33 research outputs found
Output Impedance Improvement Using Coupled Inductors
When using a single DC/DC converter with multiple outputs and having a buck topology, which has one filter inductor per output, the designer can choose to couple these outputs together. This paper demonstrates additional benefits of coupling output inductors together. Apart from saving mass and volume, and due to an improved small signal behaviour it also reduces the output impedance of the regulated output. The paper will analyse a seven output push-pull converter used as a space power converter module and verify the theoretical results with experimental measurements
Students' perception on learning methods in engineering disciplines
This article is (c) Emerald Group Publishing and permission has been granted for this version to appear here (please insert the web address here). Emerald does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Emerald Group Publishing Limited.[EN] Purpose - This study explores the preferences for learning methods among the students of seven engineering disciplines in a Spanish technical university. The purpose of this paper is to investigate the students' views and from them contribute to the knowledge of the effectiveness of learning methodologies.
Design/methodology/approach - An online anonymous questionnaire survey was adopted to collect students' perceptions. Seven learning methods were compared in seven engineering degrees. The authors sampled 1660 students, and 426 completed responses were analysed. In addition to a descriptive analysis of the results, a multiple correspondence analysis (MCA) was performed using R data processing software.
Findings - It was found that project-based learning and problem-based learning were perceived as the more effective ones. MCA identified response patterns between the preference and the efficiency of learning methods showing that students can be classified into two groups according to their preferred level of activeness in learning.
Research limitations/implications - The study focusses on a single technical university and not all engineering degrees could be sampled. However, five different engineering fields were studied and no significant differences among them were found.
Practical implications - The results add up to the known literature showing that students have different learning needs and consequently they perceive some methods as more effective. Instructors can use this information to strengthen their learning activities. Results also suggest that students can be classified into two groups in relation to their level of activeness in learning. This can also help to enhance general student motivation if two paths with different levels of activeness are planned.
Originality/value - No previous studies have compared several learning methods in different engineering fields. Thus, this study contributes to fill this gap and contributes to the body of evidence around learning methodologies from the perspective of students.Vidal Rodriguez, B.; Fenollosa Ribera, ML.; Ribal, J.; Sanchis Kilders, P.; García-Rupérez, J.; Bes-Piá, M.; Blasco-Tamarit, E.... (2022). Students' perception on learning methods in engineering disciplines. Journal of Applied Research in Higher Education. 14(3):946-957. https://doi.org/10.1108/JARHE-01-2021-0041S94695714
Magnetic fields inferred by Solar Orbiter: A comparison between SO/PHI-HRT and SDO/HMI
The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic
Imager on board the Solar Orbiter spacecraft (SO/PHI) and the Helioseismic and
Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both infer
the photospheric magnetic field from polarised light images. SO/PHI is the
first magnetograph to move out of the Sun--Earth line and will provide
unprecedented access to the Sun's poles. This provides excellent opportunities
for new research wherein the magnetic field maps from both instruments are used
simultaneously. We aim to compare the magnetic field maps from these two
instruments and discuss any possible differences between them. We used data
from both instruments obtained during Solar Orbiter's inferior conjunction on 7
March 2022. The HRT data were additionally treated for geometric distortion and
degraded to the same resolution as HMI. The HMI data were re-projected to
correct for the separation between the two observatories.
SO/PHI-HRT and HMI produce remarkably similar line-of-sight magnetograms, with
a slope coefficient of , an offset below G, and a Pearson correlation
coefficient of . However, SO/PHI-HRT infers weaker line-of-sight fields
for the strongest fields. As for the vector magnetic field, SO/PHI-HRT was
compared to both the -second and -second HMI vector magnetic field:
SO/PHI-HRT has a closer alignment with the -second HMI vector. In the weak
signal regime ( G), SO/PHI-HRT measures stronger and more horizontal
fields than HMI, very likely due to the greater noise in the SO/PHI-HRT data.
