642 research outputs found
Partial Degree Formulae for Plane Offset Curves
In this paper we present several formulae for computing the partial degrees
of the defining polynomial of the offset curve to an irreducible affine plane
curve given implicitly, and we see how these formulae particularize to the case
of rational curves. In addition, we present a formula for computing the degree
w.r.t the distance variable.Comment: 24 pages, no figure
Business Marketing Tips Pecel Lele Tent Shop All the Way of Cross North Sumatra Lirik District Indragiri Hulu Regency Riau Province
This research on pecel lele business marketing tips in the tent stalls and was held on 17 June to 3 July 2015 along the East Sumatera Lirik District of Indragiri Hulu Regency Riau province. The purpose of this study was to describe the business activities pecel lele in the tent stalls and separately describe the factors that influence marketing efforts in the shop tent pecel lele. The method used in this study is a survey method.The results showed that the tent stalls pecel lele is a trading business meal is done in the afternoon until midnight and even some are open at 17:00 pm until 24.00 pm which amounted to 6 waung pecel lele, while the business is located near the dismissal of intercity public transport this province which amounted to 3 stalls open at 15:00 pm until 3:00 pm, because the location is always crowded prospective buyers. The existence of business pecel lele by employers pecel lele in the Trans Eastern Sumatra District of Lirik Indragiri Hulu influenced by some external factors: the probability that the rate of population growth, innovation cookware, policies and government\u27s role in business development pecel lele, where location support, availability raw materials, consumer purchasing power, the development of the marketing area. Internal factors are the factors by an employer to conduct business activities tent stalls pecel lele. the results of research conducted by the tips of respondents different merchants, among them there maid, facilities, strategic location, quality of product, service / service and cleanliness
Continuum viscoplastic simulation of a granular column collapse on large slopes: Îź(I) rheology and lateral wall effects
We simulate here dry granular flows resulting from the collapse of granular columns on an inclined channel (up to 22°) and compare precisely the results with laboratory experiments. Incompressibility is assumed despite the dilatancy observed in the experiments (up to 10%). The 2-D model is based on the so-called Îź(I) rheology that induces a Drucker-Prager yield stress and a variable viscosity. A nonlinear Coulomb friction term, representing the friction on the lateral walls of the channel, is added to the model. We demonstrate that this term is crucial to accurately reproduce granular collapses on slopes âł10°, whereas it remains of little effect on the horizontal slope. Quantitative comparison between the experimental and numerical changes with time of the thickness profiles and front velocity makes it possible to strongly constrain the rheology. In particular, we show that the use of a variable or a constant viscosity does not change significantly the results provided that these viscosities are of the same order. However, only a fine tuning of the constant viscosity (Ρ=1 Pa s) makes it possible to predict the slow propagation phase observed experimentally at large slopes. Finally, we observed that small-scale instabilities develop when refining the mesh (also called ill-posed behavior, characterized in the work of Barker et al. [âWell-posed and ill-posed behaviour of the Îź(I)-rheology for granular flow,â J. Fluid Mech. 779, 794â818 (2015)] and in the present work) associated with the mechanical model. The velocity field becomes stratified and the bands of high velocity gradient appear. These model instabilities are not avoided by using variable viscosity models such as the Îź(I) rheology. However we show that the velocity range, the static-flowing transition, and the thickness profiles are almost not affected by them
Comparing faceted and smoothed tool surface descriptions in sheet metal forming simulation
This study deals with different tool surface description
methods used in the finite element analysis of sheet metal
forming processes. The description of arbitrarily-shaped tool
surfaces using the traditional linear finite elements is compared
with two distinct smooth surface description approaches:
(i) BĂŠzier patches obtained from the ComputerAided
Design model and (ii) smoothing the finite element
mesh using Nagata patches. The contact search algorithm is
presented for each approach, exploiting its special features in
order to ensure an accurate and efficient contact detection. The
influence of the tool modelling accuracy on the numerical
results is analysed using two sheet forming examples, the
unconstrained cylindrical bending and the reverse deep drawing
of a cylindrical cup. Smoothing the contact surfaces with
Nagata patches allows creating more accurate tool models,
both in terms of shape and normal vectors, when compared
with the conventional linear finite element mesh. The computational
efficiency is evaluated in this study through the total
number of increments and the required CPU time. The mesh
refinement in the faceted description approach is not effective
in terms of computational efficiency due to large discontinuities
in the normal vector field across facets, even when
adopting fine meshes.The authors gratefully acknowledge the financial
support of the Portuguese Foundation for Science and Technology (FCT)
via the projects PTDC/EME-TME/118420/2010 and PEst-C/EME/
UI0285/2013 and by FEDER funds through the program COMPETE â
Programa Operacional Factores de Competitividade, under the project
CENTRO-07-0224-FEDER-002001 (MT4MOBI). The first author is
also grateful to the FCT for the PhD grant SFRH/BD/69140/2010.info:eu-repo/semantics/publishedVersio
A survey of partial differential equations in geometric design
YesComputer aided geometric design is an area
where the improvement of surface generation techniques
is an everlasting demand since faster and more accurate
geometric models are required. Traditional methods
for generating surfaces were initially mainly based
upon interpolation algorithms. Recently, partial differential
equations (PDE) were introduced as a valuable
tool for geometric modelling since they offer a number
of features from which these areas can benefit. This work
summarises the uses given to PDE surfaces as a surface
