5,681 research outputs found
A novel updating modelling methodology for free-form surface modifications in the early stages of design
The paper describes the first implementation of a method in which an initial CAD model is updated from a physical model. The method is based on image-mapping in which an initial CAD model is updated from images of a soft rapid prototype model (RPM) which has been sculpted in order to carry out formal developments. The RP model is made by a 3Dimensional-colour printer, has a built-in contrasting grid composed by parallel planes in the X, Y and/or Z co-ordinates and has special consistency allowing it to be easily sculpted with hand modifications. During the sculpting process changes on the surface affect the lines on the RPM, which are the external presence of the internal grid planes and are corresponding to the initial CAD construction lines. These lines (profiles) then are visually contrasted by making use of identical perspective transformations and viewpoints for the virtual model and the RP model image. The initial CAD model is then updated by modifying the surface’s
construction lines to match the lines on the RP image by moving control points, such as in the Z direction
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Use of 3D body motion to freeform surface design
This paper presents a novel surface modelling approach by utilising a 3D motion capture system. For designing a large-sized surface, a network of splines is initially set up. Artists or designers wearing motion markers on their hands can then change shapes of the splines with their hands. Literarily they can move their bodies freely to any positions to perform their tasks. They can also move their hands in 3D free space to detail surface characteristics by their gestures. All their design motions are recorded in the motion capturing system and transferred into 3D curves and surfaces correspondingly. This paper reports this novel surface design method and some case studies
The utility of wide-field optical coherence tomography angiography in diagnosis and monitoring of proliferative diabetic retinopathy in pregnancy
Purpose: Diabetic retinopathy is an increasingly common complication of diabetes mellitus that benefits from early diagnosis and frequent monitoring, especially in pregnancy where there is a greater risk of progression. Fundus fluorescein angiography is currently the gold standard method of investigation for neovascularization. However, this has risks of unpleasant and potentially dangerous side effects, with an added theoretical risk to the fetus in pregnancy. Wide-field optical coherence tomography angiography (PLEX Elite 9000, Carl Zeiss Meditec, Inc. USA and DRI Swept Source OCT Triton, Topcon Medical Systems, Inc. USA) potentially offers a safer, faster and equally effective alternative method for diagnosis and monitoring of diabetic retinopathy in pregnant patients. Observations: In the 3 cases reviewed from our clinic, we found that wide-field optical coherence tomography angiography was successfully used as an alternative to fundus fluorescein angiography in early diagnosis and ongoing monitoring of diabetic retinopathy in pregnant patients. Conclusions and importance: Wide-field optical coherence tomography angiography can be considered as a useful alternative to fundus fluorescein angiography when reviewing pregnant diabetic retinopathy patients. This allows avoidance of any unpleasant and potentially dangerous side effects associated with fluorescein injection, and appears to be just as effective in diagnosis and detecting disease progression
Correlates of genetic monogamy in socially monogamous mammals: insights from Azara's owl monkeys
Understanding the evolution of mating systems, a central topic in evolutionary biology for more than 50 years, requires examining the genetic consequences of mating and the relationships between social systems and mating systems. Among pair-living mammals, where genetic monogamy is extremely rare, the extent of extra-group paternity rates has been associated withmale participation in infant care, strength of the pair bond and length of the breeding season. This study evaluated the relationship between two of those factors and the genetic mating system of socially monogamous mammals, testing predictions that male care and strength of pair bond would be negatively correlated with rates of extra-pair paternity (EPP). Autosomal microsatellite analyses provide evidence for genetic monogamy in a pair-living primate with bi-parental care, the Azara’s owl monkey (Aotus azarae). A phylogenetically corrected generalized least square analysis was used to relate male care and strength of the pair bond to their genetic mating system (i.e. proportions of EPP) in 15 socially monogamous mammalian species. The intensity of male care was correlated with EPP rates in mammals, while strength of pair bond failed to reach statistical significance. Our analyses showthat, once social monogamy has evolved, paternal care, and potentially also close bonds, may facilitate the evolution of genetic monogamy.German Science Foundation (HU 1746/2-1); Wenner-Gren Foundation; L.S.B. Leakey Foundation;National Geographic Society; National Science Foundation
(BCS-0621020, 1219368, and 1232349); the University of Pennsylvania Research Foundation; the Zoological Society of San Dieg
Multimode morphodynamic model for sediment-laden flows and geomorphic impacts
Sediment-laden flows are a complex solid-fluid interaction process. This study presents a multimode morphodynamic model system combined with shallow water theory and a nonequilibrium assumption for sediment transport. The model system aims to simulate the morphological change caused by sediment-laden flows with various sediment transport modes. It involves three modules: a hydrodynamic module, a sediment transport module, and a morphological evolution module. The hydrodynamic model is governed by modified shallow water equations considering the interaction effects of flow and sediment. A flexible sediment transport model is presented that incorporates a weight coefficient. The model can adaptively choose an appropriate transport mode according to local, real-time flow conditions. Bedload, suspended load, and total mixed sediment load are all involved. The model is solved by a second-order Godunov-type finite-volume method that is robust and accurate. Validation is demonstrated through a series of test cases. The results indicate that the model can attain good agreement with measured data, thereby demonstrating the capabilities of the multimode morphodynamic model system in predicting sediment-laden flows and resulting morphological change
Microstructural characterization of AISI 431 martensitic stainless steel laser-deposited coatings
High cooling rates during laser cladding of stainless steels may alter the microstructure and phase constitution of the claddings and consequently change their functional properties. In this research, solidification structures and solid state phase transformation products in single and multi layer AISI 431 martensitic stainless steel coatings deposited by laser cladding at different processing speeds are investigated by optical microscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), orientation imaging microscopy (OIM), ternary phase diagram, Schaeffler and TTT diagrams. The results of this study show how partitionless solidification and higher solidification rates alter the microstructure and phase constitution of martensitic stainless steel laser deposited coatings. In addition, it is shown that while different cladding speeds have no effect on austenite–martensite orientation relationship in the coatings, increasing the cladding speed has resulted in a reduction of hardness in deposited coatings which is in contrast to the common idea about obtaining higher hardness values at higher cladding speeds.
