17 research outputs found
THE RELATIONSHIP OF TEST AND GENERAL ANXIETY, DIFFICULTY OF TASK, AND EXPERIMENTAL INSTRUCTIONS TO TEST PERFORMANCE
Abstract not availabl
Recommendations for speed management strategies and policies
Aanbevelingen worden gedaan voor harmonisatie van snelheden op 4 typen wegen in Europa en voor middelen om verkeersveilige snelheden te bewerkstelligen (waaronder intelligente snelheidsadaptatie in de auto)
The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea
The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range
on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene
eruptions worldwide. The resulting ash is found as a visible sediment layer
in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland.
This large geographic distribution, combined with the fact that the eruption
is relatively well constrained in time using radiocarbon dating of lake
sediments and annual layer counts in ice cores, makes it an excellent
stratigraphic marker for dating and correlating mid–late Holocene sediment
and paleoclimate records. This study presents the outcome of a targeted
search for the Aniakchak tephra in a marine sediment core from the Arctic
Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in
Herald Canyon, western Chukchi Sea. High concentrations of tephra shards,
with a geochemical signature matching that of Aniakchak ash, were observed
across a more than 1.5 m long sediment sequence. Since the primary input of
volcanic ash is through atmospheric transport, and assuming that bioturbation
can account for mixing up to ca. 10 cm of the marine sediment deposited at
the coring site, the broad signal is interpreted as sustained reworking at
the sediment source input. The isochron is therefore placed at the base of
the sudden increase in tephra concentrations rather than at the maximum
concentration. This interpretation of major reworking is strengthened by
analysis of grain size distribution which points to ice rafting as an
important secondary transport mechanism of volcanic ash. Combined with
radiocarbon dates on mollusks in the same sediment core, the volcanic marker
is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major
influence of typically carbon-old Pacific waters, and it agrees well with
recent estimates of ΔR along the northwest Alaskan coast, possibly
indicating stable oceanographic conditions during the second half of the
Holocene. Our use of a volcanic absolute age marker to obtain the marine
reservoir age offset is the first of its kind in the Arctic Ocean and
provides an important framework for improving chronologies and correlating
marine sediment archives in this region. Core 2PC has a high sediment
accumulation rate averaging 200 cm kyr−1 throughout the last
4000Â years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in
the Chukchi Sea
Effects on Driver’s Behavior of Illegal Pedestrian Crossings
The aim of this study was to analyze the driver behavior during the interaction with a pedestrian crossing into and outside the zebra crossing. 42 participants experienced different conditions of driver-pedestrian interactions (no pedestrian, legal and illegal crossings). The drivers’ behavior variables were collected from the drivers’ speed profiles, which were plotted in the last 150Â m in advance of the collision point. Based on the vehicle dynamics, more critical driver’s speed behaviors were revealed for illegal pedestrian crossings, for which the driver adopted abrupt yielding maneuver compared to the legal crossing condition. Moreover, higher accident rates were recorded when drivers interacted with jaywalkers. The results confirm that adequate pedestrian paths should be planned in order to avoid jaywalker conditions and pedestrian detection systems could significantly help the driver in the condition of illegal pedestrian crossing behavior