478 research outputs found
Order bound for the realization of a combination of positive filters
In a problem on the realization of digital ÂŻlters, initiated by Gersho and Gopinath [8], we extend and
complete a remarkable result of Benvenuti, Farina and Anderson [4] on decomposing the transfer function
t(z) of an arbitrary linear, asymptotically stable, discrete, time-invariant SISO system as a diÂźerence
t(z) = t1(z) ÂĄ t2(z) of two positive, asymptotically stable linear systems. We give an easy-to-compute
algorithm to handle the general problem, in particular, also the case of transfer functions t(z) with multiple
poles, which was left open in [4]. One of the appearing positive, asymptotically stable systems is always
1-dimensional, while the other has dimension depending on the order and, in the case of nonreal poles,
also on the location of the poles of t(z). The appearing dimension is seen to be minimal in some cases
and it can always be calculated before carrying out the realization
Positive decomposition of transfer functions with multiple poles
We present new results on decomposing the transfer function t(z) of a linear, asymptotically stable, discrete-time SISO system as a difference t(z) = t(1)(z) - t(2)(z) of two positive linear systems. We extend the results of [4] to a class of transfer functions t(z) with multiple poles. One of the appearing positive systems is always 1-dimensional, while the other has dimension corresponding to the location and order of the poles of t(z). Recently, in [11], a universal approach was found, providing a decomposition for any asymptotically stable t(z). Our approach here gives lower dimensions than [11] in certain cases but, unfortunately, at present it can only be applied to a relatively small class of transfer functions, and it does not yield a general algorithm
O zakrivljenostima na trokutnim mreĆŸama
A face-based curvature estimation on triangle meshes is presented in
this paper. A flexible disk is laid on the mesh around a given
triangle. Such a bent disk is used as a geodesic neighborhood of the
face for approximating normal and principal curvatures. The radius
of the disk is free input data in the algorithm. Its influence on
the curvature values and the stability of estimated principal
directions are investigated in the examples.U Älanku je prikazana procjena zakrivljenosti na trokutnim mreĆŸama, bazirana na stranicama. Gipki disk poloĆŸen je na
mreĆŸu oko danog trokuta. Takav prilagodljiv disk koristi se
kao geodetska okolina stranice za aproksimaciju normalnih i
glavnih zakrivljenosti. Polumjer diska je nezavisni ulazni
podatak u algoritmu. U primjerima se istraĆŸuje njegov utjecaj na vrijednosti zakrivljenosti i na stabilnost procijenjenih glavnih
smjerova
PARABOLIC BLENDING SURFACES ALONG POLYHEDRON EDGES
In this paper parabolic blending surfaces are defined along a chain of polyhedron edges.
The profile curve of each sweep surface generated for a given edge is a conic section, and
every point of it moves on a conic section around a vertex. According to this, the patches
at the corners are given in rational biquadratic form and they join to the cylindrical
surfaces replacing the edges with 1st order continuity
Filling triangular holes by convex combination of surfaces
A surface generation method is presented based on convex
combination of surfaces with rational weight functions.
The three constituents and the resulting surface are defined
over the same triangular domain. The constructed surface
matches each component along one of its boundary curves
with C0 or C1 continuity depending on the weight
functions in the combination. The method can be applied
in surface modelling for filling triangular holes
FLEXIBLE METHODS OF SURFACE DESIGN WITH FASTSURF
This paper illustrates the powerful design methods of FastSURF, the surface modelling
system of CADKEY. It contains several surface definitions and offers a number of highly
developed methods of constructions and manipulations on surfaces. Solutions for fitting
and trimming problems arising at the construction of composed surfaces are shown on
three practical models
THE RIGHT PLACE OF CAD-COURSES IN ENGINEERING EDUCATION
An educational conception of teaching CAD for beginners is presented based upon the geometric backgrounds of CAD. Teaching of geometric modelling is proposed as an extension
of the fundamental geometry courses
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