132 research outputs found
ASSESSING SUSTAINABILITY FOR PACKAGING: ENVIRONMENTAL CHALLENGES AND RESPONSIBILITIES OF PACKAGING DESIGN
Packaging is a unique industry and often not top of mind to everyday people. However, it plays an important role influencing consumers with every purchasing decision in addition to having major impacts on the environment and climate change. In this study the use of assessment tools was examined to identify environmental impacts of packaging and how sustainable packaging design provided solutions to those impacts. Several research questions were identified and addressed regarding media influence, specific environmental impact indicators, existing assessment tools such as life cycle assessments, and a policy evaluation for producer responsibility. An extensive literature review was conducted regarding the four research topics to provide findings on flexible packaging, one of more visible packaging types to everyday consumers that represent environmental challenges. A fifteen-question online survey was sent to twenty experts in the packaging field to gain their insights on the four major topics. The results of the survey and analysis were compared to the literature review findings to answer the overall research question. Media influence does occur amongst consumers as well as the expert decision makers on the issue of packaging impacts especially regarding recyclability. Assessment tools for packaging were effective at addressing the harmful environmental and climate impacts of packaging. These tools helped to highlight sustainable packaging development and design solutions, in addition to better communicate these findings to the public. Finally, the responsibility of packaging impacts was debated, however Extended Producer Responsibility programs were implemented in several states in the US where the success of that tactic is not yet determined. Addressing these research problems on packaging will help consumers understand a piece of the environmental equation that affects their everyday lives that is not communicated fully enough to the public
Quantum Hydrodynamic Model for the enhanced moments of Inertia of molecules in Helium Nanodroplets: Application to SF
The increase in moment of inertia of SF in helium nanodroplets is
calculated using the quantum hydrodynamic approach. This required an extension
of the numerical solution to the hydrodynamic equation to three explicit
dimensions. Based upon an expansion of the density in terms of the lowest four
Octahedral spherical harmonics, the predicted increase in moment of inertia is
, compared to an experimentally determined value of , i.e., 55% of the observed value. The difference is likely in at
least part due to lack of convergence with respect to the angular expansion,
but at present we do not have access to the full densities from which a higher
order expansion can be determined. The present results contradict those of Kwon
et al., J. Chem. Phys. {\bf 113}, 6469 (2000), who predicted that the
hydrodynamic theory predicted less than 10% of the observed increase in moment
of inertia.Comment: 10 pages, including 1 figur
"Valuing Beach Closures on the Padre Island National Seashore"
In this paper we estimate the economic loss of hypothetical beach closures on the Padre Island National Seashore on the Gulf Coast of Texas. We use a travel cost random utility maximization (RUM) model with data from a random phone survey of Texas residents completed in 2001. We simulate realistic closures that may occur in event of an oil spill or other disruption. For comparison we valued the loss of beach closures in the heavily populated Galveston area. The aggregate losses on Padre Island were highest on weekend days in July estimated at ). They were lowest on weekdays in September at 28. A similar closure of beaches near Galveston resulted in losses of 852,000 (weekend day) with a per trip loss of $30.random utility model, beach use, non-market valuation
The Pathwise Classroom Orientation System: A Teacher Mentoring Model That Really Works
Mentoring beginning teachers in the United States is on the rise due to the alarming attrition rates of recent decades. There is a greater need to attract/retain teachers in suburban, urban and areas of poverty
Rotation in liquid He: Lessons from a toy model
This paper presents an analysis of a model problem, consisting of two
interacting rigid rings, for the rotation of molecules in liquid He. Due to
Bose symmetry, the excitation of the rotor corresponding to a ring of N helium
atoms is restricted to states with integer multiples of N quanta of angular
momentum. This minimal model shares many of the same features of the rotational
spectra that have been observed for molecules in nanodroplets of helium atoms. In particular, this model predicts, for the first time,
the very large enhancement of the centrifugal distortion constants that have
been observed experimentally. It also illustrates the different effects of
increasing rotational velocity by increases in angular momentum quantum number
or by increasing the rotational constant of the molecular rotor. It is found
that fixed node, diffusion Monte Carlo and a hydrodynamic model provide upper
and lower bounds on the size of the effective rotational constant of the
molecular rotor when coupled to the helium
6DOF Testing of the SLS Inertial Navigation Unit