In the strong field regime ( G), HRT infers lower field strengths
but with similar inclinations (a slope of ) and azimuths (a slope of
). The slope values are from the comparison with the HMI -second
vector.Comment: 10 pages, 5 figures, accepted for publication in A&A; manuscript is a
part of Astronomy & Astrophysics special issue: Solar Orbiter First Results
(Nominal Mission Phase
Wavefront error of PHI/HRT on Solar Orbiter at various heliocentric distances
We use wavefront sensing to characterise the image quality of the the High
Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI)
data products during the second remote sensing window of the Solar Orbiter (SO)
nominal mission phase. Our ultimate aims are to reconstruct the HRT data by
deconvolving with the HRT point spread function (PSF) and to correct for the
effects of optical aberrations on the data. We use a pair of focused--defocused
images to compute the wavefront error and derive the PSF of HRT by means of a
phase diversity (PD) analysis. The wavefront error of HRT depends on the
orbital distance of SO to the Sun. At distances \,au, the wavefront error
is small, and stems dominantly from the inherent optical properties of HRT. At
distances \,au, the thermo-optical effect of the Heat Rejection Entrance
Window (HREW) becomes noticeable. We develop an interpolation scheme for the
wavefront error that depends on the thermal variation of the HREW with the
distance of SO to the Sun. We also introduce a new level of image
reconstruction, termed `aberration correction', which is designed to reduce the
noise caused by image deconvolution while removing the aberrations caused by
the HREW. The computed PSF via phase diversity significantly reduces the
degradation caused by the HREW in the near-perihelion HRT data. In addition,
the aberration correction increases the noise by a factor of only
compared to the factor of increase that results from the usual PD
reconstructions
Stereoscopic disambiguation of vector magnetograms: first applications to SO/PHI-HRT data
Spectropolarimetric reconstructions of the photospheric vector magnetic field
are intrinsically limited by the 180-ambiguity in the orientation of
the transverse component. So far, the removal of such an ambiguity has required
assumptions about the properties of the photospheric field, which makes
disambiguation methods model-dependent. The basic idea is that the unambiguous
line-of-sight component of the field measured from one vantage point will
generally have a non-zero projection on the ambiguous transverse component
measured by the second telescope, thereby determining the ``true'' orientation
of the transverse field. Such an idea was developed and implemented in the
Stereoscopic Disambiguation Method (SDM), which was recently tested using
numerical simulations. In this work we present a first application of the SDM
to data obtained by the High Resolution Telescope (HRT) onboard Solar Orbiter
during the March 2022 campaign, when the angle with Earth was 27 degrees. The
method is successfully applied to remove the ambiguity in the transverse
component of the vector magnetogram solely using observations (from HRT and
from the Helioseismic and Magnetic Imager), for the first time. The SDM is
proven to provide observation-only disambiguated vector magnetograms that are
spatially homogeneous and consistent. A discussion about the sources of error
that may limit the accuracy of the method, and of the strategies to remove them
in future applications, is also presented.Comment: 32 pages, 12 figures, accepted in A&A on 09/07/202
Intensity contrast of solar network and faculae close to the solar limb, observed from two vantage points
The brightness of faculae and network depends on the angle at which they are
observed and the magnetic flux density. Close to the limb, assessment of this
relationship has until now been hindered by the increasingly lower signal in
magnetograms. This preliminary study aims at highlighting the potential of
using simultaneous observations from different vantage points to better
determine the properties of faculae close to the limb. We use data from the
Solar Orbiter/Polarimetric and Helioseismic Imager (SO/PHI), and the Solar
Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI), recorded at
angular separation of their lines of sight at the Sun. We use
continuum intensity observed close to the limb by SO/PHI and complement it with
the co-observed from SDO/HMI, originating closer to disc centre
(as seen by SDO/HMI), thus avoiding the degradation of the magnetic field
signal near the limb. We derived the dependence of facular brightness in the
continuum on disc position and magnetic flux density from the combined
observations of SO/PHI and SDO/HMI. Compared with a single point of view, we
were able to obtain contrast values reaching closer to the limb and to lower
field strengths. We find the general dependence of the limb distance at which
the contrast is maximum on the flux density to be at large in line with single
viewpoint observations, in that the higher the flux density is, the closer the
turning point lies to the limb. There is a tendency, however, for the maximum
to be reached closer to the limb when determined from two vantage points. We
note that due to the preliminary nature of this study, these results must be
taken with caution. Our analysis shows that studies involving two viewpoints
can significantly improve the detection of faculae near the solar limb and the
