6,185 research outputs found
Group and individual decision-making in project risk management
This research has shown how the nature of the construction project has become
increasingly complex and has highlighted how project management decision-making
has been supplemented with the use of risk management strategies. Subsequently the
use of risk management strategies in construction project execution has had some of its
weaknesses exposed, namely the failure of such strategies to consider the role of the
individual within the risk management process. Consequently this research has
undertaken an investigation to ascertain and understand the nature and impact of
individual decision-makers upon the decision-making process. The attributes of and
influences upon individual decision-making, risk and uncertainty perceptions and
preferences have been explored and discussed in some detail. From those the `risk
prism', a metaphor for the perception and preference of risk and uncertainty, was
developed to explore the manner in which these decision-making attributes function.
An investigation was undertaken to replicate the `risky shift' phenomenon in decisionmaking
groups populated by construction project management professionals. The
results of this investigation ascertained the influence of the group environment upon
construction management decision makers, namely that individuals were influenced to
accept greater uncertainty in a group decision environment. Subsequently a case study
investigation of an organisations attempt to introduce a new risk management strategy
was undertaken from which an enhanced understanding of the group discussion and
decision-making environment was ascertained.
As a result of these investigations an improved risk management process was
developed and is presented within this dissertation
SALT Long-slit Spectroscopy of Luminous Obscured Quasars: An Upper Limit on the Size of the Narrow-Line Region?
We present spatially resolved long-slit spectroscopy from the Southern
African Large Telescope (SALT) to examine the spatial extent of the narrow-line
regions (NLRs) of a sample of 8 luminous obscured quasars at 0.10 < z < 0.43.
Our results are consistent with an observed shallow slope in the relationship
between NLR size and L_[OIII], which has been interpreted to indicate that NLR
size is limited by the density and ionization state of the NLR gas rather than
the availability of ionizing photons. We also explore how the NLR size scales
with a more direct measure of instantaneous AGN power using mid-IR photometry
from WISE, which probes warm to hot dust near the central black hole and so,
unlike [OIII], does not depend on the properties of the NLR. Using our results
as well as samples from the literature, we obtain a power-law relationship
between NLR size and L_8micron that is significantly steeper than that observed
for NLR size and L_[OIII]. We find that the size of the NLR goes approximately
as L^(1/2)_8micron, as expected from the simple scenario of constant-density
clouds illuminated by a central ionizing source. We further see tentative
evidence for a flattening of the relationship between NLR size and L_8micron at
the high luminosity end, and propose that we are seeing a limiting NLR size of
10 - 20 kpc, beyond which the availability of gas to ionize becomes too low. We
find that L_[OIII] ~ L_8micron^(1.4), consistent with a picture in which the
L_[OIII] is dependent on the volume of the NLR. These results indicate that
high-luminosity quasars have a strong effect in ionizing the available gas in a
galaxy.Comment: 9 Pages, 5 figures, accepted to Ap
Composite Spectral Energy Distributions and Infrared-Optical Colors of Type 1 and Type 2 Quasars
We present observed mid-infrared and optical colors and composite spectral
energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars
selected from Sloan Digital Sky Survey (SDSS) spectroscopy. A significant
fraction of powerful quasars are obscured by dust, and are difficult to detect
in optical photometric or spectroscopic surveys. However these may be more
easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using
samples of SDSS type 1 type 2 matched in redshift and [OIII] luminosity, we
produce composite rest-frame 0.2-15 micron SEDs based on SDSS, UKIDSS, and
Wide-Field Infrared Survey Explorer (WISE) photometry and perform model fits
using simple galaxy and quasar SED templates. The SEDs of type 1 and 2 quasars
are remarkably similar, with the differences explained primarily by the
extinction of the quasar component in the type 2 systems. For both types of
quasar, the flux of the AGN relative to the host galaxy increases with AGN
luminosity (L_[OIII]) and redder observed MIR color, but we find only weak
dependencies of the composite SEDs on mechanical jet power as determined
through radio luminosity. We conclude that luminous quasars can be effectively
selected using simple MIR color criteria similar to those identified previously
(W1-W2 > 0.7 [Vega]), although these criteria miss many heavily obscured
objects. Obscured quasars can be further identified based on optical-IR colors
(for example, (u-W3 [AB]) > 1.4(W1-W2 [Vega])+3.2). These results illustrate
the power of large statistical studies of obscured quasars selected on the
basis of mid-IR and optical photometry.Comment: Accepted for publication in ApJ; 14 pages, 9 figures, 2 tables;
composite Type 1 and Type 2 quasar SEDs available at
http://www.dartmouth.edu/~hickox/Hickox2017_QSO_SED_Table1.tx
Satellite Telemetry Provides Insight into Where Western Montana Osprey Spend the Winter
During a long-term study of Osprey (Pandion haliaetus) in western Montana on demography and ecotoxicology, migratory information on several birds was collected. It is important to know where these birds migrate and spend the winter because 2/3 of their lives are spent outside Montana. Since virtually nothing was known about where these birds go when they leave the state, in 2012 and 2013 we put satellite transmitters on two families of Osprey (adults and chicks) from nests near Florence, Montana. Telemetry data show that these birds migrate south through a fairly narrow corridor to Arizona and New Mexico, but then go in different directions: some individuals spend the winter in Texas, and others migrate to Mexico and as far south as the Nicaragua-Costa Rica border on both the Atlantic and Pacific coasts. Migration pathways of the adults were very similar for both south-bound and north-bound migrations across multiple years
Electromyographic Activity of Hamstrings and Quadriceps Muscle during Jumping and Landing: Pilot Study
Background and Purpose. The purpose of this pilot study was to see if there was a difference in amount of electromyographic (EMG) activity in the quadriceps (vastus medialis and vastus lateralis) compared to amount of EMG activity in the hamstrings (biceps femoris and semitendinosus) in active male and female subjects during vertical jumping and landing. In addition, we looked at the amount of knee flexion that occurred in the male and female subjects shortly after landing from a vertical jump.
