128,886 research outputs found
A concept for magazine Bimat processor
Concept utilizes existing film magazines to process photographic film as the film is exposed. A standard magazine can be converted to a Bimat processor by adding three stainless steel rollers. All chemicals required for processing and fixing the negative are contained in the Bimat film
On varieties of almost minimal degree I: Secant loci of rational normal scrolls
To complete the classification theory and the structure theory of varieties
of almost minimal degree, that is of non-degenerate irreducible projective
varieties whose degree exceeds the codimension by precisely 2, a natural
approach is to investigate simple projections of varieties of minimal degree.
Let be a variety of minimal degree and
of codimension at least 2, and consider where . By
\cite{B-Sche}, it turns out that the cohomological and local properties of
are governed by the secant locus of with
respect to .
Along these lines, the present paper is devoted to give a geometric
description of the secant stratification of , that is of the
decomposition of via the types of secant loci. We show
that there are exactly six possibilities for the secant locus , and we precisely describe each stratum of the secant stratification of
, each of which turns out to be a quasi-projective variety.
As an application, we obtain the classification of all non-normal Del Pezzo
varieties by providing a complete list of pairs where is a variety of minimal degree, is a closed
point in and is a Del Pezzo variety.Comment: 20 page
Liapunov functions from auxiliary exact difference equations for nonlinear difference equation stability analysis
Liapunov functions from auxiliary exact difference equations for nonlinear difference equation stability analysi
A New Halo Finding Method for N-Body Simulations
We have developed a new halo finding method, Physically Self-Bound (PSB)
group finding algorithm, which can efficiently identify halos located even at
crowded regions. This method combines two physical criteria such as the tidal
radius of a halo and the total energy of each particle to find member
particles. Two hierarchical meshes are used to increase the speed and the power
of halo identification in the parallel computing environments. First, a coarse
mesh with cell size equal to the mean particle separation is
used to obtain the density field over the whole simulation box. Mesh cells
having density contrast higher than a local cutoff threshold
are extracted and linked together for those adjacent to each other. This
produces local-cell groups. Second, a finer mesh is used to obtain density
field within each local-cell group and to identify halos. If a density shell
contains only one density peak, its particles are assigned to the density peak.
But in the case of a density shell surrounding at least two density peaks, we
use both the tidal radii of halo candidates enclosed by the shell and the total
energy criterion to find physically bound particles with respect to each halo.
Similar to DENMAX and HOP, the \hfind method can efficiently identify small
halos embedded in a large halo, while the FoF and the SO do not resolve such
small halos. We apply our new halo finding method to a 1-Giga particle
simulation of the CDM model and compare the resulting mass function
with those of previous studies. The abundance of physically self-bound halos is
larger at the low mass scale and smaller at the high mass scale than proposed
by the Jenkins et al. (2001) who used the FoF and SO methods. (abridged)Comment: 10 pages, 8 figs, submitted to Ap
Germanium:gallium photoconductors for far infrared heterodyne detection
Highly compensated Ge:Ga photoconductors have been fabricated and evaluated for high bandwidth heterodyne detection. Bandwidths up to 60 MHz have been obtained with corresponding current responsivity of 0.01 A/W
Comment on ``Solution of Classical Stochastic One-Dimensional Many-Body Systems''
In a recent Letter, Bares and Mobilia proposed the method to find solutions
of the stochastic evolution operator with a
non-trivial quartic term . They claim, ``Because of the conservation of
probability, an analog of the Wick theorem applies and all multipoint
correlation functions can be computed.'' Using the Wick theorem, they expressed
the density correlation functions as solutions of a closed set of
integro-differential equations.
In this Comment, however, we show that applicability of Wick theorem is
restricted to the case only.Comment: 1 page, revtex style, comment on paper Phys. Rev. Lett. {\bf 83},
5214 (1999
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