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61.
62.
Jürgen Schönbeçk 《NTM》2004,12(2):80-99
Thomas Fincke (January 6th, 1561–April 24th, 1656), born in Flensburg (Germany), was one of the very most important and significant scientists in Denmark during the
seventeenth century, a mathematician and astrologer and physician in the beginning of modern science, a representative of
humanism and an influentual academic organizer. He studied in Strasbourg (since 1577) and Padua (since 1583) and received
his M.D. in Basel (1587), he practised as a physician throughout his life (since 1587 or 1590) and became a professor at Copenhagen
(1591). But he was best known because of his Geometriae rotundi libri XIIII (1583), a famous book on plane and spherical trigonometry, based not on Euclid but on Petrus Ramus. In this influentual work,
in which Fincke introduced the terms tangent and secant and probable first noticed the Law of Tangents and the so-called Newton-Oppel-Mauduit-Simpson-Mollweide-Gauss-formula,
he showed himself to be „abreast of the mathematics of his time“.
相似文献
63.
Sorin Manolache Petru Eles Zebo Peng 《International journal of parallel programming》2007,35(2):125-156
As feature sizes shrink, transient failures of on-chip network links become a critical problem. At the same time, many applications
require guarantees on both message arrival probability and response time. We address the problem of transient link failures
by means of temporally and spatially redundant transmission of messages, such that designer-imposed message arrival probabilities
are guaranteed. Response time minimisation is achieved by a heuristic that statically assigns multiple copies of each message
to network links, intelligently combining temporal and spatial redundancy. Concerns regarding energy consumption are addressed
in two ways. First, we reduce the total amount of transmitted messages, and, second, we minimise the application response
time such that the resulted time slack can be exploited for energy savings through voltage reduction. The advantages of the
proposed approach are guaranteed message arrival probability and guaranteed worst case application response time. 相似文献
64.
A fully-dense Cu-75 vol pct ZrW2O8 metal matrix composite was fabricated by hot isostatic pressing of Cu-coated ZrW2O8 particles. A small amount of the high-pressure γ-ZrW2O8 phase was created during the cooldown and depressurization following densification; near complete transformation to γ-ZrW2O8 was achieved by subsequent cold isostatic pressing. The thermal expansion behavior of the composite between 25°C and 325°C
was altered by the cold isostatic pressing treatment, and also depended on the length of time that had passed between thermal
cycles. The measured thermal expansion coefficients within specific temperature ranges varied from −6·10−6 K−1 to far above the thermal expansion coefficient of the copper matrix. The complex temperature-dependent expansion/contraction
behavior could be justified by considering the evolution of phase transformations taking place in the ZrW2O8 phase, which were observed by in-situ synchrotron X-ray diffraction measurements. 相似文献
65.
Nicolas Clauvelin Basile Audoly Sébastien Neukirch 《Scientific Modeling and Simulation》2007,14(1):95-101
The DNA molecule is modeled as an elastic rod with bending and twisting rigidities, subjected to external tension and twist applied at one end, the other end being clamped. We study the plectonemic equilibrium of such a rod, taking into account the impenetrability constraint. Numerical solutions of this boundary value problem have previously shown that purely elastic models can reproduce the supercoiling response of the DNA molecule. Using a variational approach, we derive analytical formulae for the elastic response of the filament, and extend former numerical results. 相似文献
66.
67.
68.
We show new upper bounds for problems in the W-hierarchy of fixed-parameter complexity. A crucial ingredient of our proofs
is an extension to the W-RAM model, which permits more-powerful operations but remains equivalent to the original. We use
the extended model to give new upper bounds for Subsetsum, Maximum Irredundant Set, and various problems concerning intersection
of finite-state machines. 相似文献
69.
Daniel Meister 《Theory of Computing Systems》2007,41(2):257-289
A finite recurrent system over sets of natural numbers of dimension n is a pair composed of n n-ary functions over sets of
natural numbers and an n-tuple of singleton sets of natural numbers. Every function is applied to the entries of the tuple
and computes a set of natural numbers, that may also be empty. The results are composed into another tuple, and the process
is started anew. Thus, a finite recurrent system defines an infinite sequence of n-tuples containing sets of natural numbers.
The last entry of a generated n-tuple is called the output of a step, and the union of the output sets of all steps is the
set defined by the finite recurrent system. Membership problems ask whether a given number is in a specified output set or
in some output set. We study membership problems for special finite recurrent systems, whose functions are built from the
set operations union, intersection and complementation and the arithmetical operations addition and multiplication. Sum and
product of two sets of natural numbers are defined elementwise. We restrict the set of operations from which functions are
built and determine the impact on the complexity of the membership problems. We focus on PSPACE-decidable membership problems
and show completeness results for the complexity classes NL, NP and PSPACE. 相似文献
70.
Dynamic complexity investigates the required effort to maintain knowledge about a property of a structure under changing operations.
This article introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the
basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFL-complete problem D2LREACH(acyclic) can be maintained with first-order updates. 相似文献