Showing papers by "University of Paderborn published in 1989"

R-Matrices and Higher Poisson Brackets for Integrable Systems

Abstract: The tri-hamiltonian nature of Lax-equations is revealed: starting with an R-matrix on an associative algebra g equipped with a trace form there are g compatible Poisson brackets with linear, quadratic and cubic dependence on the coordinates. The invariant functions (Casimir functions) on g* are in involution relative to these brackets, they yield a hierarchy of integrable tri-hamiltonian Lax-equations. The results can be applied to solvable PDE’s such as the Korteweg-de Vries equation as well as to finite integrable systems such as the Toda lattice. In these cases the Poisson structures considered here turn out to be abstract versions of the first 3 hamiltonian operators of these equations obtained by their well-known recursion operators.

Mastersymmetries and Multi-Hamiltonian Formulations for Some Integrable Lattice Systems

Abstract: On obtient des quantites conservees, une formulation bi-hamiltonienne, une structure recursive et des symetries hereditaires pour un nombre de systemes reticulaires ayant une signification physique. On donne, pour les solutions multisolitons, des variables d'angle. A part le reseau de Toda bien etudie, ces systemes incluent: un reseau de Volterra, un systeme Network concentre, un reseau de Kac-Moerbeke-Langmuir et une classe d'equations de Network. On n'utilise pas la representation de Lax ou toute autre information additionnelle concernant les equations etudiees. Toutes les quantites sont trouvees d'une maniere purement algorithmique en utilisant les symetries maitresses

Trace enrichment and HPLC analysis of polycyclic aromatic hydrocarbons in environmental samples, using solid phase extraction in connection with UV/VIS diode-array and fluorescence detection

Abstract: Both the separation of polycyclic aromatic hydrocarbons (PAH's) on tailor made HPLC phases, and their chromatographic enrichment and quantitative determination are of great interest. Because of the generally low concentrations of PAH's in the environment, and the low limiting values in German legislation for drinking water, methods for selective enrichment and sensitive detection are indispensable. On account of their relatively high amounts in soil, the determination of PAH's is valuable for the assessment of the potential danger to ground water by waste materials. These requirements can be fulfilled by used of solid phase extraction on enrichment columns, and fluorescence or UV/VIS diode array detection.

Digital simulation of nonlinear circuits by wave digital filter principles

Abstract: The known principles of wave digital filters are used to simulate certain nonlinear circuits by digital means. Nonlinear elements-in particular, resistances having a continuous piecewise-linear voltage-current characteristic-are considered. It turns out that a representation of a nonlinear resistance in terms of the wave variables may exist, even if the voltage-current characteristic is neither voltage-controlled nor current-controlled. As an example, Chua's circuit is considered. It is shown that in the wave digital model of this circuit, essentially the same double-scroll attractor can be observed as in the corresponding analog realization. >

On the number of rounds necessary to disseminate information

Abstract: Assume each processor in a network has some piece of information. We study how efficiently information can be spread in a communication network. Specifically, we investigate the number of rounds necessary to spread all the pieces of information to all processors. This problem is known as the "gossip" problem, and initially, the question was to determine the number of telephone calls necessary to achieve complete dissemination. In this paper we study the "telegraph comnmnication node", where in each round, each processor is active only via one of its links and the communication is one-way, i.e. each processor can either transmit or receive, but not both. For an even number of processors, we prove upper and lower bounds on the number of rounds needed for disseminating the information in this telegraph mode. The two bounds are related to Fibonacci numbers and differ by, at most, an additive constant of 1. Our lower bound technique uses elements from matrix theory, specifically matrix norms. These results show, for the first time, that in the two-way mode, information can be distributed faster than in the one-way mode. Similar techniques are applied to obtain upper and lower bounds on the number of rounds needed for gossip in other communication modes. We consider the (pR, qS) communication modes, where during each round each processor can receive information from at most p processors or can send information to at most q processors, but no processor can send and receive during the same round. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission.

