79 research outputs found
The Development of Ethical Reasoning: A Comparison of Online versus Hybrid Delivery Modes of Ethics Instruction
There is a concerted effort to improve online learning opportunities in higher education, including in the domain of engineering ethics. The benefits of online learning include ease in sharing course content, flexibility in the timing of participation, and increased variation in delivery modes for course material. However, the effect of online and hybrid participation on developing ethical reasoning in students is largely unknown, and interactive cases and dialogic learning are central to the pedagogy in ethics courses. An opportunity to fill this knowledge gap occurred while testing a new pedagogy for enhancing ethical reasoning among engineering graduate students, implemented in a graduate-level course over three offerings in Spring 2014, Summer 2014, and Spring 2015. Of the 29 students enrolled, 11 participated on-campus in a weekly class discussion-based lecture, and 18 completed the majority of course activities online. This multi-phase study presents results from a comparative analysis of the differences in ethical reasoning development and perception of course activities across these groups. Both groups of students showed substantial gains in their ethical reasoning development. Furthermore, changes in ethical reasoning were not significantly different when students participated in the on-line only versus an on-line/in-class or “hybrid” format. Nonetheless, analysis from post-course surveys indicated that the hybrid group perceived course activities more favorably than did their on-line only peers. In sum, these results indicate that on-line ethics interventions can be designed to be as impactful in developing ethical reasoning as formats that include an in-class component, although students may be more satisfied with ethics education when they have the opportunity for face-to-face, in-class interaction with peers and instructors
Spectral and temporal properties of the ultra-luminous X-ray pulsar in M82 from 15 years of Chandra observations and analysis of the pulsed emission using NuSTAR
The recent discovery by Bachetti et al. (2014) of a pulsar in M82 that can
reach luminosities of up to 10^40 ergs s^-1, a factor of ~100 the Eddington
luminosity for a 1.4 Msol compact object, poses a challenge for accretion
physics. In order to better understand the nature of this source and its duty
cycle, and in the light of several physical models that have been subsequently
published, we conduct a spectral and temporal analysis of the 0.5-8 keV X-ray
emission from this source from 15 years of Chandra observations. We fit the
Chandra spectra of the pulsar with a power-law model and a disk black body
model, subjected to interstellar absorption in M82. We carefully assess for the
effect of pile-up in our observations, where 4/19 observations have a pile-up
fraction >10%, which we account for during spectral modeling with a convolution
model. When fitted with a power-law model, the average photon index when the
source is at high luminosity (L_X>10^39 ergs s^-1) is Gamma=1.33+/-0.15. For
the disk black body model, the average temperature is T=3.24+/-0.65 keV,
consistent with other luminous X-ray pulsars. We also investigated the
inclusion of a soft excess component and spectral break, finding that the
spectra are also consistent with these features common to luminous X-ray
pulsars. In addition, we present spectral analysis from NuSTAR over the 3-50
keV range where we have isolated the pulsed component. We find that the pulsed
emission in this band is best fit by a power-law with a high-energy cut-off,
where Gamma=0.6+/-0.3 and E_C=14^{+5}_{-3} keV. While the pulsar has previously
been identified as a transient, we find from our longer-baseline study that it
has been remarkably active over the 15-year period, where for 9/19 (47%)
observations that we analyzed, the pulsar appears to be emitting at a
luminosity in excess of 10^39 ergs s^-1, greater than 10 times its Eddington
limit.Comment: Accepted for publication by Ap
On the magnetic field in M51 ULX-8
The reported discovery of a cyclotron resonance scattering feature (CRSF) in
the spectrum of M51 ULX-8 may provide an important clue as to the nature of the
magnetic field in those ultraluminous X-ray sources hosting neutron stars. In
this paper we present the covariance (linearly correlated variability) spectrum
of M51 ULX-8 on long (> 2000s) timescales. This allows us to unambiguously
decompose the spectrum which requires multiple components in order to explain
the broad-band emission. Having a clearer picture of the spectral decomposition
leads to various tests for the dipole field strength of the neutron star which
can be extended to other ULXs when certain criteria are met. In the case of M51
ULX-8, we rule out a very strong (~10^15 G) dipole solution with either a sub-
or super-critical disc. Instead, our tests indicate an upper limit on the
dipole field of ~10^12 G, and a classical super-critical inflow, similar to
that inferred in other ULXs found to harbour neutron stars, although we do not
rule out the presence of an additional, strong (~10^15 G) multipole field
falling off steeply with distance from the neutron star.Comment: 9 pages, 4 figures, accepted to MNRAS, updated following correction
A ~60-day super-orbital period originating from the ultraluminous X-ray pulsar in M82
Ultraluminous X-ray (ULX) pulsars are a new class of object powered by
apparent super-critical accretion onto magnetized neutron stars. Three sources
in this class identified so far; M82 X-2, NGC 5907 ULX-1 and NGC 7793 P13, have
been found to have two properties in common; -s spin periods, and for
NGC 5907 ULX-1 and NGC 7793 P13 periodic X-ray flux modulations on timescales
of days. M82 X-2 resides in a crowded field that includes the ULX
M82 X-1 separated from X-2 by 5", as well as other bright point sources. A
60-day modulation has been observed from the region but the origin has been
difficult to identify; both M82 X-1 and X-2 have been suggested as the source.
