Showing papers by "Braunschweig University of Technology published in 1978"

The detectability of local and global displacements in regular rhythmic patterns

Abstract: The aim of this study is to find out by which mechanism human subjects discriminate a regular sequence of beats from an irregular one. Therefore a detection experiment was conducted in which subjects had to detect one of three different types of displacement within a regular rhythmic pattern. The results are against a theory which assumes that in such a task successive intervals are compared. They are more in favor of a theory that postulates an internal time keeper which is synchronized with the presented pattern.

Experimental Beta-Decay Energies of Short-Lived Light Fission Products*

Abstract: The beta-decay energy of 20 nuclides in the mass region 88≦A≦102 has been measured using the on-line mass separator LOHENGRIN. The experimental values obtained are compared with theoretical predictions of different mass formulae.

On the adequacy of the molecular‐orbital picture for describing ionization processes

Abstract: General arguments concerning the adequacy of the molecular-orbital (MO) ionization picture are given. Whereas the MO ionization picture is found to be valid for both outer valence and core electrons, it may completely break down in the inner valence region. The general considerations are supported by many-body calculations on methane, acetylene, hydrogen cyanide, and dinitrogen tetroxide. It is demonstrated that the breakdown of the MO ionization picture is a common phenomenon.

Die Auslegung elastisch-plastisch beanspruchter Querpreßverbände

Abstract: Elastisch-plastisch beanspruchte Querpresverbande werden nach der Theorie des ebenen Spannungszustands behandelt. Es wird die Fliesbedingung nach Tresca verwendet. Im plastischen Bereich wird das Stoffgesetz aus der Fliesbedingung abgeleitet. Es werden einfache Gleichungen fur die Auslegung elastisch-plastisch beanspruchter Querpresverbande aufgestellt. Numerische Ergebnisse werden mitgeteilt und mit den von G. Lundberg berechneten Werten verglichen.

Yielding of plates with hardening and large deformations

Abstract: A mixed finite element technique is used to study the influence of yielding on buckled plates. Orthogonal anisotropic hardening is determined solely by a yield condition, which is introduced into a mixed functional for the elastic plate by Lagrange Multipliers. The Euler equations of the constrained functional include Prager's normality rule. Numerical results are given for rectangular plates of different size calculated for various material properties.

An X-Band Balanced Fin-Line Mixer

Abstract: The fin-line technique has been used in a balanced 9-11-GHz mixer with a 70-MHz intermediate frequency. The mixer without an IF amplifier has an available conversion loss of less than 5 dB with a 3.8-dB minimum and a SSB noise figure of less than 6.9 dB with a 5.3-dB minimum. The mixer is tunable by variable shorts. It is possible to scale the device to millimeter-wave frequencies.

Thin silicon film p-i-n photodiodes with internal reflection

Abstract: A new kind of silicon p-i-n photodiode is presented which combines broad wavelength response at high quantum efficiencies (450 to 900 nm ~85 percent) and extremely fast response time (typically below 100 ps). The diodes use internal light reflection. Theoretical expressions for different types of gratings are presented. The fabrication steps for both the different kinds of gratings and the diode itself are given. Experimental data of the time and wavelength response prove this expected excellent behavior.

Zur Präparation und Charakterisierung hochmolekularer Polyacrylamide

Abstract: In der vorliegenden Arbeit wird eine Losungspolymerisation zur Darstellung von einheitlichen, linearen, ultrahochmolekularen Polyacrylamiden (PAAm) beschrieben, welche frei von Zusatzen sowie frei von Restinitiator sind. Neben der Bestimmung von Zeitumsatzkurven, Molekulargewicht sowie Molekulargewichtsverteilung wurden die erhaltenen Polymeren mittels IR-Spektroskopie, Elementaranalyse sowie thermogravimetrischen Untersuchungen eindeutig charakterisiert. Unter anderem wurde dabei festgestellt, das PAAm trotz intensiver Trocknung (Gefriertrocknung etc.) ca. 2 bis 9% Wasser bindet. Dieser Wassergehalt ist weitgehend unabhangig von der Morphologie der Proben. Zu den bisher unbekannten [η]-M-Beziehungen in Formamid und athylenglykol wurden orientierende Messungen durchgefuhrt, wobei sich in athylenglykol ein Aufweitungsparameter a <0,5 ergab. Die [η]-M-Beziehungen in Wasser, Formamid und Athylenglykol schneiden sich danach in einem Molekulargewichtsbereich von 3 · 105 bis 4 · 105 (g/mol). Die in Wasser ermittelten ηsp/c-c-Funktionen von ultrahochmolekularem PAAm stellen keine Geraden dar. Bei der Auftragung nach der Schulz-Blaschke-Gleichung ergeben sich wieder Geraden, wobei die Konstante KSB = 0,24 losungsmittelunabhangig ist. The present manuscript describes a solution polymerization representing uniform, unbranched, ultrahigh molecular weight polyacrylamides (PAAm) which are free of additives and rest initiator. In addition to the determination by time-conversion-curves, molecular weight and molecular weight distribution of the polymers were characterized definitely by infrared spectroscopy, elemental analyses and thermogravimetry. Among other things it was established that PAAm binds about 2–9% water in spite of intensiv drying. This amount of water is extensively independent of the morphologie of the samples. Orientating measurements of the unknown [η]-M-relationships in formamide and ethylene glycol were made, showing an exponent in ethylene glycol of a <0,5. The [η]-M-relationships of H2O, formamide and ethylene glycol cut each other in a molecular weight range from 3·105 to 4·105 (g/mol). The determined ηsp/c-c-functions from ultrahigh molecular weight PAAm in water are not straight lines. By plotting after the Schulz-Blaschke-equation one gets straight lines, the constant KSB = 0,24 being independent from the solvent.