Evidence of Andreev bound states as a hallmark of the FFLO phase in -(BEDT-TTF)Cu(NCS)
Superconductivity is a quantum phenomena arising, in its simplest form, from
pairing of fermions with opposite spin into a state with zero net momentum.
Whether superconductivity can occur in fermionic systems with unequal number of
two species distinguished by spin, atomic hyperfine states, flavor, presents an
important open question in condensed matter, cold atoms, and quantum
chromodynamics, physics. In the former case the imbalance between spin-up and
spin-down electrons forming the Cooper pairs is indyced by the magnetic field.
Nearly fifty years ago Fulde, Ferrell, Larkin and Ovchinnikov (FFLO) proposed
that such imbalanced system can lead to exotic superconductivity in which pairs
acquire finite momentum. The finite pair momentum leads to spatially
inhomogeneous state consisting of of a periodic alternation of "normal" and
"superconducting" regions. Here, we report nuclear magnetic resonance (NMR)
measurements providing microscopic evidence for the existence of this new
superconducting state through the observation of spin-polarized quasiparticles
forming so-called Andreev bound states.Comment: 6 pages, 5 fig
Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO2 adsorption
Funding: EPSRCThe structure of dehydrated calcined ECR-18, synthetic paulingite, topology type PAU, unit cell composition Na132H28Si512Al160O1344, has been determined by Rietveld refinement against synchrotron X-ray powder diffraction data. Upon dehydration the symmetry of Na,H-ECR-18 changes from Im3m to I 43m, with a corresponding decrease of cubic unit cell a parameter from 34.89412(1) A to 33.3488(3) A. This occurs as the framework distorts to afford closer coordination of Na+ cations by framework O atoms in 8-ring window sites of the seven cage types present. Na+ cations in 8R sites block the access of N2 molecules to the internal pore space at 77 K but CO2 adsorption at 308 K is observed, and is postulated to occur via a 'trapdoor' mechanism. In situ PXRD during CO2 adsorption at pressures up to 10 bar show reversible broadening of diffraction peaks that is attributed to local crystallographic strain.Publisher PDFPeer reviewe
Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons
Fundamental interactions induced by lattice vibrations on ultrafast time
scales become increasingly important for modern nanoscience and technology.
Experimental access to the physical properties of acoustic phonons in the THz
frequency range and over the entire Brillouin zone is crucial for understanding
electric and thermal transport in solids and their compounds. Here, we report
on the generation and nonlinear propagation of giant (1 percent) acoustic
strain pulses in hybrid gold/cobalt bilayer structures probed with ultrafast
surface plasmon interferometry. This new technique allows for unambiguous
characterization of arbitrary ultrafast acoustic transients. The giant acoustic
pulses experience substantial nonlinear reshaping already after a propagation
distance of 100 nm in a crystalline gold layer. Excellent agreement with the
Korteveg-de Vries model points to future quantitative nonlinear femtosecond
THz-ultrasonics at the nano-scale in metals at room temperature
Stellar winds from Massive Stars
We review the various techniques through which wind properties of massive
stars - O stars, AB supergiants, Luminous Blue Variables (LBVs), Wolf-Rayet
(WR) stars and cool supergiants - are derived. The wind momentum-luminosity
relation (e.g. Kudritzki et al. 1999) provides a method of predicting mass-loss
rates of O stars and blue supergiants which is superior to previous
parameterizations. Assuming the theoretical sqrt(Z) metallicity dependence,
Magellanic Cloud O star mass-loss rates are typically matched to within a
factor of two for various calibrations. Stellar winds from LBVs are typically
denser and slower than equivalent B supergiants, with exceptional mass-loss
rates during giant eruptions Mdot=10^-3 .. 10^-1 Mo/yr (Drissen et al. 2001).
Recent mass-loss rates for Galactic WR stars indicate a downward revision of
2-4 relative to previous calibrations due to clumping (e.g. Schmutz 1997),
although evidence for a metallicity dependence remains inconclusive (Crowther
2000). Mass-loss properties of luminous (> 10^5 Lo) yellow and red supergiants
from alternative techniques remain highly contradictory. Recent Galactic and
LMC results for RSG reveal a large scatter such that typical mass-loss rates
lie in the range 10^-6 .. 10^-4 Mo/yr, with a few cases exhibiting 10^-3 Mo/yr.Comment: 16 pages, 2 figures, Review paper to appear in Proc `The influence of
binaries on stellar population studies', Brussels, Aug 2000 (D. Vanbeveren
ed.), Kluwe
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