1,505 research outputs found
Public knowledge about polar regions increases while concerns remain unchanged
The authors of this brief conduct the first comparative analysis of the polar questions that were part of the National Opinion Research Center\u27s 2006 and 2010 General Social Survey. Developed by scientists at the National Science Foundation\u27s Office of Polar Programs, these questions covered topics such as climate change, melting ice and rising sea levels, and species extinction. The authors report that the public\u27s knowledge about the north and south polar regions significantly improved between 2006 and 2010--before and after the International Polar Year. In addition, respondents who know more about science in general, and polar facts specifically, tend to be more concerned about polar changes. More knowledgeable respondents also tend to favor reserving the Antarctic for science, rather than opening it for commercial development
Evaluation of Hybrid-III 6YO ATD chest jacket shape and position
In previous work, belt fit on the Hybrid-III six-year-old (6YO) anthropomorphic test device (ATD) was found to depend on the positioning of the chest jacket of the ATD. Moreover, differences were noted between jackets manufactured by Denton-ATD and First Technology Safety Systems (FTSS). The objective of this study was to quantify differences between the manufacturers’ jackets by detailed measurements of exemplar jackets and to assess the effects of jacket installation procedure on jacket position.
A custom fixture was designed to hold rigidly the thorax, pelvis, and head of a 6YO ATD while allowing the chest jacket to be installed and removed. Testing was conducted with two jackets from FTSS and one from Denton. In pilot testing, jacket position was affected by the installation procedure and by the initial position of the shoulder components. Detailed measurements were made using a portable surface measurement device (laser
scanner) with each jacket in six conditions defined by initial shoulder position and the manner in which the jacket was installed. Quantitative comparisons in jacket position and shape were conducted in software using the laserscan data. Notable differences in jacket shape were observed between the FTSS and Denton jackets, with the FTSS jacket having a wider, flatter profile in the lateral shoulder area and the Denton jacket extending more forward in the upper chest area. However, the effects of jacket positioning were much larger than differences between manufacturers in jacket shape. Pulling the jacket down firmly resulted in jacket shoulder positions relative to the spine differing by more than 25 mm from those obtained by pulling the jacket down lightly, with results dependent on the initial positions of the shoulder components.
The results of this study indicate that careful attention to jacket positioning is needed to obtain a consistent relationship between the chest and shoulder surfaces and the ATD skeleton. Pulling the jacket down firmly after initially placing the shoulder components in a downward/rearward position is suggested. Monitoring and adjusting the location of reference points on the jacket relative to specified hard points on the ATD skeletonprovides a means for ensuring that the jacket is consistently placed for static or dynamic testing.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89865/1/102811.pd
Effects of obesity on seat belt fit
Obesity has been shown to increase the risk of some types of injury in crashes. One hypothesis is that obesity adversely effects belt fit by changing the routing of the belt relative to the underlying skeletal structures. To evaluate this hypothesis, belt fit was measured in a laboratory study of 54 men and women, 48 percent of whom
were obese, with a body mass index (BMI) of 30 kg/m2 or greater. Test conditions included a wide range of upper and lower belt anchorage locations and ranges of seat height, seat cushion angle, and seat back angle spanning a large fraction of current vehicle front and rear seats. In some conditions, foot position was restricted
to simulate the typical situation in the second row of a small sedan. Across individuals, an increase in BMI of
10-kg/m2 was associated with a lap belt positioned 43 mm further forward and 21 mm higher relative to the anterior-superior iliac spines of the pelvis. Each 10-kg/m2 increase in BMI was associated with an increase in lap belt webbing length of 130 mm. The worsening of lap belt fit with restricted foot position was slightly greater
for obese participants. Obesity was associated with a more-inboard shoulder belt routing across a wide range of upper belt anchorage locations, and the shoulder belt webbing length between the D-ring and latchplate increased by an average of 60 mm with each 10-kg/m2 increase in BMI. The results suggest that obesity effectively
introduces slack in the seat belt system by routing the belt further away from the skeleton. Particularly in frontal
crashes, but also in rollovers and other scenarios, this slack will result in increased excursions and an increased
likelihood and severity of contacts with the interior. The higher routing of the lap belt with respect to the pelvis also increases the likelihood of submarining in frontal crashes.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89867/1/102813.pd
Improving the repeatability and reproducibility of belt fit measurement with 6YO and 10YO ATDs
In previous work, researchers at the University of Michigan Transportation Research Institute (UMTRI) developed a method for quantifying the belt fit provided by belt-positioning boosters by measuring the belt location relative to the six- and ten-year-old Hybrid-III dummies. In another study, the torso and lap belt scores
obtained by this method were found to be closely related to the belt fit obtained by similar-size children across a wide range of booster and belt conditions. The Insurance Institute for Highway Safety (IIHS) adapted the UMTRI procedure to develop a rating system for booster belt fit, but adoption by other labs has been slowed by difficulty in obtaining repeatable results.
