Showing papers by "Braunschweig University of Technology published in 1977"

Magnetic field experiment for Voyagers 1 and 2

Abstract: The magnetic field experiment to be carried on the Voyager 1 and 2 missions consists of dual low field (LFM) and high field magnetometer (HFM) systems. The dual systems provide greater reliability and, in the case of the LFM's, permit the separation of spacecraft magnetic fields from the ambient fields. Additional reliability is achieved through electronics redundancy. The wide dynamic ranges of ± 0.5 G for the LFM's and ± 20 G for the HFM's, low quantization uncertainty of ± 0.002 γ (γ = 10−5 G) in the most sensitive (± 8 γ) LFM range, low sensor RMS noise level of 0.006 γ, and use of data compaction schemes to optimize the experiment information rate all combine to permit the study of a broad spectrum of phenomena during the mission. Objectives include the study of planetary fields at Jupiter, Saturn, and possibly Uranus; satellites of these planets; solar wind and satellite interactions with the planetary fields; and the large-scale structure and microscale characteristics of the interplanetary magnetic, field. The interstellar field may also be measured.

Fundamental mode microbending loss in graded-index and W fibres

Abstract: The microbending loss in single-mode or quasi-single-mode fibres is approximately determined from a calculation of the fundamental mode field in a fibre with constant curvature. The result of the microbending loss essentially depends on the spot size of the fundamental mode, only. The approximations are verified by studying a statistical model and by comparing the approximations with exact calculations in the case of W fibres.

Cubic B-spline curves and surfaces in computer aided geometric design

Abstract: Representations of cubic and bicubic splines are given, combining the advantages of B-splines with the handiness of Bezier technique. The Bezier points of spline curves and surfaces are found by forming convex combinations of nodes. The given algorithms are suited especially for computer aided geometric design.

Inertial normal-force corrections in rotational rheometry

Abstract: When making normal-force measurements in cone-and-plate, parallel plate, or Eccentric Rotating Disc (E. R. D.) geometries, a correction for inertial effects is often imperative. This is especially true when making measurements at high rotation speeds, using large diameter tools, or when the material under test generates little normal-force (e. g. for fluids of low viscosity and elasticity). Theoretical expressions for this correction are quoted herein and are tested for a variety of Newtonian fluids and test geometries. These are found to be accurate to within an experimental error of maximal 4%. Surface tension has no influence. The correction for parallel plate and cone-and-plate is different from that for E.R.D. It is also demonstrated herein that failure to make this correction can lead to apparent first normalstress differences which are greatly in error and even negative for polymer solutions. This is illustrated with an example using aqueous polyacrylamide solutions.

Rheologie pathologischer Gelenkflüssigkeiten

Abstract: Zur Charakterisierung der Losungsstruktur pathologischer Synovialflussigkeiten wurden parallel rheologische Untersuchungen sowohl im Bereich konzentrierter als auch verdunnter Losungen durchgefuhrt. Durch die Berucksichtigung der Scherabhangigkeit der Grenzviskositatszahl [η] und Messung bei niedrigen Schergeschwindigkeiten (D ≅ 2,9 ⋅ 10−3 − 4,6 s−1) errechneten sich hohere Molekulargewichte der Hyaluronsaure (HA) als bisher angegeben. Fur entzundliche Gelenkergusse betragen sie (2,4–12,0) ⋅ 106, fur nicht entzundliche (3,1–11,4) ⋅ 106 und sind damit gegenuber der normalen Synovia mit 16,2 ⋅ 106 erniedrigt. Unterschiedlichek SB-Werte sprechen zusatzlich fur eine starkere Verknauelung der HA-Makromolekule in der pathologischen Synovia. Durch Ermittlung der kritischen Polymerkonzentration der HA sowie der Verhangungszahlenv aus Anlaufmessungen konnten quantitative Aussagen zum makromolekularen Netzwerk getroffen werden. Die normale Synovia entspricht einem sehr engmaschigen und dichten Netz, aber auch in den pathologischen Gelenkflussigkeiten ist die HA nicht im Sinne einer Partikellosung isoliert, sondern bildet ein, wenn auch lockeres Netzwerk mit wesentlich niedrigerer Verhangungszahl. Eine Erniedrigung der Viskositat und Elastizitat isolierter HA weist darauf hin, das molekulare Wechselwirkungen zwischen HA und anderen Makromolekulen in der Synovialflussigkeit fur das rheologische Verhalten von wesentlicher Bedeutung sind. Relaxationszeitmessungen in Ruhe und unter Scherung zeigten eine vermehrte Segmentbeweglichkeit des Netzwerkes der pathologischen Synovia als Folge der HA-Konzentrationsabnahme und/oder Molekulargewichtsverminderung.

