Showing papers by "Leibniz University of Hanover published in 1984"

1,4‐Diazobicyclo[2.2.2]octane‐catalyzed coupling of aldehydes and activated double bonds. Part 3. A short ans practical synthesis of mikanecic acid (4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylic acid)

Abstract: The title dicarboxylic acid 1d has been prepared in 24% overall yield via, 1,4-diazabicyclo[2.2.2]octane (DABCO)-catalyzed coupling of ethanal and tert-butyl propenoate (3) to 4, SN2′-reaction to tert-butyl (Z)-2-romomethyl-2-butenoate (5a), dehydrobrominatin to tert-butyl 2-methylidene-3-butenoate (2c), dimerizatoin to di-tert-butyl 4-vinyl-1-cyclohexene-1,4-dicarboxylate (1c) and acidic ester cleavage. Acidic cleavage of easily obtainable 5a affords (Z)-2-bromomethyl-2-butenoic acid (5a) in 68% yield with respect to ethanal.

Built-in test for CMOS circuits

Abstract: In CMOS technology combinational circuits become sequential in the presence of stuck-open faults. Instead of a single test pattern a sequence of patterns is necessary for each such fault. In this paper two kinds of hardware test generation techniques for built-in testing are described which produce the required sequences. One approach is suitable for sequential CMOS circuits the other for combinational CMOS circuits.

Internal Reactions in Oxide Solid Solutions

Abstract: Oxidation of wustite-type solid solutions (A, B)0 and reduction of sesquioxide solid solutions (A, B)203 can lead to the precipitation of a spinel phase (A, B)304 at an inner reaction front. A representation of the reaction scheme and kinetics for each of the two cases will be given. Observations on the macroscopic morphology of the spinel precipitates and on the structure of the precipitate/matrix interphase boundary are discussed.

1.06 Micron Laser Damage of Thin Film Optical Coatings — a Round Robin Experiment Involving Various Pulse Lengths and Beam Diameters

Abstract: A number of commercially available optical coatings, both antireflective and high reflective, have been tested for their laser-induced damage threshold, involving a total of eight different laboratories. The results obtained and the experimental methods used at these laboratories were discussed among the participants in this round robin at a minisymposium held at Balzers, Liechtenstein, 9–10 Dec. 1982. A final report of the round robin and a summary of the conclusions drawn at that symposium are presented.

Chemical bonding at the polyimide surface

Abstract: Surface spectroscopy techniques (UPS and XPS) have been combined with theoretical calculations to investigate the chemical bonding characteristics of the high‐temperature polymer polyimide Both valence and core electronic structure of the intrinsic (‘‘clean’’) polyimide surface as observed in UPS and XPS are well described by the results of the self‐consistent‐field molecular orbital calculations Even though the polyimide is already fully cured to complete the imidization reaction and form the final molecular structure of the polymer chains, the valence electronic structure of such as‐prepared surfaces changes significantly upon in situ annealing at temperatures above ∼195 °C but well below those which decompose the polymer (≥400 °C) This annealing causes desorption of gas phase H2O and produces the intrinsic polyimide surface The sorption/desorption of H2O is reversible and thermally activated, and it seems to play an important role in the chemical properties of the polyimide surface These changes u

Neutron activation analysis of iodine-129 and iodine-127 in environmental samples

Abstract: An analytical method for129I and127I in various environmental samples is described. The method consists of sample digestion by alkali fusion, iodine separation by solvent extraction, neutron irradiation, radiochemical purification of iodine and gamma-spectrometry. The detection limit of129I and the129I/127I ratio are 1·10−3 pCi and 1·10−9, respectively. The range of the129I/127I ratios obtained in the environmental samples collected from the Tokaimura area in Japan was between 1·10−9 and 7.9·10−6. The highest ratio was observed in pine needles followed by rain water, soil, swamp water and algae.

A Technology Independent Block Extraction Algorithm

Abstract: Functional block extraction is a useful tool for layout verification of integrated circuits. In particular, it facilitates the network comparison problem by transfering it to a higher level of hierarchy. This paper describes a computer program called BLEX (Block Extractor), which is able to extract any given circuit block, e.g., gates, flip-flops, memory cells, differential amplifiers, darlington circuits etc., from a SPICE-like network description. The algorithm is fully technology independent. The size of the blocks is not subject to any restrictions. Descriptions of the functional blocks having the same format as the network description are supplied by the user. The circuit to be examined results usually from a preceding circuit extraction. The extractor and BLEX are part of the layout verification system ALAS (A Layout Analysis System).