A visual language compiler

Abstract: The SIL-ICON compiler is a software system for the specification, interpretation, prototyping, and generation of icon-oriented systems. The system design of the SIL-ICON compiler is presented. The icon system G, the icon dictionary ID, the operator dictionary OD, and the extended task action grammar ETAG are described. An application example to design a text editor using the Heidelberg icon set is also presented in detail. >

Weak and classical solutions of the two-dimensional magnetohydrodynamic equations

Abstract: (u10(x), u20(x)) and B0=B0(x)=(B10(x), B20(x)) denote the given initial data and v denotes the unit outward normal on •Ýƒ¶. The first purpose of this paper is to show the existence and uniqueness of a global weak solution of (*) without restriction on the data. In case B is identically equal to zero, i.e., in the case of the Euler equations, such a problem for global weak and classical solutions was solved by Bardos [1] and Kato [8], respectively. (Kikuchi [9] extended the result of Kato [8] in an exterior domain.) Using the energy method developed by Bardos

Zur Charakterisierung von Eigenschaften der versteiften dreizähnigen Aminophosphanliganden N,N'‐Bis(diphenylphosphino)‐2,6‐diaminopyridin und N,N‐Bis(diphenylphosphino)‐2‐aminopyridin mit Metallen der Chromgruppe

Abstract: Inhaltsubersicht. Edukte von Typ M(CO)6 (M = Cr, Mo,W), N,N'-Bis(diphenylphosphino)-2,6-diaminopyridin (PNP) und Trimethylaminoxid setzen sich bei Raumtemperatur nicht zu dem bekannten Verbindungstyp mer-M(CO)3PNP, sondern zu Verbindungen der beiden Typen M(CO)4(PNP=O) mit zweizahnig koordinierten Liganden PNP=O und M(CO)5(NMe3) um. Die zu Vergleichszwecken untersuchte Oxidation eines koordinierten PNP-Liganden von mer-Mo(CO)3(PNP) in Tetramethylbenzollosung ergibt mit Luftsauerstoff bei 180°C eine Reaktion unter Spaltung der P–N-Bindung zur cubanartigen Verbindung Mo4(μ3-O)4(μ-Ph2PO2)4O4 (Ausbeute 48%). In einem Glaseinschlusrohr reagiert der ambidente N,N-Bis(diphenyIphosphino)-2-nminopyridin-Ligand (NPP) mit den Hexacarbonylen M(CO)6 in Toluollosung bei 140°C zu Verbindungen des Typs M(CO)4(NPP) mit zweizahniger Verknupfung des NPP-Liganden. Hierbei bilden die beiden P-Donoratome am Aminstickstoffatom einen MP2N-Chelatvierring an Stelle des ebenfalls moglichen P, Npy-Chelatfunfrings. Der analoge Chelatvierring entsteht gleichfalls bei einer Ligandensubstitutions-reaktion zwischen Verbindungen des Zweikernkomplextyps MM′(CO)8(μ-PPh2)2 (M = M′ = W; M = Mo, M′ = W) bzw. \V(CO)4(μ-PPh2)2IrH(CO)(PPh3) und NPP. Er bildet sich auserdem bei der Thermolyse von Mo(CO)4(NPP) zu Mo2(CO)6(μ-PPh2)2(NPP). Die Identifizierung erfolgt im Falle der Verbindungen Mo(CO)4(PNP=O), Mo4(μ3-O)4(μ-Ph2PO2)4O4′ Mo2(CO)6(μ-PPh2)2(NPP) und W(CO)4(μ-PPh2)2IrH(CO)(NPP) durch Einkristall-Rontgenstrukturanalysen. Alle isolierten Produkte werden durch spektroskopische Messungen insbesondere 31P-NMR-Daten charakterisiert. Characterization of Properties of the Rigid Tridentate Chelate Ligand N,N′-Bis(diphenylphosphino)-2,6-diaminopyridine and N,N-Bis(diphenylphosphino)-2-aminopyridine with Transition Metals of the Chromium Group Hexacarbonyls M(CO)6 (M = Cr, Mo, W), N,N′-Bis(diphenylphosphino)-2,6-diaminopyridine (PNP) and trimethylamine oxide gave products of two types M(CO)4(PNP=O) having a bidentate ligand PNP=O and M(CO)5(NMe3) instead of the desired mer-M(CO)3PNP. For the purpose of a comparison, aerial oxidation of mer-Mo(CO)3PNP in tetramethyl benzene solution at 180°C was examined which resulted a P–N bond rupture under formation of the cubane-like product Mo4(μ3-O)4(μ-Ph2PO2C4O4){yield 48%). In sealed glass tubes the ambidentate ligand N,N-bis(diphenylphosphino)-2-aminopyridine (NPP) was reacted with the hexacarbonyls M(CO)6 in toluene solution at 140°C to products of the type M(CO)4NPP with NPP as bidentate ligand. Under this reaction conditions the four-membered chelate ring of the type MP2N was formed with the two P donor atoms attached to the amine N atom instead of the possible competitive five-membered chelate ring formation with a P and pyridyl nitrogen. The analogous four-membered chelate ring was formed in ligand substitution reactions between the substance NPP and each of the dinuclear coordination compounds MM′(CO)8(μ-PPh2)2 (M = M′ = W, M = Mo, M′ = W) including W(CO)4(μ-PPh2)2IrH(CO)(PPh3); Mo2(CO)6(μ-PPh2)2(NPP) was obtained via thermolysis of Mo(CO)4(PNP=O). The given structural identification of the compounds Mo(CO)4(PNP=O), Mo4(μ3-O)4(μ-Ph2PO2)4O4, Mo2(CO)6 (μ-PPh2)2(NPP) and W(CO)4(μ-PPh2)2IrH(CO) (NPP) was done by single-crystal X-ray analysis. All seperated products have been characterized by means of spectroscopic measurements especially 31P n.m.r. data.