The current study was undertaken to improve the repeatability and reproducibility across operators of the procedure. The modifications made by IIHS were studied and most incorporated, and a number of other issues were examined through pilot testing. A revised version of the procedure was tested with repeated measurements
by three operators in six boosters. The results were analyzed to quantify the variance associated with the operators, the installation of the booster and dummy, and the routing of the belt.
The results show that trained operators can perform the procedure with minimal systematic bias across boosters.
The variability within booster varies considerably, with some boosters producing higher precision measurements due to the design of their belt-routing features. For any particular booster, the booster and dummy installation process accounts for about half the variability in the belt fit scores with the remainder due to variability in the belt routing and other measurement variability.
Based on these findings, multiple measurements of belt fit in each booster are recommended to establish the desired level of confidence in the true belt fit. Straightforward statistical methods involving confidence intervals are recommended for establishing objective test methods. More testing will be needed to determine the reproducibility of the method across laboratories.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89866/1/102812.pd
Finding the trigger to Iapetus' odd global albedo pattern: Dynamics of dust from Saturn's irregular satellites
The leading face of Saturn's moon Iapetus, Cassini Regio, has an albedo only
one tenth that on its trailing side. The origin of this enigmatic dichotomy has
been debated for over forty years, but with new data, a clearer picture is
emerging. Motivated by Cassini radar and imaging observations, we investigate
Soter's model of dark exogenous dust striking an originally brighter Iapetus by
modeling the dynamics of the dark dust from the ring of the exterior retrograde
satellite Phoebe under the relevant perturbations. In particular, we study the
particles' probabilities of striking Iapetus, as well as their expected spatial
distribution on the Iapetian surface. We find that, of the long-lived particles
(greater than about 5 microns), most particle sizes (greater than about 10
microns) are virtually certain to strike Iapetus, and their calculated
distribution on the surface matches up well with Cassini Regio's extent in its
longitudinal span. The satellite's polar regions are observed to be bright,
presumably because ice is deposited there. Thus, in the latitudinal direction
we estimate polar dust deposition rates to help constrain models of thermal
migration invoked to explain the bright poles (Spencer & Denk 2010). We also
analyze dust originating from other irregular outer moons, determining that a
significant fraction of that material will eventually coat Iapetus--perhaps
explaining why the spectrum of Iapetus' dark material differs somewhat from
that of Phoebe. Finally we track the dust particles that do not strike Iapetus,
and find that most land on Titan, with a smaller fraction hitting Hyperion. As
has been previously conjectured, such exogenous dust, coupled with Hyperion's
chaotic rotation, could produce Hyperion's roughly isotropic, moderate-albedo
surface.Comment: Accepted for publication in Icaru
Characterizing Child Head Motions Relative to Vehicle Rear Seat Compartment in Motor Vehicle Crashes
Technical Report FinalImproved padding or other countermeasures in vehicle rear compartments could reduce the incidence
of head trauma for child occupants. However, knowledge of likely child head impact locations for a
range of crash scenarios is needed to determine which areas and structures should be padded and
where a side curtain should be deployed to protect child occupants. The objective of this study is to
use a scalable MAthematical DYnamic MOdels (MADYMO) model of a child occupant to estimate the
distributions of possible head impact locations as a function of crash type, vehicle interior
characteristics, and child size. To achieve this goal, a series of simulations using a scalable MADYMO
child-ATD model was conducted. The geometries of the second-row compartment from 5 vehicles
were recorded using a laser scanner to provide high-resolution data for assessing probable head
contact zones. Distributions of lateral and longitudinal delta V were calculated as a function of PDOF
using the NASS-CDS dataset to provide proper simulation conditions based on real-world crashes.
