1,087 research outputs found
Counting function for a sphere of anisotropic quartz
We calculate the leading Weyl term of the counting function for a
mono-crystalline quartz sphere. In contrast to other studies of counting
functions, the anisotropy of quartz is a crucial element in our investigation.
Hence, we do not obtain a simple analytical form, but we carry out a numerical
evaluation. To this end we employ the Radon transform representation of the
Green's function. We compare our result to a previously measured unique data
set of several tens of thousands of resonances.Comment: 16 pages, 11 figure
Highly Dispersive Electron Relaxation and Colossal Thermoelectricity in the Correlated Semiconductor FeSb
We show that the colossal thermoelectric power, , observed in the
correlated semiconductor FeSb below 30\,K is accompanied by a huge Nernst
coefficient and magnetoresistance MR. Markedly, the latter two
quantities are enhanced in a strikingly similar manner. While in the same
temperature range, of the reference compound FeAs, which has a
seven-times larger energy gap, amounts to nearly half of that of FeSb, its
and MR are intrinsically different to FeSb: they are smaller
by two orders of magnitude and have no common features. With the charge
transport of FeAs successfully captured by the density functional theory,
we emphasize a significantly dispersive electron-relaxation time
due to electron-electron correlations to be at the heart of
the peculiar thermoelectricity and magnetoresistance of FeSb.Comment: 8 pages, 5 figure
Collision of One-Dimensional Nonlinear Chains
We investigate one-dimensional collisions of unharmonic chains and a rigid
wall. We find that the coefficient of restitution (COR) is strongly dependent
on the velocity of colliding chains and has a minimum value at a certain
velocity. The relationship between COR and collision velocity is derived for
low-velocity collisions using perturbation methods. We found that the velocity
dependence is characterized by the exponent of the lowest unharmonic term of
interparticle potential energy
A study of the fine scale motions of incompressible time-developing mixing layers
This work is an extension of a project conducted at the previous CTR summer program and was reported by Chen et al. (1990). In that program, the geometry and topology of the dissipating motions in a variety of shear flows was examined. All data was produced by direct numerical simulations (DNS). The partial derivatives of the velocity field were determined at every grid point in the flow and various invariants and related quantities were computed from the velocity gradient tensor. Motions characterized by high rates of kinetic energy dissipation and high enstrophy were of particular interest. Scatter diagrams of the invariants were mapped out and interesting and unexpected patterns were seen. Each type of shear layer produced its own characteristic scatter plot. In the present project, attention is focused on the incompressible plane mixing layer, and the scatter diagrams are replaced with more useful joint probability density contours. Comparison of the topology of the dissipating motions of flows at different Reynolds numbers are made. Also, plane mixing layers at the same Reynolds number but with different initial conditions are compared
ATscale – Establishing a Cross-Sector Partnership to Increase Access to Assistive Technology
Given existing gaps in access to Assistive Technology (AT) globally, it is important to think broadly
and identify innovative approaches to overcome them. After an initial scoping in 2018, involving
consultations and landscape analyses, ATscale, the Global Partnership for Assistive Technology was
launched at the Global Disability Summit in July 2018 with the aim of reaching 500 million more
people with life-changing AT by 2030. Applying lessons-learned from other areas of global health
and development, ATscale was established with the recognition that to influence the complex
systems for AT access, a broad set of stakeholders is needed to invest in and coordinate a multifaceted, systematic approach spanning market shaping, capacity development, and political
prioritisation.
Already, ATscale has demonstrated how a multi-sector group can come together and develop a
cohesive strategy. This strategy overview has been released and shared broadly for additional
consultation and feedback to further refine ATscale’s approach moving forward. ATscale has
captured the attention of a diverse set of stakeholders. It now has eleven organisations within the
Forming Committee and a broad community willing to inform its development. Now that it has been
established, ATscale is working to move from an initial forming phase to a more formal organisation
and to refine its operating model by late 2019 or early 2020.
While there is significant momentum towards taking new, innovative approaches to address the
gaps in access to quality, affordable AT for all, research shows that a wide range of systemic,
underlying barriers and cross-cutting factors are contributing to the challenge in matching
appropriate supply and demand for AT. While ATscale will address many of these, it is also going to
require partnership on multiple levels with a coordinated strategic approach across a variety of
stakeholders. This collective effort will enable the global community to have an impact greater than
the sum of its individual parts in improving access to affordable, appropriate AT globally
Analyzing Array Manipulating Programs by Program Transformation
We explore a transformational approach to the problem of verifying simple array-manipulating programs. Traditionally, verification of such programs requires intricate analysis machinery to reason with universally quantified statements about symbolic array segments, such as "every data item stored in the segment A[i] to A[j] is equal to the corresponding item stored in the segment B[i] to B[j]." We define a simple abstract machine which allows for set-valued variables and we show how to translate programs with array operations to array-free code for this machine. For the purpose of program analysis, the translated program remains faithful to the semantics of array manipulation. Based on our implementation in LLVM, we evaluate the approach with respect to its ability to extract useful invariants and the cost in terms of code size
Percutaneous transfemoral-transseptal implantation of a second-generation CardiAQâ„¢ mitral valve bioprosthesis: first procedure description and 30-day follow-up
Transcatheter mitral valve implantation for mitral valve regurgitation is in the very early phase of development because of challenging anatomy and device dimensions. We describe the procedure of a transfemoral-transseptal implantation of the second-generation CardiAQâ„¢ mitral valve bioprosthesis and 30-day follow-up
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