Abstract LP estimates for the Cauchy problem with applications to the Navier‐Stokes equations in exterior domains

Abstract: We apply an abstract perturbation theorem to derive global in time Lq estimates for the Cauchy problem and Lq − Ls estimates for the nonstationary Stokes equations in exterior domains. This will be applied to obtain various new global in time estimates for weak solutions of the Navier-Stokes equations.

Soliton structure versus singularity analysis: Third-order completely intergrable nonlinear differential equations in 1 + 1-dimensions

Abstract: Backlund transformations between all known completely integrable third-order differential equations in (1 + 1)-dimensions are established and the corresponding transformations formulas for their hereditary operators and Hamiltonian formulations are exhibited. Some of these Backlund transformations are not injective; therefore additional non-commutative symmetry groups are found for some equations. These non-commutative symmetry groups are classified as having a semisimple part isomorphic to the affine algebra A (1) 1 . New completely integrable third-order integro-differential equations, some depending explicitly on x , are given. These new equations give rise to nonin equation. Connections between the singularity equations (from the Painleve analysis) and the nonlinear equations for interacting solitons are established. A common approach to singularity analysis and soliton structure is introduced. The Painleve analysis is modified in such a sense that it carries over directly and without difficulty to the time evolution of singularity manifolds of equations like the sine-Gordon and nonlinear Schrodinger equation. A method to recover the Painleve series from its constant level term is exhibit. The soliton-singularity transform is recognized to be connected to the Mobius group. This gives rise to a Darboux-like result for the spectral properties of the recursion operator. These connections are used in order to explain why poles of soliton equations move like trajectories of interacting solitons. Furthermore it is explicitly computed how solitons of singularity equations behave under the effect of this soliton-singularity transform. This then leads to the result that only for scaling degrees α = -1 and α = -2 the usual Painleve analysis can be carried out. A new invariance principle, connected to kernels of differential operators is discovered. This new invariance, for example, connects the explicit solutions of the Liouville equation with the Miura transform. Simple methods are exhibited which allow to compute out of N -soliton solutions of the KdV (Bargman potentials) explicit solutions of equations like the Harry Dym equation. Certain solutions are plotted.