generation technique togethe
A study on spline quasi-interpolation based quadrature rules for the isogeometric Galerkin BEM
Two recently introduced quadrature schemes for weakly singular integrals
[Calabr\`o et al. J. Comput. Appl. Math. 2018] are investigated in the context
of boundary integral equations arising in the isogeometric formulation of
Galerkin Boundary Element Method (BEM). In the first scheme, the regular part
of the integrand is approximated by a suitable quasi--interpolation spline. In
the second scheme the regular part is approximated by a product of two spline
functions. The two schemes are tested and compared against other standard and
novel methods available in literature to evaluate different types of integrals
arising in the Galerkin formulation. Numerical tests reveal that under
reasonable assumptions the second scheme convergences with the optimal order in
the Galerkin method, when performing -refinement, even with a small amount
of quadrature nodes. The quadrature schemes are validated also in numerical
examples to solve 2D Laplace problems with Dirichlet boundary conditions
Concern with COVID-19 Pandemic Threat and Attitudes Towards Immigrants:The Mediating Effect of the Desire for Tightness
Tightening social norms is thought to be adaptive for dealing with collective threat yet it may have negative consequences for increasing prejudice. The present research investigated the role of desire for cultural tightness, triggered by the COVID-19 pandemic, in increasing negative attitudes towards immigrants. We used participant-level data from 41 countries (NâŻ=âŻ55,015) collected as part of the PsyCorona project, a cross-national longitudinal study on responses to COVID-19. Our predictions were tested through multilevel and SEM models, treating participants as nested within countries. Results showed that people's concern with COVID-19 threat was related to greater desire for tightness which, in turn, was linked to more negative attitudes towards immigrants. These findings were followed up with a longitudinal model (NâŻ=âŻ2,349) which also showed that people's heightened concern with COVID-19 in an earlier stage of the pandemic was associated with an increase in their desire for tightness and negative attitudes towards immigrants later in time. Our findings offer insight into the trade-offs that tightening social norms under collective threat has for human groups
New method to find corner and tangent vertices in sketches using parametric cubic curves approximation
Some recent approaches have been presented as simple and highly accurate corner finders in the sketches including curves, which is useful to support natural human-computer interaction, but these in most cases do not consider tangent vertices (smooth points between two geometric entities, present in engineering models), what implies an important drawback in the field of design. In this article we present a robust approach based on the approximation to parametric cubic curves of the stroke for further radius function calculation in order to detect corner and tangent vertices. We have called our approach Tangent and Corner Vertices Detection (TCVD), and it works in the following way. First, corner vertices are obtained as minimum radius peaks in the discrete radius function, where radius is obtained from differences. Second, approximated piecewise parametric curves on the stroke are obtained and the analytic radius function is calculated. Then, curves are obtained from stretches of the stroke that have a small radius. Finally, the tangent vertices are found between straight lines and curves or between curves, where no corner vertices are previously located. The radius function to obtain curves is calculated from approximated piecewise curves, which is much more noise free than discrete radius calculation. Several tests have been carried out to compare our approach to that of the current best benchmarked, and the obtained results show that our approach achieves a significant accuracy even better finding corner vertices, and moreover, tangent vertices are detected with an Accuracy near to 92% and a False Positive Rate near to 2%.Spanish Ministry of Science and Education and the FEDER Funds, through CUESKETCH (Ref. DPI2007-66755-C02-01) and HYMAS projects (Ref. DPI2010-19457) partially supported this work.Albert Gil, FE.; GarcĂa FernĂĄndez-Pacheco, D.; Aleixos BorrĂĄs, MN. (2013). New method to find corner and tangent vertices in sketches using parametric cubic curves approximation. Pattern Recognition. 46(5):1433-1448. https://doi.org/10.1016/j.patcog.2012.11.006S1433144846
Seasonal changes in patterns of gene expression in avian song control brain regions.
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Photoperiod and hormonal cues drive dramatic seasonal changes in structure and function of the avian song control system. Little is known, however, about the patterns of gene expression associated with seasonal changes. Here we address this issue by altering the hormonal and photoperiodic conditions in seasonally-breeding Gambel's white-crowned sparrows and extracting RNA from the telencephalic song control nuclei HVC and RA across multiple time points that capture different stages of growth and regression. We chose HVC and RA because while both nuclei change in volume across seasons, the cellular mechanisms underlying these changes differ. We thus hypothesized that different genes would be expressed between HVC and RA. We tested this by using the extracted RNA to perform a cDNA microarray hybridization developed by the SoNG initiative. We then validated these results using qRT-PCR. We found that 363 genes varied by more than 1.5 fold (>log(2) 0.585) in expression in HVC and/or RA. Supporting our hypothesis, only 59 of these 363 genes were found to vary in both nuclei, while 132 gene expression changes were HVC specific and 172 were RA specific. We then assigned many of these genes to functional categories relevant to the different mechanisms underlying seasonal change in HVC and RA, including neurogenesis, apoptosis, cell growth, dendrite arborization and axonal growth, angiogenesis, endocrinology, growth factors, and electrophysiology. This revealed categorical differences in the kinds of genes regulated in HVC and RA. These results show that different molecular programs underlie seasonal changes in HVC and RA, and that gene expression is time specific across different reproductive conditions. Our results provide insights into the complex molecular pathways that underlie adult neural plasticity
- âŚ