Search results for "RAV"

Inflection points and topology of surfaces in 4-space

2000

We consider asymptotic line fields on generic surfaces in 4-space and show that they are globally defined on locally convex surfaces, and their singularities are the inflection points of the surface. As a consequence of the generalized Poincare-Hopf formula, we obtain some relations between the number of inflection points in a generic surface and its Euler number. In particular, it follows that any 2-sphere, generically embedded as a locally convex surface in 4-space, has at least 4 inflection points.

ASYMPTOTIC CURVES ON SURFACES IN ℝ5

2008

We study asymptotic curves on generically immersed surfaces in ℝ5. We characterize asymptotic directions via the contact of the surface with flat objects (k-planes, k = 1 - 4), give the equation of the asymptotic curves in terms of the coefficients of the second fundamental form and study their generic local configurations.

Surface area, density and porosity measurements using the magnetic suspension balance

1989

The advantage of gravimetry in the determination of surface area is discussed in comparison with the volumetric method. The magnetic suspension balance is described and new developments are presented. As an example of the application of gravimetric measurements the determination of apparent density and specific surface area before and after oxidation of a Poco graphite are described.

On the number of singularities of a generic surface with boundary in a 3-manifold

1998

Convergent transformations into a normal form in analytic Hamiltonian systems with two degrees of freedom on the zero energy surface near degenerate …

2004

We study an analytic Hamiltonian system with two degrees of freedom, having the origin as an elliptic singularity. We assume that the full Birkhoff normal form exists and is divisible by its quadratic part, being indefinite. We show that under the Bruno condition and under the restriction to the zero energy surface, a real analytic transformation into a normal form exists. Such a normal form coincides with the restriction of the Birkhoff normal form to the zero energy surface up to an order as large as we want.

Scanning from heating: 3D shape estimation of transparent objects from local surface heating.

2009

Today, with quality becoming increasingly important, each product requires three-dimensional in-line quality control. On the other hand, the 3D reconstruction of transparent objects is a very difficult problem in computer vision due to transparency and specularity of the surface. This paper proposes a new method, called Scanning From Heating (SFH), to determine the surface shape of transparent objects using laser surface heating and thermal imaging. Furthermore, the application to transparent glass is discussed and results on different surface shapes are presented.

On stability of generic subriemannian caustic in the three-space

2000

Abstract The singularities of exponential mappings in subriemannian geometry are interesting objects, that are already non-trivial at the local level, contrarily to their Riemannian analogs. The simplest case is the three-dimensional contact case. Here we show that the corresponding generic caustics have moduli at the origin, and the first module that occurs has a simple geometric interpretation. On the contrary, we prove a stability result of the “big wave front”, that is, of the graph of the multivalued arclength function, reparametrized in a certain way. This object is a three-dimensional surface, which has also the natural structure of a wave front. The projection on the three-dimension…

Tree Singularities: Limits, Series and Stability

2013

A tree singularity is a surface singularity that consists of smooth components, glued along smooth curves in the pattern of a tree. Such singularities naturally occur as degenerations of certain rational surface singularities. To be more precise, they can be considered as limits of certain series of rational surface singularities with reduced fundamental cycle. We introduce a general class of limits, construct series deformations for them and prove a stability theorem stating that under the condition of finite dimensionality of T 2 the base space of a semi-universal deformation for members high in the series coincides up to smooth factor with the “base space of the limit”. The simplest tree…

Balances for Special Applications

2014

Some special applications and the corresponding balances are described in detail: laboratory balances, micro balances vacuum balances, thermo balances, magnetic suspension balances, oscillators, metrological comparators, tensiometer, suspended particles and elementary charge, mass analyser, density determination, particle analysis, magnetic susceptibility, post office and coin scales, body scales, and gravimeter. Vacuum equipment for balances, thermogravimetry, sorptometry, hygrometry, and moisture determination, gravimetric measurement of reaction kinetics, surface tension, ion traps, pyknometry, dust and particle concentration, grain size analysis are described. Gravimetric measurement of…

The roles of teacher–student relationship quality and self-concept of ability in adolescents’ achievement emotions: temperament as a moderator

2020

AbstractThis study examined to what extent teacher–student conflict and closeness, on the one hand, and students’ self-concepts of ability in literacy and mathematics, on the other, are related to students’ achievement emotions (enjoyment, anxiety and boredom) in mathematics and literacy among Finnish early adolescents (N = 854). We also investigated the extent to which these associations are moderated by student temperament (surgency/extraversion, negative affectivity and effortful control). The results showed, after accounting for relevant covariates, that in both school subjects, teacher–student conflict was negatively related to enjoyment and positively to anxiety and boredom, whereas t…