Showing papers by "University of Potsdam published in 1994"

Multi-level logic optimization by implication analysis

Abstract: This paper proposes a new approach to multi-level logic optimization based on ATPG (Automatic Test Pattern Generation). Previous ATPG-based methods for logic minimization suffered from the limitation that they were quite restricted in the set of possible circuit transformations. We show that the ATPG-based method presented here allows (in principle) the transformation of a given combinational network C into an arbitrary, structurally different but functionally equivalent combinational network C'. Furthermore, powerful heuristics are presented in order to decide what network manipulations are promising for minimizing the circuit. By identifying indirect implications between signals in the circuit, transformations can be derived which are “good” candidates for the minimization of the circuit. In particular, it is shown that Recursive Learning can derive “good” Boolean divisors justifying the effort to attempt a Boolean division. For 9 out of 10 ISCAS-85 benchmark circuits our tool HANNIBAL obtains smaller circuits than the well-known synthesis system SIS.

Characterization of the new luminescence pressure sensor SrFCl:Sm2+

Abstract: As a new pressure sensor the 5D → 7FO luminescence line of SrFCI:Sm2 + is characterized. The pressure dependence of the line position and the line width are determined within the pressure range of 20 GPa. The relationship between pressure and line position is given by with λ = 690.3 nm, A = 0.904(4) GPa/nm, B = −11.6(7) (p 10 GPa). The temperature effect on the line position and the line width is studied at 20 K, 100 K and from room temperature up to 650 K. Using a simple electron-phonon interaction model the average Debye temperature and the coupling coefficients are evaluated to be Op, = 527(79)K, α = 22(3)cm−1, α = 97(15)cm−1 and β = 2.4(4)cm−1.

Stability and Hamiltonian formulation of higher derivative theories.

Abstract: We analyze the presumptions which lead to instabilities in theories of order higher than second. That type of fourth order gravity which leads to an inflationary (quasi de Sitter) period of cosmic evolution by inclusion of one curvature squared term (i.e. the Starobinsky model) is used as an example. The corresponding Hamiltonian formulation (which is necessary for deducing the Wheeler de Witt equation) is found both in the Ostrogradski approach and in another form. As an example, a closed form solution of the Wheeler de Witt equation for a spatially flat Friedmann model and L=R\sp 2 is found. The method proposed by Simon to bring fourth order gravity to second order can be (if suitably generalized) applied to bring sixth order gravity to second order. In the Erratum we show that a spatially flat Friedmann model need not be geodesically complete even if the scale factor a(t) is positive and smooth for all real values of the synchronized time t.

Multidimensional Classical and Quantum Wormholes in Models with Cosmological Constant

Abstract: A multidimensional cosmological model with space-time consisting of $n (n \ge 2)$ Einstein spaces $M_{i}$ is investigated in the presence of a cosmological constant $\Lambda$ and a homogeneous minimally coupled scalar field $\varphi(t)$ as a matter source. Classical and quantum wormhole solutions are obtained for $\Lambda < 0$ and all $M_{i}$ being Ricci-flat. Classical wormhole solutions are also found for $\Lambda < 0$ and only one of the $M_{i}$ being Ricci-flat for the case of spontaneous compactification of the internal dimensions with fine tuning of parameters.

Bioelectrocatalysis by Immobilized Peroxidase: The Reaction Mechanism and the Possibility of Electroanalytical Detection of Both Inhibitors and Activators of Enzyme

Abstract: Electrocatalytic reduction of hydrogen peroxide by peroxidase immobilized throughits adsorption at carbon black was studied by using the rotating disk electrode technique. The reaction mechanism was proposed on the basis of experimental data concerning the influence of various parameters on the reaction rate: H2O2 concentration, the electrode rotation speed, solution pH, inhibitors and activators. The mechanism was found to be similar to that of peroxidase catalysis in the bulk of the solution, the electrode acting as aromatic reducer substrate. The results obtained on inhibition and activation of H2O2 electroreduction allows us to give recommendation on the electroanalytical detection of CN−, F− ions and bensotriasol.

The renormalized entropy—an appropriate complexity measure?

