2,780 research outputs found
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Dynamic behavior and damping capacity of auxetic foam pads
A novel set of auxetic (negative Poisson's ratio) open cell polyurethane foam has been developed and tested under dynamic
loading conditions to assess the viscoelastic response under white noise random excitation and compressive cycling. Foam pads
normalized to standard ISO 13753 have been tested at room temperature and frequency bandwidth 10-500 Hz to assess
transmissibility characteristics for possible antivibration glove applications. The results show that the ISO 13753 normalized
transmissibility for these foams falls below 0.6 above 100 Hz, with lower peak maximum stresses under indentation compared to
conventional open cell solids. These results suggest possible use of the auxetic foam for pads or linens against « white fingers«
vibration applications. Further tests have been conducted on cyclic compressive loading up to 3 Hz and loading ratios of 0.95 for
loading histories up to 100000 cycles. The damping capacity of the auxetic foams showed and increase by a factor 10 compared
to the conventional foams used to manufacture the negative Poisson's ratio ones, and stiffness degradation stabilized after few tens on cycles
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Mechanical performance of auxetic polyurethane foam for antivibration glove applications
In this study the static and dynamic characteristics of conventional open cell
polyurethane (PU), of auxetic (negative Poissonâs ratio) and of iso-density foams
were analysed. The specimens were produced from conventional gray open-cells
polyurethane foam with 30-35 pores/inch and 0.0027 g/cm3 density, by means of
process which has been previously defined by the authors. Poissonâs ratio
measurements were performed under quasi-static conditions using an MTS 858 servohydraulic
test machine and a video image acquisition system. For the auxetic foams
the results suggested similar behaviour to that previously reported in the literature,
with significant increases in stiffness during compressive loading, and a significant
dependence of the Poissonâs ratio on the applied strain. Transmissibility tests,
performed in accordance with the ISO 13753 procedure for antivibration glove
materials, suggested a strong dependence of the transmissibility on the foam
manufacturing parameters. Within the frequency range from 10 to 31.5 Hz the
transmissibility was found to be greater than 1, while it was less than 1 at all
frequencies greater than 31.5 Hz. The transmissibility results were similar to the mean
values for 80 resilient materials tested by Koton et. al., but were higher than the five
best materials (not all polymeric) identified by the same researchers. In this study it
has been suggested that the resilient behaviour of glove isolation materials should also
be evaluated in terms of the indentation characteristics. A simple, linear elastic, Finite
Element simulation was therefore performed, and the indentation results suggested
that auxetic foams offer a significant decrease in compressive stresses with respect to
conventional PU foams
Farm Animal Welfare, Consumer Willingness to Pay, and Trust: Results of a Cross-National Survey
Higher animal welfare standards increase costs along the supply chain of certified animal-friendly products (AFP). Since the market outcome of certified AFP depends on consumer confidence toward supply chain operators complying with these standards, the role of trust in consumer willingness-to-pay (WTP) for AFP is paramount. Results from a contingent valuation survey administered in five European Union countries show that WTP estimates were sensitive to robust measures of consumer trust for certified AFP. Deriving the WTP effect of a single food category on total food expenditure is difficult for survey respondents; hence, a budget approach was employed to facilitate this process.Animal welfare, certification, consumer trust, WTP, budget approach, Crop Production/Industries, Environmental Economics and Policy, Farm Management, Livestock Production/Industries, C81, Q13, Q18,
Solutions to Donaldson's hyperkaehler reduction on a curve
We study an infinite-dimensional hyperk\ue4hler reduction introduced by Donaldson and associated with the constant scalar curvature equation on a Riemann surface. It is known that the corresponding moment map equations admit special solutions constructed from holomorphic quadratic differentials. Here we obtain a more general existence result and so a larger hyperk\ue4hler moduli space
Reclassification of the nearest quasar pair candidate: SDSS J15244+3032 - RXS J15244+3032
We present optical spectroscopy of the nearest quasar pair listed in the 13th
edition of the Veron-Cetty & Veron catalogue, i.e. the two quasars SDSS
J15244+3032 and RXS J15244+3032 (redshift z~0.27, angular separation ~7 arcsec,
and line-of-sight velocity difference ~1900 km/s). This system would be an
optimal candidate to investigate the mutual interaction of the host galaxies
with ground based optical imaging and spectroscopy. However, new optical data
demonstrate that RXS J15244+3032 is indeed a star of spectral type G.
This paper includes data gathered with the Asiago 1.82m telescope (Cima Ekar
Observatory, Asiago, Italy).Comment: 5 pages, 2 figures, 1 table. Accepted for publication in APS
HST Observations of the Optical Jets of PKS 0521-365, 3C371, and PKS 2201+044
HST observations have led to the discovery of the optical counterpart of the
radio jet of PKS 2201+044, and to a detailed analysis of the optical jets of
PKS 0521-365 and 3C371. At HST spatial resolution these jets are well resolved,
displaying knotty morphologies. When compared with radio maps of appropriate
resolution, a clear one-to-one correspondence between optical and radio
structures is found, showing that all detected optical structures are indeed
related to the radio synchrotron emission. Photometry of the brightest knots
shows that the radio-to-optical spectral index and the derived intensity of the
equipartition magnetic field are approximately constant along the jet. Thus,
present observations suggest that the electron energy distribution does not
change significantly all along the jet.Comment: Accepted for publications on the Astrphysical Journal. Contains 14
pages and 5 figure
Estimating the willingness to pay for Warmer and Drier Homes.
New Zealand is one of several countries to use subsidies for retrofitting insulation and installing improved heating devices such as heat pumps. The valuation of these devices by the affected populations remains unknown. We investigate willingness to pay for such devices, using a choice experiment with a sample of Pacific Islanders in the upper North Island. This is a high-risk group for respiratory disease, who typically rent crowded and inadequately heated dwellings. Using both conditional logit and panel mixed logit models, we find reasonably precise estimates of the willingness to pay for four improved heating and humidity control devices, which would cover the capital costs of two of the devices, and about three-quarters of the cost of the other two devices
Choice set formation for outdoor destinations: the role of motivations and preference discrimination in site selection for the management of public expenditures on protected areas
Effective public expenditure currently dominates the management focus of many protected areas. This calls for explicit modeling of constraints and motivations that, respectively, obstruct and stimulate visits to selected outdoor destinations. Choice set formation is the result of screening and/or inclusion of specific sites (alternatives) to form the set of sites considered in real choices. Evidence shows that the omission of a structural representation of choice set formation is harmful to econometric inference. Yet, the literature has largely ignored the underlying behavioral phenomenon. We show, using a discrete choice experiment involving selection among seven recreational sites in an Italian national park, that choice set formation is behaviorally relevant, even after controlling for preference discrimination. Motivations (why visit?) are important determinants of preliminary site screening for choice set inclusion, as well as site selection, justifying the additional value of such modeling extension
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