Simulations of crashes ranging from pure frontal to pure side impact (9 o’clock to 3 o’clock) with child
ATDs with and without backless boosters were conducted using UMTRI’s parametric child ATD model
in MADYMO, UMTRI's child ATD positioning procedure, and UMTRI's automated belt-fit and crash
simulation system. The simulation results were used to create a model of the spatial distribution of
head trajectories based on child body size and crash direction. By combining the head motion model
and the vehicle second-row geometry models, the likely head contact zones with respect to interior
components were identified. The findings of this study provide a reference for future vehicle rear
compartment design to reduce head injuries for older children.National Highway Traffic Safety Administrationhttps://deepblue.lib.umich.edu/bitstream/2027.42/154006/1/UMTRI-2012-20.pd
Long-Term Stability of Horseshoe Orbits
Unlike Trojans, horseshoe coorbitals are not generally considered to be
long-term stable (Dermott and Murray, 1981; Murray and Dermott, 1999). As the
lifetime of Earth's and Venus's horseshoe coorbitals is expected to be about a
Gyr, we investigated the possible contribution of late-escaping inner planet
coorbitals to the lunar Late Heavy Bombardment. Contrary to analytical
estimates, we do not find many horseshoe objects escaping after first 100 Myr.
In order to understand this behaviour, we ran a second set of simulations
featuring idealized planets on circular orbits with a range of masses. We find
that horseshoe coorbitals are generally long lived (and potentially stable) for
systems with primary-to-secondary mass ratios larger than about 1200. This is
consistent with results of Laughlin and Chambers (2002) for equal-mass pairs or
coorbital planets and the instability of Jupiter's horseshoe companions (Stacey
and Connors, 2008). Horseshoe orbits at smaller mass ratios are unstable
because they must approach within 5 Hill radii of the secondary. In contrast,
tadpole orbits are more robust and can remain stable even when approaching
within 4 Hill radii of the secondary.Comment: Accepted for MNRA
Determining the probability of cyanobacterial blooms: the application of Bayesian networks in multiple lake systems
A Bayesian network model was developed to assess the combined influence of nutrient conditions and climate on the occurrence of cyanobacterial blooms within lakes of diverse hydrology and nutrient supply. Physicochemical, biological, and meteorological observations were collated from 20 lakes located at different latitudes and characterized by a range of sizes and trophic states. Using these data, we built a Bayesian network to (1) analyze the sensitivity of cyanobacterial bloom development to different environmental factors and (2) determine the probability that cyanobacterial blooms would occur. Blooms were classified in three categories of hazard (low, moderate, and high) based on cell abundances. The most important factors determining cyanobacterial bloom occurrence were water temperature, nutrient availability, and the ratio of mixing depth to euphotic depth. The probability of cyanobacterial blooms was evaluated under different combinations of total phosphorus and water temperature. The Bayesian network was then applied to quantify the probability of blooms under a future climate warming scenario. The probability of the "high hazardous" category of cyanobacterial blooms increased 5% in response to either an increase in water temperature of 0.8°C (initial water temperature above 24°C) or an increase in total phosphorus from 0.01 mg/L to 0.02 mg/L. Mesotrophic lakes were particularly vulnerable to warming. Reducing nutrient concentrations counteracts the increased cyanobacterial risk associated with higher temperatures
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