2,2,4,4-Tetramethyl-3-methylenebicyclo [3.2.1] oct-6-ene

Abstract: 2,2,4,4-Tetramethyl-3-methylenbicyclo[3.2.1]oct-6-en Die sterisch anspruchsvolle Titelverbindung 1 wurde in einer Eintopfreaktion aus Cyclopentadien und 2,4-Dimethyl-3-[(trimethylsilyl)methyl]-3-penten-2-ol (5) in Gegenwart von Titantetrachlorid/N-Methylanilin hergestellt. 2,2,4,4-Tetramethylbicyclo[3.2.1]oct-6-en-3-on (4) wurde vereinfacht im 15-g-Masstab dargestellt.

Blade Vibration Measurements on Centrifugal Compressors by Means of Telemetry and Holographic Interferometry

Abstract: Mesure des vibrations d'aubes de compresseurs centrifuges par tlelemetrie et interferometrie holographique

A numerical solution of boussinesq type wave equations

Abstract: Numerical models of short waves in shallow water, which are of particular interest for the calculation of the wave climate in harbours and coastal areas, have been presented by Abbott et al. (1978) and by Hauguel (1980). These models are based on the solution of the Boussinesq or Serre type equations. A recent discussion of the range of application for the equations has been presented by McCowan (1982). Nevertheless, there is some uncertainty as to which terms in the differential equations are of importance, and how they are to be approximated. Therefore, no final judgement can presently be made on the accuracy and credibility of the solutions. Research on such models is still in progress and is of high theoretical and practical interest. Some of the aspects of current research relate to the handling of nonlinear terms, the non-reflecting boundary conditions and the transfer capability of the models for spectral input. This paper will reflect on these points.

High temperature molecular beam source reactor

Abstract: Small low residence time flow tube reactors made of alumina and used as molecular beam sources are described In these reactors, gas mixtures are rapidly heated and brought to reaction The composition of the gas leaving the reactor is analyzed by molecular beam mass spectroscopy For quantitative simulation of the reacting gas flow, the theory of one-dimensional compressible flow with friction, heat transfer, and chemical reaction is brought into a form suitable for practical computation The system has been applied to study the thermal decompositions of O3 and N2O The experimental results on both reactions can be well modeled by homogeneous reaction mechanisms with accepted rate constants Heterogeneous reaction steps are shown to be unimportant

Trade unions, corporatism, and inflation

Abstract: This paper examines the argument that the exchange of powers and responsibilities between government and producer group interests (and, in particular, trade unions) under a bargained form of corporatism confers industrial relations benefits in the form of reduced strikes and economic benefits via lessened inflationary pressures Focusing largely on the inflation question, an alternative argument is entered to the effect that corporatist experimentation threatens directly to exacerbate the problem in part correctly diagnosed by certain corporatist analysts in their discussion of the fundamental determinants of inflation Empirical evidence with a bearing on these issues is evaluated

Slope morphology and slope‐forming processes in South Victoria Land, Antarctica

Abstract: Slope‐forming processes in South Victoria Land occur under the most severe climatic conditions. Very low temperatures are combined with extreme aridity which rarely permits surface runoff. In contrast to the situation in arctic regions, slope erosion and solifluction contribute little to the slope morphology. Varying locations within the area and varying bedrock types produce only minimal differences in slope form. The dominant similarities in slope form and talus cover are a product of slope angle. Solifluction lobes are rare, but one example on Nussbaum Riegel in Taylor Valley was investigated. Surface runoff occurs only when there is glacial meltwater during the brief summer, or where there is snowmelt near the coast. Despite the extreme aridity and a very shallow active layer mass wasting does occur on the slopes, as demonstrated by a series of examples. Measurements of the orientation of rock fragments on slope surfaces produced remarkably similar results to comparable investigations in soli...

