12,729 research outputs found
Outflow boundary conditions for 3D simulations of non-periodic blood flow and pressure fields in deformable arteries
The simulation of blood flow and pressure in arteries requires outflow
boundary conditions that incorporate models of downstream domains. We
previously described a coupled multidomain method to couple analytical models
of the downstream domains with 3D numerical models of the upstream vasculature.
This prior work either included pure resistance boundary conditions or
impedance boundary conditions based on assumed periodicity of the solution.
However, flow and pressure in arteries are not necessarily periodic in time due
to heart rate variability, respiration, complex transitional flow or acute
physiological changes. We present herein an approach for prescribing lumped
parameter outflow boundary conditions that accommodate transient phenomena. We
have applied this method to compute haemodynamic quantities in different
physiologically relevant cardiovascular models, including patient-specific
examples, to study non-periodic flow phenomena often observed in normal
subjects and in patients with acquired or congenital cardiovascular disease.
The relevance of using boundary conditions that accommodate transient phenomena
compared with boundary conditions that assume periodicity of the solution is
discussed
Spectrally resolved single-shot wavefront sensing of broadband high-harmonic sources
Wavefront sensors are an important tool to characterize coherent beams of
extreme ultraviolet radiation. However, conventional Hartmann-type sensors do
not allow for independent wavefront characterization of different spectral
components that may be present in a beam, which limits their applicability for
intrinsically broadband high-harmonic generation (HHG) sources. Here we
introduce a wavefront sensor that measures the wavefronts of all the harmonics
in a HHG beam in a single camera exposure. By replacing the mask apertures with
transmission gratings at different orientations, we simultaneously detect
harmonic wavefronts and spectra, and obtain sensitivity to spatiotemporal
structure such as pulse front tilt as well. We demonstrate the capabilities of
the sensor through a parallel measurement of the wavefronts of 9 harmonics in a
wavelength range between 25 and 49 nm, with up to lambda/32 precision.Comment: 12 pages, 6 figure
Finite Element Flow Simulations of the EUROLIFT DLR-F11 High Lift Configuration
This paper presents flow simulation results of the EUROLIFT DLR-F11
multi-element wing configuration, obtained with a highly scalable finite
element solver, PHASTA. This work was accomplished as a part of the 2nd high
lift prediction workshop. In-house meshes were constructed with increasing mesh
density for analysis. A solution adaptive approach was used as an alternative
and its effectiveness was studied by comparing its results with the ones
obtained with other meshes. Comparisons between the numerical solution obtained
with unsteady RANS turbulence model and available experimental results are
provided for verification and discussion. Based on the observations, future
direction for adaptive research and simulations with higher fidelity turbulence
models is outlined.Comment: 52nd Aerospace Sciences Meetin
Phonon-drag induced suppression of the Andreev hole current in superconducting niobium contacts
We have investigated how the Andreev-reflection hole current at ballistic
point contacts responds to a large bias voltage. Its strong suppression could
be explained by the drag excerted by the non-equilibrium phonon wind generated
by high-energy electrons flowing through the contact. The hole - phonon
interaction leads to scattering lengths of the low-energetic holes down to
100\,nm, thereby destroying the coherent retracing of the electron path by the
Andreev-reflected holes.Comment: 7 pages, 4 figures, submitted to Proceedings 26th International
Conference on Low Temperature Physic
Atomic quasi-Bragg diffraction in a magnetic field
We report on a new technique to split an atomic beam coherently with an
easily adjustable splitting angle. In our experiment metastable helium atoms in
the |{1s2s}^3S_1 M=1> state diffract from a polarization gradient light field
formed by counterpropagating \sigma^+ and \sigma^- polarized laser beams in the
presence of a homogeneous magnetic field. In the near-adiabatic regime, energy
conservation allows the resonant exchange between magnetic energy and kinetic
energy. As a consequence, symmetric diffraction of |M=0> or |M=-1> atoms in a
single order is achieved, where the order can be chosen freely by tuning the
magnetic field. We present experimental results up to 6th order diffraction (24
\hbar k momentum splitting, i.e., 2.21 m/s in transverse velocity) and present
a simple theoretical model that stresses the similarity with conventional Bragg
scattering. The resulting device constitutes a flexible, adjustable,
large-angle, three-way coherent atomic beam splitter with many potential
applications in atom optics and atom interferometry.Comment: 4 pages, 5 figure
Exploring the phase structure of lattice QCD with twisted mass quarks
The phase structure of zero temperature twisted mass lattice QCD is
investigated. We find strong metastabilities in the plaquette observable when
the untwisted quark mass sweeps across zero.Comment: Talks presented at Lattice2004(spectrum), 6 pages, 6 figure
ANALISIS DAMPAK LALU LINTAS AKIBAT ADANYA KAWASAN LION HOTEL MANADO TERHADAP KINERJA RUAS JALAN PIERE TENDEAN