determination of their brightness contrast relative to the quiet Sun
The ratio of horizontal to vertical displacement in solar oscillations estimated from combined SO/PHI and SDO/HMI observations
In order to make accurate inferences about the solar interior using
helioseismology, it is essential to understand all the relevant physical
effects on the observations. One effect to understand is the (complex-valued)
ratio of the horizontal to vertical displacement of the p- and f-modes at the
height at which they are observed. Unfortunately, it is impossible to measure
this ratio directly from a single vantage point, and it has been difficult to
disentangle observationally from other effects. In this paper we attempt to
measure the ratio directly using 7.5 hours of simultaneous observations from
the Polarimetric and Helioseismic Imager on board Solar Orbiter and the
Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. While
image geometry problems make it difficult to determine the exact ratio, it
appears to agree well with that expected from adiabatic oscillations in a
standard solar model. On the other hand it does not agree with a commonly used
approximation, indicating that this approximation should not be used in
helioseismic analyses. In addition, the ratio appears to be real-valued.Comment: Accepted for publication in Astronomy & Astrophysics. 8 pages, 8
figure
Coronal voids and their magnetic nature
Context:
Extreme ultraviolet (EUV) observations of the quiet solar atmosphere reveal extended regions of weak emission compared to the ambient quiescent corona. The magnetic nature of these coronal features is not well understood.
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Aims:
We study the magnetic properties of the weakly emitting extended regions, which we name coronal voids. In particular, we aim to understand whether these voids result from a reduced heat input into the corona or if they are associated with mainly unipolar and possibly open magnetic fields, similar to coronal holes.
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Methods:
We defined the coronal voids via an intensity threshold of 75% of the mean quiet-Sun (QS) EUV intensity observed by the high-resolution EUV channel (HRIEUV) of the Extreme Ultraviolet Imager on Solar Orbiter. The line-of-sight magnetograms of the same solar region recorded by the High Resolution Telescope of the Polarimetric and Helioseismic Imager allowed us to compare the photospheric magnetic field beneath the coronal voids with that in other parts of the QS.
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Results:
The coronal voids studied here range in size from a few granules to a few supergranules and on average exhibit a reduced intensity of 67% of the mean value of the entire field of view. The magnetic flux density in the photosphere below the voids is 76% (or more) lower than in the surrounding QS. Specifically, the coronal voids show much weaker or no network structures. The detected flux imbalances fall in the range of imbalances found in QS areas of the same size.
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Conclusions:
We conclude that coronal voids form because of locally reduced heating of the corona due to reduced magnetic flux density in the photosphere. This makes them a distinct class of (dark) structure, different from coronal holes
CMAG: a mission to study and monitor the inner corona magnetic field
Measuring magnetic fields in the inner corona, the interface between the solar chromosphere and outer corona, is of paramount importance if we aim to understand the energetic transformations taking place there, and because it is at the origin of processes that lead to coronal heating, solar wind acceleration, and of most of the phenomena relevant to space weather. However, these measurements are more difficult than mere imaging because polarimetry requires differential photometry. The coronal magnetograph mission (CMAG) has been designed to map the vector magnetic field, line-of-sight velocities, and plane-of-the-sky velocities of the inner corona with unprecedented spatial and temporal resolutions from space. This will be achieved through full vector spectropolarimetric observations using a coronal magnetograph as the sole instrument on board a spacecraft, combined with an external occulter installed on another spacecraft. The two spacecraft will maintain a formation flight distance of 430 m for coronagraphic observations, which requires a 2.5 m occulter disk radius. The mission will be preferentially located at the Lagrangian L5 point, offering a significant advantage for solar physics and space weather research. Existing ground-based instruments face limitations such as atmospheric turbulence, solar scattered light, and long integration times when performing coronal magnetic field measurements. CMAG overcomes these limitations by performing spectropolarimetric measurements from space with an external occulter and high-image stability maintained over time. It achieves the necessary sensitivity and offers a spatial resolution of 2.5″ and a temporal resolution of approximately one minute, in its nominal mode, covering the range from 1.02 solar radii to 2.5 radii. CMAG relies on proven European technologies and can be adapted to enhance any other solar mission, offering potential significant advancements in coronal physics and space weather modeling and monitoring