Two Strategies for Solving the Vertex Cover Problem on a Transputer Network

Abstract: In this article, we present an implementation of a distributed branch and bound algorithm solving the Vertex Cover problem on a network of up to 63 Transputers.

The influence of pressure on the OH valence vibration of zoisite

Abstract: The influence of pressure on the OH-stretching vibration of zoiste has been studied by single crystal high pressure infrared spectroscopy. A band related to the OH-stretching vibration displayed a linear shift from 3170 cm−1 at 1 bar to 2795 cm−1 at 116 kbar. The half-band width increased linearly with respect to pressure from 60 cm−1 at 1 bar to 500 cm−1 at 116 kbar. The strength of the absorption of this band is strongly frequency dependent. The high-energy shift of a band at around 2200 cm−1 on pressure increase indicates that this band is not due to a second OH-stretching vibration as previously suggested by Langer and Lattard (1980).

The helical structure of highly ordered smectic phases

Abstract: Optical studies of smectic phases have been performed in homogeneously oriented samples of chiral 4-(2′-methylbutyl) phenyl-4′-n-octylbiphenyl-4-carboxylate (CE8). The helix structure has been found in smectic phases C, I and J, but not in the smectic G phase. Two chiral phases have been found between SI* and SG phases. Up to now one of them has not been observed. The pitch of the helix has been measured in all of the twisted smectic phases, including the SJ* phase. The existence of the helix in this phase suggests that the correlations between smectic layers are not very strong.

Unification of the properties of the EL2 defect in GaAs.

Abstract: We provide experimental unification of the properties of EL2 in GaAs, linking the measurements of optical absorption, deep-level transient spectroscopy, electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), optically detected electron-nuclear double resonance (ODENDOR). Results show that the EL2 defect has two energy levels, gives rise to the zero-phonon line in the neutral charge state, and gives rise to the EPR quadruplet, MCD, and ODENDOR signals in the singly ionized state. These manifestations disappear when EL2 is transferred to the metastable state. Any discussion of the properties of the EL2 defect must be consistent with these unified characteristics.

Geometry and action-angle variables of multi soliton systems

Abstract: For all completely integrable nonlinear hamiltonian systems which have a localized hereditary recursion operator, a complete action-angle variable representation is given for the multisoliton manifolds. Here multisoliton manifolds are defined as reductions with respect to suitable linear sums of symmetry generators. The embedding of these multisoliton manifolds, into the manifold of all solutions, is described in terms of the construction of its tangent bundle. The basis vectors of the respective tangent spaces are given by local densities. This local geometrical description of the tangent bundle turns out to be independent of the special structure of the particular equation under consideration. The principal tool for finding the necessary geometrical quantities are the canonical commutation relations for the so called mastersymmetries. These relations reflect the hereditary structure. All mastersymmetries turn out to be elements of the tangent space. Although the mastersymmetries, in the case under consideration, principally cannot be hamiltonian, suitable integrating factors are found which make them hamiltonian on the reduced manifold. So, up to suitable linear combinations, the mastersymmetries are shown to correspond to the angle variables. The action-angle-structure found in this way is put into one-to-one correspondence with the spectrum of the recursion operator. The spectrum of this operator is shown to be of multiplicity two and all its eigenvectors are explicitly constructed. Again, this construction is of a canonical nature, i.e., independent of the particular equation under consideration. For vanishing boundary conditions the given action-angle-structure is compared to the asymptotic data (speeds and phases), and the gradients of these global asymptotic data are given in terms of local quantities. It turns out that for all times during the evolution the derivatives of the field function with respect to any particular asymptotic datum yields an eigenvector of the recursion operator. Thus a method is given for reconstructing the spectral resolution of the recursion operator by partial derivatives. This method yields new methods of solution for other equations (for example the singularity equation and the Harry Dym equation). The superposition formula for phase shifts is shown to hold in all generality for the systems under consideration. Several examples are given. An extensive comparison of the present results with the work of others is carried out.