Lion Hotel Manado terletak dikawasan pusat kota Manado yang memiliki luas ± 26.782 m2. Sesuai dengan amanat dalam Peraturan Menteri Perhubungan Republik Indonesia Nomor 75 Tahun 2015 tentang Penyelenggaraan Analisis Dampak Lalu Lintas sehingga diwajibkan bagi pengembang kawasan Lion Hotel and Plaza Manado yaitu PT. Lion International Hotel untuk melakukan Analisis Dampak Lalu Lintas di Lion Hotel Manado, juga sesuai dengan Pedoman Teknis Analisis Dampak Lalulintas Pembangunan Pusat Kegiatan pada Ruas Jalan Nasional di Wilayah Perkotaan (2009) yang menyatakan bahwa pusat kegiatan seperti hotel dan pertokoan dengan luas minimal 500 m2 wajib melakukan andalalin. Analisis dampak lalu lintas (Andalalin) adalah kajian yang menilai dampak yang ditimbulkan akibat pengembangan tata guna lahan terhadap sistem pergerakan lalu lintas pada suatu ruas jalan terhadap jaringan transportasi sekitarnya.Penelitian analisis dampak lalu lintas ini dilakukan di kawasan Lion Hotel Manado, Provinsi Sulawesi Utara. Daerah survey meliputi Jl. Piere Tendean, Jl. Ahmad Yani 24, Jl. Bethesda-Wolter Monginsidi, Jl. Wolter Monginsidi depan Transmart Bahu, simpang tidak bersinyal Jl. Piere Tendean. Analisis dilakukan terhadap kinerja ruas jalan dan kinerja persimpangan, analisis penanganan dampak lalulintas, dan analisis penataan eksternal Lion Hotel Manado. Analisis kinerja ruas jalan dan persimpangan mengikuti Pedoman Kapasitas Jalan Indonesia 2014 (PKJI 2014) dengan nilai VCR (Volume Capacity Ratio) atau DS (Degree of saturation) sebagai parameter kinerja.Hasil perhitungan menunjukkan bahwa kinerja persimpangan yang ada dikawasan Lion Hotel Manado berada pada keadaan yang baik dengan DS untuk simpang pertama dan simpang kedua berturut-turut adalah 0,26 dan 0,6. Kapasitas (C) untuk simpang pertama adalah 23.906 dan untuk simpang kedua adalah 7.559. Karena arus lalulintas disimpang yang tidak melebihi kapasitas yang dihitung maka kondisi dari simpang yang ada disekitar kawasan Lion Hotel Manado berada dalam kondisi baik dan tidak ada gangguan akibat adanya kawasan Lion Hotel Manado. Kata Kunci: andalalin, volume capacity ratio, kecepatan, kapasitas, kinerja, persimpanga
Chloroplast DNA rearrangements in Campanulaceae: phylogenetic utility of highly rearranged genomes
BACKGROUND: The Campanulaceae (the "hare bell" or "bellflower" family) is a derived angiosperm family comprised of about 600 species treated in 35 to 55 genera. Taxonomic treatments vary widely and little phylogenetic work has been done in the family. Gene order in the chloroplast genome usually varies little among vascular plants. However, chloroplast genomes of Campanulaceae represent an exception and phylogenetic analyses solely based on chloroplast rearrangement characters support a reasonably well-resolved tree. RESULTS: Chloroplast DNA physical maps were constructed for eighteen representatives of the family. So many gene order changes have occurred among the genomes that characterizing individual mutational events was not always possible. Therefore, we examined different, novel scoring methods to prepare data matrices for cladistic analysis. These approaches yielded largely congruent results but varied in amounts of resolution and homoplasy. The strongly supported nodes were common to all gene order analyses as well as to parallel analyses based on ITS and rbcL sequence data. The results suggest some interesting and unexpected intrafamilial relationships. For example fifteen of the taxa form a derived clade; whereas the remaining three taxa â Platycodon, Codonopsis, and Cyananthus â form the basal clade. This major subdivision of the family corresponds to the distribution of pollen morphology characteristics but is not compatible with previous taxonomic treatments. CONCLUSIONS: Our use of gene order data in the Campanulaceae provides the most highly resolved phylogeny as yet developed for a plant family using only cpDNA rearrangements. The gene order data showed markedly less homoplasy than sequence data for the same taxa but did not resolve quite as many nodes. The rearrangement characters, though relatively few in number, support robust and meaningful phylogenetic hypotheses and provide new insights into evolutionary relationships within the Campanulaceae
Statistics of Certain Models of Evolution
In a recent paper, Newman surveys the literature on power law spectra in
evolution, self-organised criticality and presents a model of his own to arrive
at a conclusion that self-organised criticality is not necessary for evolution.
Not only did he miss a key model (Ecolab) that has a clear self-organised
critical mechanism, but also Newman's model exhibits the same mechanism that
gives rise to power law behaviour as does Ecolab. Newman's model is, in fact, a
``mean field'' approximation of a self-organised critical system. In this
paper, I have also implemented Newman's model using the Ecolab software,
removing the restriction that the number of species remains constant. It turns
out that the requirement of constant species number is non-trivial, leading to
a global coupling between species that is similar in effect to the species
interactions seen in Ecolab. In fact, the model must self-organise to a state
where the long time average of speciations balances that of the extinctions,
otherwise the system either collapses or explodes. In view of this, Newman's
model does not provide the hoped-for counter example to the presence of
self-organised criticality in evolution, but does provide a simple, almost
analytic model that can used to understand more intricate models such as
Ecolab.Comment: accepted in Phys Rev E.; RevTeX; See
http://parallel.hpc.unsw.edu.au/rks/ecolab.html for more informatio
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