Finite length effects in linear induction machines with different iron contours

Abstract: Finite iron and winding lengths are significant factors in determining the performance of linear induction machines. This study provides information on the effect of the iron contour on machine performance, and also aids in the evaluation of other analytical models by pointing out the importance of the proper treatment of finite iron length. The analytical model used here, developed by Mosebach, is based on Fourier series expansions of the electromagnetic quantities and the air-gap length. The magnetic flux density, current density, force density, and efficiency are compared for six iron contours. One case with a graded winding is also considered.

The adsorption of volatile aroma constituents by foods. VIII. Adsorption of volatile carbonyl compounds by amino acids.

Abstract: The adsorption of some volatile aldehydes and ketones by 22 dry amino-acids was studied. The adsorbed amounts decreased approximately in the order: propanal, biacetyl, hexenal, hexanal, acetone, pentan-3-one, nonan-3-one, undecanal and nonan-5-one, but there were great differences in the adsorption capacity of the amino acids. Lys adsorbed best and often irreversible, arg, his, phe, trp, pro, and val (leu, ile) very good. With cys, thiazolidinecarboxylic acids were formed. In most cases of adsorption exceeding 100 mmol/mol, except for the monoketones, strong discoloration, probably of the maillard type, was observed. Propanal and hexanal were to a great extend converted to aldol addition and condensation products. Tyr and hyp adsorbed less than the corresponding amino-acids without hydroxyl groups. This is attributed to stronger crystal-lattice forces.

Electrical performance of finlines of various configurations

Abstract: The characteristics of new microwave integrated circuits called earthed and isolated finlines, namely the cutoff wavelength, the equivalent dielectric constant, attenuation constant, and characteristic impedance based on power-voltage and power-current definitions are calculated The ridged waveguide characteristics are found direct from the results of the earthed finline setting ?r = 1 For some symmetrical configurations the transcendental equations resulting from the calculations can be solved approximately; the results being represented in a closed form approximate to those arising from numerical calculations to a high degree Some of the results are confirmed by measurements

Über die Konstruktion von B-Spline-Kurven

Abstract: Die Konstruktion verbindet die Vorteile der Kurvendarstellung von Bezier mit denen derB-Splines, fur deren Entwicklung nach Bernstein-Polynomen ein einfacher Algorithmus angegeben wird. Damit zerfallt der bekannte Algorithmus von de Boor zur Bestimmung der Splinepunkte in zwei Teile: eine vom Kurvenpunkt unabhangige Bestimmung der Koeffizienten der Entwicklung und eine von der Segmentierung unabhangige Bestimmung der Kurvenpunkte. The construction combines the advantages of Bezier representation with those ofB-splines. A simple algorithm calculates the Bezier polygon from nodes. Hence the wellknown algorithm of the Boor decomposes into two parts: the calculation of the Bźier polygons, independent of the curve points, and the calculation of the curve points, independent of the segmentation.

Superposition of Permeation and Adsorption Effects in Liquid Chromatography

Abstract: A generalized treatment of the superposition of separations based on gel-permeation chromatography (GPC) and liquid-solid chromatography (LSC) is presented Special emphasis is given to the fact that restricted-pore entry behaviour in GPC automatically eliminates part of the surface accessible for adsorption in LSC Therefore the simple additivity rule for KGPC and Kads, applied so far exclusively to “adsorptive GPC” interpretation, cannot be used in general and special care has to be taken if information about adsorptivities is to be deduced from the chromatographic experiment

High-sensitivity dielectric loss measurements by using superconducting microwave resonators in an oscillator loop

Abstract: The method allows easy and highly accurate measurements of microwave resonator parameters. By using superconducting resonators, the loss tangent of polyethylene at 2.2 K and 6.5 GHz was found to be the lowest of any solid so far measured: tan δ = 3.7 × 10-7 ± 7%.