In this paper we present the analysis of a systematic monitoring campaign by
Chandra, the only X-ray telescope capable of resolving the crowded field. From
a simple Lomb-Scargle periodogram analysis and a more sophisticated Gaussian
Process analysis we find that only X-2 exhibits a periodic signal around 60
days supporting previous claims that it is the origin. We also construct a
phase-averaged flux profile of the modulations from higher cadence Swift/XRT
data and find that the flux variations in the Chandra data are fully consistent
with the flux profile. Since the orbit of the neutron star and its companion is
known to be 2.5 days, the -day period must be super-orbital in origin.
The flux of the modulations varies by a factor of 100 from minimum to
maximum, with no evidence for spectral variations, making the origin difficult
to explain.Comment: Accepted for publication in the Astrophysical Journa
Applying Phenomenography to Develop a Comprehensive Understanding of Ethics in Engineering Practice
This Work-in-Progress Research paper describes (1) the contemporary research space on ethics education in engineering; (2) our long-term research plan; (3) the theoretical underpinnings of Phase 1 of our research plan (phenomenography); and (4) the design and developmental process of a phenomenographic interview protocol to explore engineers' experiences with ethics. Ethical behavior is a complex phenomenon that is complicated by the institutional and cultural contexts in which it occurs. Engineers also have varied roles and often work in a myriad of capacities that influence their experiences with and understanding of ethics in practice. We are using phenomenography, a qualitative research approach, to explore and categorize the ways engineers experience and understand ethical engineering practice. Specifically, phenomenography will allow us to systematically investigate the range and complexity of ways that engineers experience ethics in professional practice in the health products industry. Phenomenographic data will be obtained through a specialized type of semi-structured interview. Here we introduce the design of our interview protocol and its four sections: Background, Experience, Conceptual, and Summative. We also describe our iterative process for framing questions throughout each section
MaRCoS, an open-source electronic control system for low-field MRI
Every magnetic resonance imaging (MRI) device requires an electronic control
system that handles pulse sequences and signal detection and processing. Here
we provide details on the architecture and performance of MaRCoS, a MAgnetic
Resonance COntrol System developed by an open international community of
low-field MRI researchers. MaRCoS is inexpensive and can handle cycle-accurate
sequences without hard length limitations, rapid bursts of events, and
arbitrary waveforms. It can also be easily adapted to meet further
specifications required by the various academic and private institutions
participating in its development. We describe the MaRCoS hardware, firmware and
software that enable all of the above, including a Python-based graphical user
interface for pulse sequence implementation, data processing and image
reconstruction.Comment: 10 pages, 4 figure
The role of tungsten oxide in enhancing the carbon monoxide tolerance of platinum-based hydrogen oxidation catalysts
Significant reductions in total cost of ownership can be realized by engineering PEM fuel cells to run on low-purity hydrogen. One of the main drawbacks of low-purity hydrogen fuels is the carbon monoxide fraction, which poisons platinum electrocatalysts and reduces the power output below useful levels. Platinum-Tungsten oxide catalyst systems have previously shown high levels of CO tolerance during both ex situ and in situ investigations. In this work, we explore the mechanism of enhanced tolerance using in situ electrochemical attenuated total reflection-infrared (ATR-IR) and Raman spectroscopy methods and investigate, using a mixture of Pt/C and WO3 powders, the role of the WV/WVI redox couple in the oxidation of adsorbed CO
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