Our Attitude to Fertilization and Conception

Abstract: This article reexamines attitudes toward fertilization and conception and identifies some of the deeper aspects involved in the creation of a human being. Reproduction is a closed feedback control system with calculable values in which the reference input is determined by an existent or nonexistent desire for a child. The desire for a child is often obsessive arising from a Herculean mania or Messianic fantasy. In such cases the child is made to be the mere object of personal desires. In contrast there are 4 aspects of fertilization and conception that belong to a deeper level of understanding: the feeling of being moved the experience of necessity the anticipatory feeling of certainty and the creation of a 3rd being. This process is quite different from the purposive approach of producing common among neurotics. The Herculean attitude claims the right to form things according to ones own arbitrary decisions or irrational motives; the attitude of letting the child come implies a readiness to accept ones fate with respect to fertility. The attitude of active preparedness attentive silence and of dedicating oneself to something without giving oneself up comprises a desirable middle ground between the 2 extremes of energetic activity and apathetic passivity. As transformers of creation physicians are urged to recognize aspects of fertility and conception that belong to a deeper level of understanding and to move toward an attitude of letting a child come.

Geometrically Nonlinear Theory and Incremental Analysis of Thin Shells

Abstract: Within the last years, a wide variety of complicated geometrically and physically nonlinear shell problems was approximately solved using mainly the Finite Element Method (FEM). Complex engineering structures need large systems of nonlinear equations for incremental load paths. Own investigations, using the SHEBA-element with 63 DOF’s /4/, /8/, have shown that the limit capacity even of large and fast scalar computers (in our case a Cyber 76/73 configuration) may be exceeded in the case of critical and postcritical calculations.

Did Lake Chad exist around 18,000 yr BP?

Abstract: The surface area of the closed Lake Chad is regarded as a product of the climatic parameters in the Chad Basin. With the aid of a simple analytical model using the energy and the water balance the sensitivity of the water volume of the lake with respect to meteorological and hydrological parameters was investigated. A data set is derived describing the climatic conditions in the Chad Basin during the period of the maximum of the northhemispheric glaciation at about 18,000 yr BP. In particular a reduced hydrological input into the lake was assumed as well as higher insolation and wind speed while the air temperature and the atmospheric moisture content were reduced. The resulting surface area of Lake Chad is then diminished by 80% and calculated to be less than 4000 km2.

Notizen. The Synthesis of Iodoglyoxalic Esters. Cleavage of Tetrahydrofuran and 1,2-Dimethoxyethane

Abstract: Die Synthese von Iodglyoxylsaureestern. Spaltung von Tetrahydrofuran und 1,2-Dimethoxyethan Eine Serie von Iodglyoxylaten 2a – i wird aus Chlorglyoxylaten 1a – i und Natriumiodid in Acetonitril dargestellt und durch Tieftemperaturextraktion mit Pentan isoliert. Iodglyoxylsaureester eignen sich zur acylierenden Spaltung von Ethern, z. B. Tetrahydrofuran und 1,2-Dimethoxyethan.

On the euclidean distance between biased estimators

Abstract: The purpose of this paper is to extend the results achieved by Hsuan (1981) to a wide class of biased estimators. It is shown that in the case of multicollinearity ridge and Iteration estimator can be made very close to the principal component estimator whereas the shrunken estimator does not have this property.

Atmospheric physics and Earth observations: mapping from space: the metric camera experiment.

Abstract: The Spacelab metric camera experiment acquired stereoscopic high-resolution black-and-white and color infrared photographs of various regions of the world. In total, an area of about 11 million square kilometers was covered. Because of the delay in launching the shuttle until 28 November, illumination conditions were frequently poor over many candidate targets. However, unique high-quality images with a ground resolution of about 20 meters were obtained by increasing camera exposure time. Initial image analysis has shown that these images may be used for earth mapping at the scale 1:100,000.

The Influence of Different Geometries for a Vaned Diffuser on the Pressure Distribution in a Centrifugal Compressor

Abstract: In this paper the transonic flow field in a vaned diffuser of a contrifugal compressor has been studied Different geometries of the diffuser blades have been considered Particularly with respect to the pressure field it is important to understand their influence on the development of the shock waves For this problem a centrifugal compressor with high pressure ratio per stage has been examined It is assumed that the impeller speed is so large that the flow may become transonic at the impeller exit To calculate flows with shocks a time-marching method is used for solving the two-dimensional Euler equations in a conservative form A MacCormack’s second order difference scheme is applied There are two important points which have been studied in this paper Firstly the geometry of the blades as far as the thickness distribution is concerned is kept unchanged and only the stagger angle has been altered The performance maps of these diffusers and their effect on the whole machine will be discussed Secondly the results which have been obtained by using vanes with different thickness distributions will be presented Mean values of the quantities used for the performance map will be shown Wall pressure distributions as well as fields of isobars and of constant Mach numbers will be demonstrated to provide a better understanding of the pressure recovery in centrifugal compressor diffusersCopyright © 1984 by ASME