
the nucleus may be attributed to a constantly active source of at least 75
km, estimated to be more than 20 percent of the surface. Based on our
measurements, the comet lost kg of ice and dust during this
apparition, corresponding to at most a few meters of its surface.Even though
this was likely not Garradd's first passage through the inner solar system, the
activity of the comet was complex and changed significantly during the time it
was observed
Repeat Purchase intentions: Exploring the perceived values of Locally-made Hand-Woven Bags in Lagawe, Ifugao, Philippines
Purpose: Purchase behavior is a significant consideration for consumers when choosing and evaluating various products. Perceived values influencing repurchase intention are critical since these are the major inputs used by marketing managers to estimate future extra sales and develop strategies to influence consumers' repurchasing behavior. As a result, this study studied the perceived value of locally-made hand-woven bags and the repurchase intentions of consumers in Ifugao, Philippines, which also serves as the foundation for offering interventions to raise the possibility of purchasing a local product.
Design/methodology/approach: The quantitative research method's descriptive-correlational research design with the use of a validated survey instrument was utilized to gather data from 202 real buyers and users of Ifugao weave bags in the three municipalities of Ifugao, namely Kiangan, Hingyon, and Lagawe. Using SPSS, data was counted, handled, and analyzed using mean, standard deviation, and Pearson-r correlation.
Findings: The findings demonstrated that local weave bags have functional, experiential, cultural, aesthetics, and social values, which all influence their repurchase intention. All of the characteristics observed had a moderate to a high relationship with repurchase intent.
Practical Implications: Nonetheless, marketing methods to develop Ifugao weave bags in the Philippines that integrate these criteria may have a high likelihood of success in retaining existing customers and attracting new markets
Ab Initio Calculation of Impurity Effects in Copper Oxide Materials
We describe a method for calculating, within density functional theory, the
electronic structure associated with typical defects which substitute for Cu in
the CuO2 planes of high-Tc superconducting materials. The focus is primarily on
Bi2Sr2CaCu2O8, the material on which most STM measurements of impurity
resonances in the superconducting state have been performed. The magnitudes of
the effective potentials found for Zn, Ni and vacancies on the in-plane Cu
sites in this host material are remarkably consistent with phenomenological
fits of potential scattering models to STM resonance energies. The effective
potential ranges are quite short, of order 1 A with weak long range tails, in
contrast to some current models of extended potentials which attempt to fit STM
data. For the case of Zn and Cu vacancies, the effective potentials are
strongly repulsive, and states on the impurity site near the Fermi level are
simply removed. The local density of states (LDOS) just above the impurity is
nevertheless found to be a maximum in the case of Zn and a local minimum in
case of the vacancy, in agreement with experiment. The Zn and Cu vacancy
patterns are explained as due to the long-range tails of the effective impurity
potential at the sample surface. The case of Ni is richer due to the Ni atom's
strong hybridization with states near the Fermi level; in particular, the short
range part of the potential is attractive, and the LDOS is found to vary
rapidly with distance from the surface and from the impurity site. We propose
that the current controversy surrounding the observed STM patterns can be
resolved by properly accounting for the effective impurity potentials and
wave-functions near the cuprate surface. Other aspects of the impurity states
for all three species are discussed.Comment: 37 pp. pdf including figures, submitted to Phys. Rev.
A fully 3-dimensional thermal model of a comet nucleus
A 3-D numerical model of comet nuclei is presented. An implicit numerical
scheme was developed for the thermal evolution of a spherical nucleus composed
of a mixture of ice and dust. The model was tested against analytical
solutions, simplified numerical solutions, and 1-D thermal evolution codes. The
3-D code was applied to comet 67P/Churyumov-Gerasimenko; surface temperature
maps and the internal thermal structure was obtained as function of depth,
longitude and hour angle. The effect of the spin axis tilt on the surface
temperature distribution was studied in detail. It was found that for small
tilt angles, relatively low temperatures may prevail on near-pole areas,
despite lateral heat conduction. A high-resolution run for a comet model of
67P/Churyumov-Gerasimenko with low tilt angle, allowing for crystallization of
amorphous ice, showed that the amorphous/crystalline ice boundary varies
significantly with depth as a function of cometary latitude.Comment: 19 pages, 10 figure
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