Abstract: We have studied the renormalized entropy ΔS in the framework of complexity measures. In opposite to other complexity measures, this ΔS is a relative measure, i.e. it is defined relative to a fixed basic state. To investigate its specific capabilities, ΔS has been applied to different dynamical regimes of the logistic map. We have found that the renormalized entropy clearly indicates all transitions: from periodic to chaotic behaviour as well as between different types of chaos, such as band-merging, intermittency or inner crises. ΔS also distinctly describes how additive noise changes the dynamics. Due to these outstanding properties we recommend ΔS for various fields of application.

Word Order Variation, Verb Movement and Economy Principles

Abstract: . In Chomsky's Minimalist framework, word order variation reflects different movement options arising from interaction between parametrized morphological properties of functional items and invariant economy principles. In the simplest case, languages vary in whether a given movement (e. g. V-to-I-raising) feeds PF (French) or not (English). We consider more complex cases involving language-internal word order differences due to construction-specific movement-Germanic Verb-Second, Last Resort Verb fronting in Croatian-showing how they can be explained using the concept of Early Altruism latent in Chomsky's model. We further propose that (i) not only morphological, but also purely phonological properties of lexical items can trigger movement (clitics in Croatian); (ii) both finite and non-finite verbs raise to C in LF; (iii) English do-support is not a Last Resortoperation: instead English ‘simple’ tenses are basically periphrastic, composed of a main verb and a-sometimes abstract-auxiliary.

Novel versatile X-ray reflectometer for angle and energy dispersive characterization of liquid and solid surfaces and interfaces

Abstract: The design and development of a highly flexible reflectometer which allows characterization of surfaces and interfaces of solids and liquids at grazing angles of incidence and exit is described. The reflectometer is capable of operating either in the angle dispersive or energy dispersive mode. In the angle dispersive mode the high resolution capability of the energy dispersive Ge detector is exploited to avoid the use of a monochromator crystal and also to keep the electronic noise extremely low: These factors allow the reflectivity to be measured over a dynamic range of up to 108. X-ray wavelengths are exchanged without any new alignment of the set-up. In the case of layered structures, the resolution of the instrument limits the determination of characteristic lengths to an upper value of 3000 ± 1 A . The angle dispersive mode allows measurements of the reflectivity of surfaces on an absolute scale, while the energy dispersive mode allows qualitative investigations of the time dependent structural changes close to the sample surface. Several examples to demonstrate the performance of the instrument in the two modes are presented: The presence of a thin adsorbed water layer on the surface of a polished, hydrophilic (100) Si wafer and the formation of a monolayer of surfactant lipid molecules at the air/water interface have been demonstrated using the angle dispersive mode. The time resolved measurement of the structural transition of Pb stearate multilayers on Si substrate is reported as an example for the energy dispersive mode.

Operations on cognitive structures — their modeling on the basis of graph theory

Abstract: It is a central problem in cognitive psychology to identify basic components in processes of formation and transformation of internal representations. Operations on internal representations are essential in different fields of cognitive psychology, e. g. in text comprehension and text processing, problem solving, cognitive development, diagnostics, and differential psychology. Thus Kintsch and van Dijk (1978) and van Dijk and Kintsch (1983) identified cognitive operations for the generation of knowledge representations that are typical for processes in text comprehension and text processing, such as operations for generating hierarchies of propositions and for the formation of macro propositions. Parts of the approach of Kintsch and van Dijk could be specified by experimental results of Beyer (1986). Also the analyses of Schnotz, Ballstaedt, and Mandl (1981), Garrod and Sanford (1981), and Ehrlich (1982) are directed to the identification of general cognitive principles in this field. Schnotz (1988) investigated text comprehension as formation of mental models (Johnson-Laird, 1983). The papers of Rickheit (1991) and Strohner (1991) are based on the idea of mental model formation too. Thereby the question for the basic structure of mental models and for operations for its formation as well as the problem of an adequate formalization are of great importance.

