2,264 research outputs found
Recommended from our members
Optimization of Corner Blending Curves
The blending or filleting of sharp corners is a common requirement in geometric design applications â motivated by aesthetic, ergonomic, kinematic, or mechanical stress considerations. Corner blending curves are usually required to exhibit a specified order of geometric continuity with the segments they connect, and to satisfy specific constraints on their curvature profiles and the extremum deviation from the original corner. The free parameters of polynomial corner curves of degree â€6 and continuity up to G3 are exploited to solve a convex optimization problem, that minimizes a weighted sum of dimensionless measures of the mid-point curvature, maximum deviation, and the uniformity of parametric speed. It is found that large mid-point curvature weights result in undesirable bimodal curvature profiles, but emphasizing the parametric speed uniformity typically yields good corner shapes (since the curvature is strongly dependent upon parametric speed variation). A constrained optimization problem, wherein a particular value of the corner curve deviation is specified, is also addressed. Finally, the shape of Pythagorean-hodograph corner curves is compared with that of the optimized âordinaryâ polynomial corner curves
Isogeometric Analysis in advection-diffusion problems: tension splines approximation
We present a novel approach, within the new paradigm of isogeometric analysis
introduced by Hughes et al., to deal with advection dominated
advection-diffusion problems. The key ingredient is the use of Galerkin approximating
spaces of functions with high smoothness, as in IgA based on
classical B-splines, but particularly well suited to describe sharp layers involving
very strong gradients
Construction of planar quintic Pythagorean-hodograph curves by control-polygon constraints
In the construction and analysis of a planar Pythagoreanâhodograph (PH) quintic curve r(t), tâ[0,1] using the complex representation, it is convenient to invoke a translation/rotation/scaling transformation so r(t) is in canonical form with r(0)=0, r(1)=1 and possesses just two complex degrees of freedom. By choosing two of the five controlâpolygon legs of a quintic PH curve as these free complex parameters, the remaining three controlâpolygon legs can be expressed in terms of them and the roots of a quadratic or quartic equation. Consequently, depending on the chosen two controlâpolygon legs, there exist either two or four distinct quintic PH curves that are consistent with them. A comprehensive analysis of all possible pairs of chosen control polygon legs is developed, and examples are provided to illustrate this controlâpolygon paradigm for the construction of planar quintic PH curves
Unfreezing of molecular motions in protein-polymer conjugates: a calorimetric study
Protein-polymer conjugates are a promising class of biohybrids. In this work, the dynamics of a set of biodegradable conjugates myoglobin-poly(ethyl ethylene phosphate) (My-PEEP) with variations in the number of attached polymers and their molar mass in the dry-state, have been investigated to understand the role of polymer on protein dynamics. We performed Differential Scanning Calorimetry measurements between 190 and 300 K, observing the large-scale dynamics arising from reorganization of conformational states, i.e. within the 100 s timescale. The application of an annealing time during the cooling scans was used to investigate the non-equilibrium glassy-state of the samples, observing the relaxation enthalpy at different annealing temperatures. This procedure permitted to extensively describe the transition broadness and the system relaxation kinetics in the glassy state. The samples show an experimental behaviour different from the theoretical predictions, suggesting the establishment of interactions among the protein and the polymer chains. The different behaviour of the conjugates and the physical mixture (composed of the protein and the polymer physically mixed) highlighted the importance of the covalent bond in defining the system dynamics
Evaluation of rice genotypes for resistance to Diatraea saccharalis (Fabricius) using phenotyping methods.
The sugar cane borer, Diatraea saccharalis (Fabricius) is a pest of rice in Brazil and several American countries. An increase in D. saccharalis frequency of occurrence in recent years has emphasized the necessity to develop more effective stem-borer management strategies for the Brazilian rice growers. Control borers with insecticides after larvae penetrate into the rice stalk is difficult. The search for resistance to D. saccharalis is very important to identify source of resistance for breeding programs. Since 2010, we have conducted a series of experiments in greenhouse conditions, to identify genotypes with resistance to borers in the Brazilian rice genebank. The ultimate goal of our study is to use selected accessions as donor parents with the aim to produce rice cultivars with enhanced resistance to sugarcane borer via conventional methods of plant breeding, and in the future, through the use of molecular markers using genetic engineering methods.Editores: Paulo SĂ©rgio de Paula Herrmann Junior, Paulino Ribeiro Villas Boas
The geological record of storm events over the last 1000 years in the Salerno Bay (Southern Tyrrhenian Sea): new proxy evidences
International audienceThe shallow marine Late Holocene wedge of the northern Salerno Bay shelf (Southern Tyrrhenian Sea) discloses the presence of four decimetric shelf-tapering sand beds. Their internal features, depicted by cores analysis and their stratigraphic position, revealed by VHR seismic investigations, inferred sandy layers as being the result of flash deposition, storm controlled, thus episodic. Stratigraphic correlations among cores lead to constrain sandy layers deposition to storm events falling in the 11th, 16th, 19th and 20th centuries. A certain attribution of the most recent event bed to the major cloudburst that hit the Salerno region in 1954A.D. and resulted in a disastrous flood of the Bonea stream, was formerly achieved. A tentative link with two sea-storms that occurred in the 1544A.D. and in the 1879A.D. and well documented by historical sources is here proposed to explain the deposition of the two previous event beds. The deposition of these sandy layers must be related to major storm events, since their preservation in the stratigraphic record is not common. Lithostratigraphic and textural differences between flood and sea-storm emplacement emerge from the study of sandy layers in cores and point to a prevalence of sea-storm deposits in the middle shelf compared to flood deposits. Seismic stratigraphic evidence lead us to suppose that the style of episodic flash deposition has been running on for the last 2-3kyr and is probably linked to a climatic trend of the region
Neuroendocrine tumour arising inside a retro-rectal tailgut cyst: report of two cases and a review of the literature
Tailgut cysts (or retro-rectal cyst-hamartomas (RCHs)) are developmental abnormalities consisting of multiloculated cysts lined by squamous, transitional or glandular epithelium which, albeit rarely, may give rise to malignant transformations. Carcinoid tumours arising in the presacral region are extremely rare and usually benign, and only a few are described in the literature. Case 1: A 63-year-old female diagnosed as having bilateral ovarian cysts underwent surgery to remove a right adnexial mass that was histopathologically diagnosed as a well-differentiated carcinoid tumour. She is currently disease free after 18 months of follow-up. Case 2: A 41-year-old-female diagnosed with hepatic metastases and a solid pelvic mass arising from a moderately differentiated neuroendocrine carcinoma is currently alive with disease after having undergone surgical removal of the mass and several medical treatments. We here describe two different clinical histories of well- and moderately differentiated neuroendocrine tumours (NETs) arising from tailgut cysts in the prerectal space together with a review of the relevant literature
A comparison between standard and crossfeed monopulse radars in presence of rough sea scattering and ship movements
Monopulse radars are widely used in tracking systems, due to their relative
simplicity and theoretical precision, but the presence of multipath
impairs the tracking capabilities of these radars, especially when multipath
signals are strong, as in a naval environment. A special monopulse
setup, the crossfeed, has been proposed in the past to provide an automatic
cancellation from smooth sea multipath. In this contribution,
the performances of such a system are analyzed in presence of rough sea
scattering and compared with those of a standard monopulse setup. Particular
attention is devoted to performance degradations due to possible
phase errors in the passive network implementing the comparator and
due to ship rolling and pitching. This latter requires a full 3D monopulse
simulator for its correct evaluation
- âŠ