Methods EMG activity was recorded using a Noraxon TeleMyo DTS telemetry unit with a sampling rate of 1 kHz. EMG data was recorded during vertical jumping and landing. EMG activity in two quadriceps muscles (vastus medialis and vastus lateralis) and two hamstring muscles (biceps femoris and semitendinosus) were monitored during the experiment. The subject was also captured on video using the NiNox 125/250 FPS camera system. Subjects consisted of two male and two female athletes in good physical condition with no previous knee pathologies.
Results Differences were found in the quadriceps to hamstring ratio when comparing female to male participants in both single jump (Female 4.42:1, Male 2.38:1) and triple jump landing (Female 5.46:1, Male 1.90:1). Females generally showed higher percent of maximal voluntary contraction in the quadriceps than the males when compared for both jumps. Remarkable differences in knee flexion upon landing were not found between genders in either test.
Conclusion The results of this study showed quadriceps dominance in females as compared to males when landing from a jump. Previous studies have theorized that this level of dominance creates tensile force on the ACL, leading to increased incidence of ACL tears. Strength training focused on hamstring activation with a proper quadriceps to hamstring muscles ratio should be implemented when preventing ACL injuries especially in the female population. Further research is needed to confirm these conclusions and demonstrate clinical relevance
Gemini Long-slit Observations of Luminous Obscured Quasars: Further Evidence for an Upper Limit on the Size of the Narrow-Line Region
We examine the spatial extent of the narrow-line regions (NLRs) of a sample
of 30 luminous obscured quasars at observed with spatially
resolved Gemini-N GMOS long-slit spectroscopy. Using the [OIII]
emission feature, we estimate the size of the NLR using a cosmology-independent
measurement: the radius where the surface brightness falls to 10 erg
s cm arcsec. We then explore the effects of atmospheric
seeing on NLR size measurements and conclude that direct measurements of the
NLR size from observed profiles are too large by 0.1 - 0.2 dex on average, as
compared to measurements made to best-fit S\'{e}rsic or Voigt profiles
convolved with the seeing. These data, which span a full order of magnitude in
IR luminosity () also provide strong evidence that there is a flattening of the
relationship between NLR size and AGN luminosity at a seeing-corrected size of
kpc. The objects in this sample have high luminosities which place
them in a previously under-explored portion of the size-luminosity
relationship. These results support the existence of a maximal size of the
narrow-line region around luminous quasars; beyond this size either there is
not enough gas, or the gas is over-ionized and does not produce enough
[OIII] emission.Comment: 10 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Utilising the risky shift phenomenon in construction project management
The risky shift phenomenon predicts that groups are happier to live with uncertainty
than are the individuals that comprise the group. This paper reports on the replication
of the Wallach et al. (1962) 12 question, choice dilemma questionnaire which
highlights the risky shift and its implications for construction project risk
management
Gemini Long-Slit Observations of Luminous Obscured Quasars: Further Evidence for an Upper Limit on the Size of the Narrow-Line Region
We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 \u3c z \u3c 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10–15 erg s–1 cm–2 arcsec–2. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L 8 μm/erg s–1) = 44.4-45.4), also provide strong evidence that there is a flattening of the relationship between NLR size and active galactic nucleus luminosity at a seeing-corrected size of ~7 kpc. The objects in this sample have high luminosities which place them in a previously under-explored portion of the size-luminosity relationship. These results support the existence of a maximal size of the NLR around luminous quasars; beyond this size, there is either not enough gas or the gas is over-ionized and does not produce enough [O III] λ5007 emission
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