Magnetic field-induced instabilities in cholesteric liquid crystals: Periodic deformations of the Grandjean texture

Abstract: The effect of a magnetic field applied perpendicular to the helical axis of a cholesteric liquid crystal mixture with positive diamagnetic anisotropy has been studied by laser diffraction and microscopy. A rapid decrease of the field below a threshold H s generates first a metastable periodically striated texture. A further decrease of the field below a second threshold H 0 transforms this into a metastable square grid texture. These periodic textures gradually convert into a stable planar texture. The periodic deformation structures can be explained by a simple model based on the hindered relaxation of the partially unwound cholesteric helix under certain boundary constraints.

Scale‐up laws in heated tool butt welding of HDPE and PP

Abstract: In order to achieve high fatigue strengths in heated-tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated-tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small-pipe to large-pipe welds are then based on the values of these nondimensional numbers.

Heart sound analysis using neural and statistical classifiers: a comparison

Abstract: The results of a classical pattern recognition approach to heart sound analysis are compared with those of a trained neural network classifier. Noise not correlated with the specific heart operation is reduced by use of adaptive digital online filtering. The results, indicating the advantages of learning neural classifiers, are regarded as being transferable to other applications. >

Effect of molecular rotational hindrance on the spontaneous polarization in the S*C phase of a ferroelectric liquid crystal

Abstract: The spontaneous polarization, P s, and the tilt angle, θ, have been measured simultaneously in the S*C phase of binary mixtures of two ferroelectric liquid crystals as a function of temperature and concentration. A molecular rotational model was used in order to calculate the temperature dependence of the P s/θ ratio. A two parameter fit of the experimental data was carried out which showed good agreement. The molecular rotational potentials have been determined from the fit parameters and are presented as a function of concentration. It is shown that the chiral part of the potential depends very weakly on the composition in contrast to the non-chiral part which shows a strong negative non-linear deviation with a minimum corresponding to the concentration at which the smectic C* phase width is maximal.

High-performance-liquid chromatographic separation of 1,3,5-trizine herbicides

Abstract: A number of 11 triazine herbicides and 7 of their corresponding metabolites were separated in a single HPLC run. The separation was achieved on a reversed-phase column using gradient elution with acetonitrile/buffer. Detection was by UV absorption at a wave-length of 220 nm.

Process data acquisition in vibration welding of thermoplastics

Abstract: A measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process—such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane—and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.

Production rates of CO2 by suspended and immobilized bacteria degrading 6-amino-2-naphthalenesulphonic acid

Abstract: Production rates of CO2 were calculated on the basis of kinetic data obtained from 6-amino-2-naphthalenesulphonic acid (6A2NS) degradation with a mixed bacterial culture. A linear correlation between product (CO2) formation and growth rate was found for submersed growing cultures as well as for bacteria immobilized on sand particles. For immobilized biomass a distinction was made between active cells and bacterial exopolymers using model calculations.

Structures of the heat-treatment centers NL8 and NL10 in silicon.

Abstract: An electron-spin-resonance investigation on n-type (P-doped) and an electron-nuclear double-resonance (ENDOR) investigation on p-type (B- and Al-doped) Czochralski-grown oxygen-rich Si was performed after annealing at 460 \ifmmode^\circ\else\textdegree\fi{}C and formation of the heat-treatment centers Si-NL8 and Si-NL10. The NL10 defects have different structures influenced by the silicon dopants in contrast to NL8. It is shown that a recent suggestion that NL10 could be an acceptor state of NL8 is not convincing.

Efficient quadrature for a boundary element method to compute three‐dimensional Stokes flow

Abstract: Une methode d'elements frontieres du type collocation basee sur des splines B bilineaires est utilisee pour la resolution numerique du probleme de Stokes-Dirichlet dans un domaine borne