2,816 research outputs found
Deepwater Drilling: Law, Policy, and Economics of Firm Organization and Safety
Although the causes of the Deepwater Horizon spill are not yet conclusively identified, significant attention has focused on the safety-related policies and practicesâoften referred to as the safety cultureâof BP and other firms involved in drilling the well. This paper defines and characterizes the economic and policy forces that affect safety culture and identifies reasons why those forces may or may not be adequate or effective from the publicâs perspective. Two potential justifications for policy intervention are that: a) not all of the social costs of a spill may be internalized by a firm; and b) there may be principal-agency problems within the firm, which could be reduced by external monitoring. The paper discusses five policies that could increase safety culture and monitoring: liability, financial responsibility (a requirement that a firmâs assets exceed a threshold), government oversight, mandatory private insurance, and risk-based drilling fees. We find that although each policy has a positive effect on safety culture, there are important differences and interactions that must be considered. In particular, the latter three provide external monitoring. Furthermore, raising liability caps without mandating insurance or raising financial responsibility requirements could have a small effect on the safety culture of small firms that would declare bankruptcy in the event of a large spill. The paper concludes with policy recommendations for promoting stronger safety culture in offshore drilling; our preferred approach would be to set a liability cap for each well equal to the worst-case social costs of a spill, and to require insurance up to the cap.Deepwater Horizon, BP oil spill, safety culture, government policy, liability caps, financial responsibility, insurance
Progress towards recalibration of spectrographs
The spectral resolution of a spectrograph depends on the input slit width, the diffraction grating grooves and the number of imaging sensor/detector pixels. Due to the proprietary nature of spectrograph designs, recalibration by end-users can be challenging. Most calibration procedures currently published are applicable to in-house instruments or spectrographs with access to the internal specifications. Narrowing the input slit improves the resolution but also reduces the throughput of the imaging system. We attempted to recalibrate an Offner-based spectrograph by using a larger detector plane (an imaging system with a larger sensor), to vary the distance along the focal plane; and by utilising lens optics. Basic experiments were conducted by varying the distance from the exit window and inserting a lens to magnify the spectrograph output onto the larger detector plane. We concluded that the calibration could not be achieved using simple optics within the scope of our experiments. This article addresses a gap in literature that does not present the research community with the unsuccessful steps that are not applicable to similar problem statements. The alternative would be to rely on reflective optics, but this approach may reduce portability
Thermal stereo odometry for UAVs
In the last decade, visual odometry (VO) has attracted significant research attention within the computer vision community. Most of the works have been carried out using standard visible-band cameras. These sensors offer numerous advantages but also suffer from some drawbacks such as illumination variations and limited operational time (i.e., daytime only). In this paper, we explore techniques that allow us to extend the concepts beyond the visible spectrum. We introduce a localization solution based on a pair of thermal cameras. We focus on VO and demonstrate the accuracy of the proposed solution in daytime as well as night-time. The first challenge with thermal cameras is their geometric calibration. Here, we propose a solution to overcome this issue and enable stereopsis. VO requires a good set of feature correspondences. We use a combination of Fast-Hessian detector with for Fast Retina Keypoint descriptor for that purpose. A range of optimization techniques can be used to compute the incremental motion. Here, we propose the double dogleg algorithm and show that it presents an interesting alternative to the commonly used Levenberg-Marquadt approach. In addition, we explore thermal 3-D reconstruction and show that similar performance to the visible-band can be achieved. In order to validate the proposed solution, we build an innovative experimental setup to capture various data sets, where different weather and time conditions are considered
Galactic winds and stellar populations in Lyman emitting galaxies at z ~ 3.1
We present a sample of 33 spectroscopically confirmed z ~ 3.1
Ly-emitting galaxies (LAEs) in the Cosmological Evolution Survey
(COSMOS) field. This paper details the narrow-band survey we conducted to
detect the LAE sample, the optical spectroscopy we performed to confirm the
nature of these LAEs, and a new near-infrared spectroscopic detection of the [O
III] 5007 \AA\ line in one of these LAEs. This detection is in addition to two
[O III] detections in two z ~ 3.1 LAEs we have reported on previously (McLinden
et al 2011). The bulk of the paper then presents detailed constraints on the
physical characteristics of the entire LAE sample from spectral energy
distribution (SED) fitting. These characteristics include mass, age,
star-formation history, dust content, and metallicity. We also detail an
approach to account for nebular emission lines in the SED fitting process -
wherein our models predict the strength of the [O III] line in an LAE spectrum.
We are able to study the success of this prediction because we can compare the
model predictions to our actual near-infrared observations both in galaxies
that have [O III] detections and those that yielded non-detections. We find a
median stellar mass of 6.9 10 M and a median star
formation rate weighted stellar population age of 4.5 10 yr. In
addition to SED fitting, we quantify the velocity offset between the [O III]
and Ly lines in the galaxy with the new [O III] detection, finding that
the Ly line is shifted 52 km s redwards of the [O III] line,
which defines the systemic velocity of the galaxy.Comment: 38 pages, 27 figures, 4 tables, Accepted for publication in MNRA
Who Are Our Fans: An Application of Principal Component-Cluster Technique Analysis to Market Segmentation of College Football Fans
A 66-question online marketing survey of 2,800 football fans who had purchased tickets to a Division I, Power 5 (P5) university football game was conducted in order to understand the fan base and provide better services and targeted marketing. Principal Component Analysis was employed to combine responses from multiple questions about purchase behavior, on-site satisfaction, demographics, and other criteria. Subsequent market segmentation via cluster analysis indicated that 95% of the survey respondents could be categorized into one of five clusters. The identified fan perceptions and evaluations resulted in the P5 athletic department taking specific actions to improve targeted marketing activities and enhance game-day experiences, including improving the quality and diversity of food offerings, ensuring smoother ingress and egress, offering more precise ticket packages, and targeting groups through relevant marketing channels. The current research notes the importance of utilizing precision marketing efforts to target specific clusters and then providing appropriate tangible and intangible products and services to maximize initial sales, improve fan experience, and increase the likelihood of repeat purchases
The Dynamical Masses, Densities, and Star Formation Scaling Relations of Lyman Alpha Galaxies
We present the first dynamical mass measurements for Lyman alpha galaxies at
high redshift, based on velocity dispersion measurements from rest-frame
optical emission lines and size measurements from HST imaging, for a sample of
nine galaxies drawn from four surveys. These measurements enable us to study
the nature of Lyman alpha galaxies in the context of galaxy scaling relations.
The resulting dynamical masses range from 1e9 to 1e10 solar masses. We also fit
stellar population models to our sample, and use them to plot the Lyman alpha
sample on a stellar mass vs. line width relation. Overall, the Lyman alpha
galaxies follow well the scaling relation established by observing star forming
galaxies at lower redshift (and without regard for Lyman alpha emission),
though in 1/3 of the Lyman alpha galaxies, lower-mass fits are also acceptable.
In all cases, the dynamical masses agree with established stellarmass-linewidth
relation. Using the dynamical masses as an upper limit on gas mass, we show
that Lyman alpha galaxies resemble starbursts (rather than "normal" galaxies)
in the relation between gas mass surface density and star formation activity,
in spite of relatively modest star formation rates. Finally, we examine the
mass densities of these galaxies, and show that their future evolution likely
requires dissipational ("wet") merging. In short, we find that Lyman alpha
galaxies are low mass cousins of larger starbursts.Comment: Submitted to The Astrophysical Journal. 23 pp including three figures
and four table
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