The Navigation System on the NASA Space Launch System (SLS) Block 1 vehicle performs initial alignment of the Inertial Navigation System (INS) navigation frame through gyrocompass alignment (GCA). Because the navigation architecture for the SLS Block 1 vehicle is a purely inertial system, the accuracy of the achieved orbit relative to mission requirements is very sensitive to initial alignment accuracy. The assessment of this sensitivity and many others via simulation is a part of the SLS Model-Based Design and Model-Based Requirements approach. As a part of the aforementioned, 6DOF Monte Carlo simulation is used in large part to develop and demonstrate verification of program requirements. To facilitate this and the GN&C flight software design process, an SLS-Program-controlled Design Math Model (DMM) of the SLS INS was developed by the SLS Navigation Team. The SLS INS model implements all of the key functions of the hardware-namely, GCA, inertial navigation, and FDIR (Fault Detection, Isolation, and Recovery)-in support of SLS GN&C design requirements verification. Despite the strong sensitivity to initial alignment, GCA accuracy requirements were not verified by test due to program cost and schedule constraints. Instead, the system relies upon assessments performed using the SLS INS model. In order to verify SLS program requirements by analysis, the SLS INS model is verified and validated against flight hardware. In lieu of direct testing of GCA accuracy in support of requirement verification, the SLS Navigation Team proposed and conducted an engineering test to, among other things, validate the GCA performance and overall behavior of the SLS INS model through comparison with test data. This paper will detail dynamic hardware testing of the SLS INS, conducted by the SLS Navigation Team at Marshall Space Flight Center's 6DOF Table Facility, in support of GCA performance characterization and INS model validation. A 6-DOF motion platform was used to produce 6DOF pad twist and sway dynamics while a simulated SLS flight computer communicated with the INS. Tests conducted include an evaluation of GCA algorithm robustness to increasingly dynamic pad environments, an examination of GCA algorithm stability and accuracy over long durations, and a long-duration static test to gather enough data for Allan Variance analysis. Test setup, execution, and data analysis will be discussed, including analysis performed in support of SLS INS model validation
Acoustic attenuation probe for fermion superfluidity in ultracold atom gases
Dilute gas Bose-Einstein condensates (BEC's), currently used to cool
fermionic atoms in atom traps, can also probe the superfluidity of these
fermions. The damping rate of BEC-acoustic excitations (phonon modes), measured
in the middle of the trap as a function of the phonon momentum, yields an
unambiguous signature of BCS-like superfluidity, provides a measurement of the
superfluid gap parameter and gives an estimate of the size of the Cooper-pairs
in the BEC-BCS crossover regime. We also predict kinks in the momentum
dependence of the damping rate which can reveal detailed information about the
fermion quasi-particle dispersion relation.Comment: 4 pages, 2 figures. Revised versio
S-pairing in neutron matter. I. Correlated Basis Function Theory
S-wave pairing in neutron matter is studied within an extension of correlated
basis function (CBF) theory to include the strong, short range spatial
correlations due to realistic nuclear forces and the pairing correlations of
the Bardeen, Cooper and Schrieffer (BCS) approach. The correlation operator
contains central as well as tensor components. The correlated BCS scheme of
Ref. [Nucl. Phys. A363 (1981) 383], developed for simple scalar correlations,
is generalized to this more realistic case. The energy of the correlated pair
condensed phase of neutron matter is evaluated at the two--body order of the
cluster expansion, but considering the one--body density and the corresponding
energy vertex corrections at the first order of the Power Series expansion.
Based on these approximations, we have derived a system of Euler equations for
the correlation factors and for the BCS amplitudes, resulting in correlated non
linear gap equations, formally close to the standard BCS ones. These equations
have been solved for the momentum independent part of several realistic
potentials (Reid, Argonne v_{14} and Argonne v_{8'}) to stress the role of the
tensor correlations and of the many--body effects. Simple Jastrow correlations
and/or the lack of the density corrections enhance the gap with respect to
uncorrelated BCS, whereas it is reduced according to the strength of the tensor
interaction and following the inclusion of many--body contributions.Comment: 20 pages, 8 figures, 1 tabl
Acoustic attenuation rate in the Fermi-Bose model with a finite-range fermion-fermion interaction
We study the acoustic attenuation rate in the Fermi-Bose model describing a
mixtures of bosonic and fermionic atom gases. We demonstrate the dramatic
change of the acoustic attenuation rate as the fermionic component is evolved
through the BEC-BCS crossover, in the context of a mean-field model applied to
a finite-range fermion-fermion interaction at zero temperature, such as
discussed previously by M.M. Parish et al. [Phys. Rev. B 71, 064513 (2005)] and
B. Mihaila et al. [Phys. Rev. Lett. 95, 090402 (2005)]. The shape of the
acoustic attenuation rate as a function of the boson energy represents a
signature for superfluidity in the fermionic component
6DOF Testing of the SLS Inertial Navigation Unit
The Navigation System on the NASA Space Launch System (SLS) Block 1 vehicle performs initial alignment of the Inertial Navigation System (INS) navigation frame through gyrocompass alignment (GCA). In lieu of direct testing of GCA accuracy in support of requirement verification, the SLS Navigation Team proposed and conducted an engineering test to, among other things, validate the GCA performance and overall behavior of the SLS INS model through comparison with test data. This paper will detail dynamic hardware testing of the SLS INS, conducted by the SLS Navigation Team at Marshall Space Flight Center's 6DOF Table Facility, in support of GCA performance characterization and INS model validation. A 6-DOF motion platform was used to produce 6DOF pad twist and sway dynamics while a simulated SLS flight computer communicated with the INS. Tests conducted include an evaluation of GCA algorithm robustness to increasingly dynamic pad environments, an examination of GCA algorithm stability and accuracy over long durations, and a long-duration static test to gather enough data for Allan Variance analysis. Test setup, execution, and data analysis will be discussed, including analysis performed in support of SLS INS model validation
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