Zur Frage der Instabilität von Polyacrylamidlösungen

Abstract: Die Losungsinstabilitat(auch Alterung oder Viskositatsabbau genannt) von hochreinen Polyacrylamiden (PAAm) verschiedener Molekulargewichte wurde untersucht. Diese Instabilitat asert sich durch eine Abnahme der Losungsviskositat und des [η] in Abhangigkeit von der Zeit bei gleichzeitigem Flockungsverlust. Die Losungsinstabilitat tritt nur bei Molekulargewichten M > 1,5 Mill. in wasriger Losung auf. PAAm.-Losungen in Formamid und athylenglykol sind stabil. Die Viskositatsabnahme erfolgt in einem Konzentrationsbereich von c = 0,001 bis 5%. Die Einstellung verschiedener pH-Werte im Bereich von pH = 1 bis 12 mittels Puffersubstanzen sowie die Zusatze von Hydrochinon, Chinon, NaNO2 und Na2SO3 fuhren nicht zu einer Losungsstabilitat. Nur pH = 5 zeigte sich eine Stabilisierung der Losung, die jedoch beim Wechsel der Puffersubstanz bei gleichem pH wiederum in eine Instabilitat uberging. Zusatze von Isopropanol fuhren sowohl bei technischen Handelsprodukten als auch bei hochreinen Laborprodukten zu einer Stabilisierung wasriger PAAm-Losungen. Der Mechanismus der Losungsinstabilitat besteht nicht in einem Molekulargewichtsabbau durch Kettenbruch, sondern offenbar in einer anderung der Losungsstruktur der Einzelmolekule unter Beteiligung von Wasserstoff-Brucken. The solution instability (also called ageing or degradation) of high purity polyacrylamides(PAAm) was examined for a number of different molecular weights. This instability set in by a decrease of the solution viscosity and of [η] depending on time with simultaneous loss of flocculation activity. The instability appears only at molecular weights M > 1,5 mill. in aqueous solutions; in formamide and ethyleneglycole PAAm-solutions however are stable. The viscosity loss was observed at a concentration range c = 0,001 to 5%. The standardization of several pH-values at a range from 1 to 12 by means of buffer substances as well as the addition of hydrochinone, chinone, NaNO2 and Na2SO3 do not lead to a stable solution. Only at pH = 5 a stable solution was obtained but by changing the buffer substance at the same pH the solution became instable again. Addition of isopropanol leads to stable aqueous PAAm-solutions from technical products as well as high purity polyacrylamides. The mechanism of the solution instability is not a decrease of the molecular weight due to chain scission but a change of conformation of the solution structure from single molecules based on hydrogen bonds.

Total beta-decay energies of heavy fission products

Abstract: TheQβ-value of144,145Ba,144,145,147La,145,147,148Ce and148Pr has been measured using mass-separated sources produced at the on-line mass separator LOHENGRIN. The experimental values are compared with mass formula predictions.

Monotonie bei den Quadraturverfahren von Gauβ und Newton-Cotes

Abstract: LetQ n be the quadrature rule of Gauss or Newton-Cotes withn abscissas. It is proven here, thatf (2n)?0 impliesQ n G [f]?Q m G [f] (for allm>n) andQ 2n?1 NC [f]?Q 2n NC [f]?Q 2n+1 NC [f]. It follows that the sequenceQ n[f] (n=1, 2, ...) is monotone, if all derivatives off are positive.

ExperimentalQβ-values of several short-lived nuclides with mass number 85≦A≦103

Abstract: TheQβ-values of85, 86Se,90Br,93Kr,103Nb and103Tc were measured using massseparated sources produced at the on-line mass separator LOHENGRIN. The experimental values are compared with mass formula predictions. Taking also into account earlier results, a subshell-closure effect for the neutron numberN=56 and proton numberZ=38 is shown to exist.

Polymer Entrapment of Microbial Cells: Preparation and Reactivity of Catalytic Systems

Abstract: Polymer entrapment of microbial cells has proven to be an alternative to the immobilization of isolated enzymes, especially where more than one enzyme is involved in the reaction pathway. Oxidative degradation of phenol by Candida tropicalis may serve as an example (1,2).

