1,550 research outputs found
Deriving 3d point clouds from terrestrial photographs comparison of different sensors and software
Terrestrial photogrammetry nowadays offers a reasonably cheap, intuitive and effective approach to 3D-modelling. However, the
important choice, which sensor and which software to use is not straight forward and needs consideration as the choice will have
effects on the resulting 3D point cloud and its derivatives.
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We compare five different sensors as well as four different state-of-the-art software packages for a single application, the modelling
of a vegetated rock face. The five sensors represent different resolutions, sensor sizes and price segments of the cameras. The
software packages used are: (1) Agisoft PhotoScan Pro (1.16), (2) Pix4D (2.0.89), (3) a combination of Visual SFM (V0.5.22) and
SURE (1.2.0.286), and (4) MicMac (1.0). We took photos of a vegetated rock face from identical positions with all sensors. Then we
compared the results of the different software packages regarding the ease of the workflow, visual appeal, similarity and quality of
the point cloud.
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While PhotoScan and Pix4D offer the user-friendliest workflows, they are also “black-box” programmes giving only little insight
into their processing. Unsatisfying results may only be changed by modifying settings within a module. The combined workflow of
Visual SFM, SURE and CloudCompare is just as simple but requires more user interaction. MicMac turned out to be the most
challenging software as it is less user-friendly. However, MicMac offers the most possibilities to influence the processing workflow.
The resulting point-clouds of PhotoScan and MicMac are the most appealing
Superconducting Vortices and Elliptical Ferromagnetic Textures
In this article an analytical and numerical study of superconducting thin
film with ferromagnetic textures of elliptical geometries in close proximity is
presented. The screening currents induced in the superconductor due to the
magnetic texture are calculated. Close to the superconducting transition
temperature the spontaneous creation of superconducting vortices becomes
energy favorable depending on the value of the magnetization and the
geometrical quantities of the magnetic texture. The creation of vortices by
elliptic dots is more energy favorable than those created by circular ones. The
superconductor covered by elliptic dots array exhibits anisotropic transport
properties.Comment: 4 pages, 5figure
A New Approach to Modelling of a Water Vapour Selective Membrane Module for Improving the Efficiency of Humidity Harvesting
A Two-Field Quintessence Model
We study the dynamics of a quintessence model based on two interacting scalar
fields. The model can account for the (recent) accelerated expansion of the
Universe suggested by astronomical observations. Acceleration can be permanent
or temporary and, for both scenarios, it is possible to obtain suitable values
for the cosmological parameters while satisfying the nucleosynthesis constraint
on the quintessence energy density. We argue that the model dynamics can be
made consistent with a stable zero-energy relaxing supersymmetric vacuum.Comment: 4 pages, 3 eps figures, to be published in Phys. Rev.
Quantum driven Bounce of the future Universe
It is demonstrated that due to back-reaction of quantum effects, expansion of
the universe stops at its maximum and takes a turnaround. Later on, it
contracts to a very small size in finite future time. This phenomenon is
followed by a " bounce" with re-birth of an exponentially expanding
non-singular universe
Pain, Physical and Social Functioning, and Quality of Life in Individuals with Multiple Hereditary Exostoses in the Netherlands
Curvature Inspired Cosmological Scenario
Using modified gravity with non-linear terms of curvature, and (with being the positive real number and being the scalar
curvature), cosmological scenario,beginning at the Planck scale, is obtained.
Here, a unified picture of cosmology is obtained from gravity. In this
scenario, universe begins with power-law inflation, followed by deceleration
and acceleration in the late universe as well as possible collapse of the
universe in future. It is different from dark energy models with
non-linear curvature terms assumed as dark energy. Here, dark energy terms are
induced by linear as well as non-linear terms of curvature in Friedmann
equation being derived from modified gravity.It is also interesting to see
that, in this model, dark radiation and dark matter terms emerge spontaneously
from the gravitational sector. It is found that dark energy, obtained here,
behaves as quintessence in the early universe and phantom in the late universe.
Moreover, analogous to brane-tension in brane-gravity inspired Friedmann
equation, a tension term arises here being called as cosmic tension.
It is found that, in the late universe, Friedmann equation (obtained here)
contains a term ( being the phantom energy density)
analogous to a similar term in Friedmann equation with loop quantum effects, if
and brane-gravity correction when Comment: 19 Pages. To appear in Int. J. Thro. Phy
Applying systems thinking to unravel the mechanisms underlying orthostatic hypotension related fall risk
Orthostatic hypotension (OH) is an established and common cardiovascular risk factor for falls. An in-depth understanding of the various interacting pathophysiological pathways contributing to OH-related falls is essential to guide improvements in diagnostic and treatment opportunities. We applied systems thinking to multidisciplinary map out causal mechanisms and risk factors. For this, we used group model building (GMB) to develop a causal loop diagram (CLD). The GMB was based on the input of experts from multiple domains related to OH and falls and all proposed mechanisms were supported by scientific literature. Our CLD is a conceptual representation of factors involved in OH-related falls, and their interrelatedness. Network analysis and feedback loops were applied to analyze and interpret the CLD, and quantitatively summarize the function and relative importance of the variables. Our CLD contains 50 variables distributed over three intrinsic domains (cerebral, cardiovascular, and musculoskeletal), and an extrinsic domain (e.g., medications). Between the variables, 181 connections and 65 feedback loops were identified. Decreased cerebral blood flow, low blood pressure, impaired baroreflex activity, and physical inactivity were identified as key factors involved in OH-related falls, based on their high centralities. Our CLD reflects the multifactorial pathophysiology of OH-related falls. It enables us to identify key elements, suggesting their potential for new diagnostic and treatment approaches in fall prevention. The interactive online CLD renders it suitable for both research and educational purposes and this CLD is the first step in the development of a computational model for simulating the effects of risk factors on falls
Form Factors from QCD Light-Cone Sum Rules
We derive new QCD sum rules for and form factors. The
underlying correlation functions are expanded near the light-cone in terms of
-meson distribution amplitudes defined in HQET, whereas the -quark mass
is kept finite. The leading-order contributions of two- and three-particle
distribution amplitudes are taken into account. From the resulting light-cone
sum rules we calculate all B\to \Dst form factors in the region of small
momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the
sum rules reduce to a single expression for the Isgur-Wise function. We compare
our predictions with the form factors extracted from experimental B\to \Dst l
\nu_l decay rates fitted to dispersive parameterizations.Comment: 20 pages, 6 figures; one reference, one figure and several comments
added; version to appear in European Physical Journal
The B-Meson Distribution Amplitude in QCD
The B-meson distribution amplitude is calculated using QCD sum rules. In
particular we obtain an estimate for the integral relevant to exclusive
B-decays \lambda_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated
parametrization of the distribution amplitude is suggested.Comment: 17 pages, 8 figures, Latex styl
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