Pseudo-differential operators with operator-valued symbols in the Mellin-edge-approach

Abstract: The pseudo-differential Mellin-edge-approach is a tool for studying differential and pseudo-differential operators on manifolds with corners. The Mellin transform, acting on the corner axis ℝ+, is a substitute for the Fourier transform along edge variables in the calculus of wedge pseudo-differential operators. The basic elements of that theory (cf. Schulze [6,8]) are extended to edges like ℝ+ ∋ t with a control of symbols and smoothing operators near the vertext=0. The authors study the weighted Mellin wedge Sobolev spaces, the operator-valued Mellin convention translating Fourier symbols into Mellin ones under preserved smoothness up tot=0, and develop an operator calculus with its characterization on the level of symbols. Throughout the theory, there are involved one-parameter groups of isomorphisms acting on the Banach spaces that are the abstract analogues of the weighted cone Sobolev spaces.

Structural properties of high-quality sputtered Fe films on Al2O3(1120) and MgO(001) substrates

Abstract: High-quality thin Fe films were deposited on MgO(001) and Al2O3(1120) substrates in the thickness range from 7 to 50 nm. The structural properties have been studied by out-of-plane and in-plane X-ray scattering experiments. From the out-of-plane measurements the electron density profile was determined together with interface and surface roughness parameters. Fe on Al2O3 grows along the [110]-direction with a structural coherence length comprising about the total film thick ness and a very small mosaicity. From in-plane scattering experiments a three-domain structure was observed. On MgO(001) substrates Fe grows in the [001]-direction, with the Fe [100]-axis parallel to the MgO [110]-axis. On both substrates, the Fe films exhibit a very small surface and interface roughness, indicative for a high quality of the sputtered samples.

Study of the crosslinking process in fluorinated poly(imide-amide)s containing pendant cyano groups

Abstract: Fluorinated poly(imide-amide)s containing pendant cyano groups have been synthesized by solution polycondensation of aromatic diamines which contain cyano groups with diacid chlorides which have both hexafluoroisopropylidene and imnide groups. Thermal crosslinking of these polymers has been attempted in NMP, or by heating the polymer films up to 370-400 'C. The solubility, thermal stability, glass transition temperature and dielectric constant of both linear and crosslinked polymers have been studied.

The influence of specular interface reflection on grazing incidence X-ray diffraction and diffuse scattering from superlattices

Abstract: Superlattices (SL) with a large difference in the refractive index between the alternating layers give rise to specular reflection from the intrinsic interfaces of the SL which proves very efficient for small incident or exit angles near the critical angle of total external reflection. This influences the intensity of grazing incidence X-ray diffraction (GID) and non-specular X-ray scattering (NSXR). Additional peaks were found besides the common features. They are explained by waves scattered in transmission geometries and measured above the sample surface due to subsequent specular interface reflection. The experimental findings are interpreted by Umweganregung in terms of the distorted wave Born approximation (DWBA).

Absolute Proper Motions of the DWARF Spheroidal Galaxies in Draco and Ursa Minor

Abstract: Palomar and Tautenburg Schmidt plates with a base line of about 35 years have been measured with the Automated Photographic Measuring (APM) system in Cambridge (UK) in order to obtain the proper motions of the Galactic dwarf spheroidal satellites (dSph) in Draco and Ursa Minor with respect to a well defined extragalactic reference frame. The investigations were encouraged by the accuracy level achieved for the mean absolute proper motions of galactic globular clusters (0.05 arcsec/century from 25 years base line Tautenburg plate pairs) which is comparable to the expected proper motion of the Draco and Ursa Minor dSph assuming tangential motions of about 100 km/s. Different methods for the removal of systematic errors in the absolute proper motion introduced by the measuring and reduction process are discussed. The more accurate relative proper motions of individual stars in both dSphs obtained by Stetson (1980) and by Cudworth, Olszewski & Schommer (1986) provide an external comparison and are also used to obtain the mean absolute proper motion of the dSphs.

Synthesis and properties of fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups

Abstract: A series of fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared and investigated to determine their dielectric constants as a function of relative humidity and thermal characteristics. The fluorinated polymides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared by reaction of bis(4-aminophenoxy) benzonitriles with a fluorinated dianhydride and with a fluorinated di(acid chloride) containing preformed imide rings. The properties of the fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were compared with those of fluorinated polyimides and fluorinated poly(imide amide)s prepared from 1,3-bis(4-aminophenoxy)benzene. The introduction of the pendent cyano groups caused an increase in the dielectric constant and an increase in the glass transition temperature of the polymers compared with the polymers prepared without pendent cyano groups.