Sequences of neutron and X-ray flashes during a long-lasting current in a plasma focus device

Abstract: The possibility of increasing the neutron yield of a dense plasma focus by several focus events during a single discharge of an energy store is discussed. On a small focus device supplied with a long-lasting current pulse from an inductive energy store, experiments were carried out where several radiation flashes in rapid succession during one discharge could be observed. By the time-of-flight method the generation of fast neutrons was proved.

Model calculations on the magnetization processes in moderate fields of CuMn-like alloys below the freezing temperature

Abstract: A classical model is developed which explains theS-like magnetization curves of CuMn alloys recently found and their close connection with relaxation processes. Its basis is an anisotropy field taken as uniaxial and an expression for the magnetic energy of a single moment in it following Neel [13]. With the resulting energy barriers,E, the observed magnetization curves are explained as transition states between the “zero point magnetization”M 0=M(T→0) and the thermal equilibrium magnetizationM ∞=M(t→∞,T). The frequency distribution ofE, f(E), which can also be calculated, leads to a satisfactory description of theB- andT-dependences of the relaxation experiments.

INFLUENCE OF THE mat1-M ALLELE ON MEIOTIC RECOMBINATION IN THE MATING-TYPE REGION OF SCHIZOSACCHAROMYCES POMBE

Abstract: Angehrn and Gutz (1968) have shown that homozygosity for the mat1-M allele in diploid strains of Schizosaccharomyces pombe increases mitotic recombination between his7 and mat2. In this paper, we report that meiotic recombination frequencies can vary from 3.4 to 16.1 percent between his7 and his2 and that this variation is due to the combination of alleles at the mat1 and mat2 loci.

Thin Silicon Film p-i-n Photodiodes with Internal Reflection

Abstract: A new kind of silicon p-i-n photodiode is presented which combines broad wavelength response at high quantum efficiencies (450 to 900 nm ~85 percent) and extremely fast response time (typically below 100 ps). The diodes use internal light reflection. Theoretical expressions for different types of gratings are presented. The fabrication steps for both the different kinds of gratings and the diode itself are given. Experimental data of the time and wavelength response prove this expected excellent behavior.

Frequency conversion using harmonic mixers with resistive diodes

Abstract: In the paper, mixers are described that consist of M resistive diodes, e.g. Schottky-barrier diodes in a parallel connection. When such mixers are used in frequency convertors, the diodes are pumped by signals having a frequency M times lower than the frequency of conventional local oscillators. A phase shift equal to multiples of 2π/M is necessary between the pump signals. The frequency multiplication, which is usually carried out in the local-oscillator circuit, is done in the mixer. For this reason it is possible to use pump sources that are much simpler than conventional local oscillators. Often the harmonic mixers proposed in the paper are more complicated than the mixers used so far. Sometimes, however, circuits of moderate complexity can be found, so that a simplification of the frequency convertors is possible. This will be shown by mixers that are pumped at the first or second subharmonic, respectively. Theoretical investigations show that the conversion losses of harmonic mixers are slightly higher than those of conventional mixers.

Ökologie, Fazies und Fauna im Turon des südlichen Münsterlandes : Ein Fazieswirkungsschema

Abstract: Anhand von Faunenvergleichen aus vier verschiedenen isochronen Faziesbereichen wird ein Modell erlautert, das sowohl die deskriptive als auch die bildliche Darstellung der okologischen Beeinflusbarkeit der Fauna erleichtert. Als Beispiel wird die Fauna des Soester Grunsandes (oberes Mittelturon, sudliches Munsterland) und seiner aquivalenten Kalke mit Hilfe dieses Fazieswirkungsschemas untersucht. Es werden die Begriffe »negative Fazieswirkung« (= keine Beeinflussung der Fauna) und »positive Fazieswirkung« (= Beein-flussung der Fauna) verwendet. Da es sich bei den okologischen Einflussen um gerichtete Krafte handelt, wird fur die Richtung der positiven Fazieswirkung der mathematische Begriff »Vektor« (= gerichtete Grose) angewendet; »Plusvektor« fur den Fall: Sonderfazies gunstiger als Normalfazies und »Minusvektor« fur den Fall: Sonderfazies ungunstiger als Normalfazies. Mit Hilfe spatangoider Echiniden (Micraster) wird gezeigt, das bei okofaziellen Beeinflussungen auch evolutive und migrative Gesichtspunkte eine Rolle spielen konnen.

Wave Setup and Design Water Level

Abstract: During the winter of 1975-76 measurements were made by the Leichtweiss-Institut of the Technical University of Braunschweig at the west coast of the island of Sylt in the North Sea. The purpose of the field investigations was to determine the wave-induced setup in the surf zone and on the beach, defined as the height difference between the mean water level (MWL) and the still water level (SWL) and the influence of typical offshore parameters on this phenomenon. A new scheme was defined to determine the MWL as the mean value of the water surface variations measured at incremental time intervals over a certain time span. The maximum setup on the beach can reach values up to 30% of the incident significant wave height. The field investigations have shown that the rise of the mean water level due to wave setup is significant and should be taken in account in determining the design water level for coastal structures.