On Keats' Generalization of the Rasch Model.

Abstract: Parameter estimation for Keats generalization of the Rasch model that takes account of guessing behavior is investigated. It is shown that no minimal sufficient statistics for the ability parameters independent of the difficulty parameters exist. Thus Andersen's conditional inference technique for consistent estimation is not applicable to Keats' model. The notion of separability of the parameters is generalized.

The decay of136Te (20.9 s)

Abstract: The beta decay of136Te has been investigated with the on-line mass separator LOHENGRIN from the Institute Laue-Langevin at Grenoble in conjunction with an air-jet collecting system. A level scheme of136I based on coincidence measurements has been established. The measuredQ β value is 5100±150 keV.

Switching in miniaturized planar gunn devices

Abstract: Experimental results are given on miniaturized planar Gunn devices fabricated from epitaxial GaAs. Since it is intended to clarify the conditions for miniaturizing the devices are operated under pulse bias voltage. Typically the devices are 10 μm long and 1 μm thick laving carrier concentration around 1016 cm−3 which concentration range recently found special interest in calculations and experiments. Gunn switching of the travelling domain type is found with a carrier concentration of 6.5 × 1016 cm−3, but not with devices the channel width of which is less than 5 μm. From measurements of the current drop associated with a travelling domain an inactive zone of length of about 4 μm is deduced which is considered as composed of the dead zone, necessary for the thermalization of the electrons, and of an alloyed region, formed by diffusion of contact metals. Bistable switching is established with planar devices without taking recourse to a divided anode structure. Es wird uber experimentelle Ergebnisse berichtet, die an miniaturisierten planaren Gunn-Elementen aus epitaktischem GaAs gewonnen werden. Da die Bedingungen fur die Miniaturisierung geklart werden sollen, werden die Bauelemente nur impulsmasig betrieben. Die Bau-elemente sind 10 μm lang und 1 μm dick mit Ladungstragerkonzentrationen im Bereich um 1016 cm−3, der in letzter Zeit sowohl theoretisch als auch experimentell besonders Interesse fand. Gunn-Effekt mit wandernden Domanen wird bei Ladungstragerkonzentrationen von 6,5 × × 1016 cm−3 gefunden, aber nicht bei Bauelementen, deren aktiver Kanal schmaler als 5μm ist. Aus einer Analyse des Stromimpulses, der mit einer wandernden Domane verbunden ist, wird eine inaktive Zone von etwa 4 μm Lange abgeleitet. Diese Zone setzt sich zusammen aus der „dead zone”, die zur Thermalisierung der Elektronen notwendig ist, und aus einer hochdotierten Zone, die sich durch Diffusion der Kontakt-Metalle bildet. Bistabiles Schalten wirdmit planaren Bauelementen experimentell nachgewiesen, die keine besonderen Anodenstrukturen besitzen.

Added mass of pile group

Abstract: Through laboratory investigation, it is shown that when a pile group is arranged in a cluster, the added mass (or inertial force) increases sharply after the spacing between piles falls below a certain critical value. Two configurations of pile group arrangement—circular and square shapes of approximately the same base diameter—were tested. The experimental results reveal that when the spacing between piles is smaller than two times the pile diameter, or the solidification ratio becomes larger than 0.5, the added mass of the pile group increases drastically. For pile groups with individual pile spacing less than this critical value, the volume enclosed, rather than the volume displaced, by the pile cluster should be used as bases for added mass computation.

Zerspanbarkeitskennwerte beim Fräsen von Holz

Abstract: Zcrspanbarkeitskennwerte bcim Fr:Ascn wm Massivholz sollen Aufschlul./ iibcr den Zusammenhang zwischen den Einstellbedingungen an der Maschine und den Zelspankr~ilten sowie dem Vcrschlei3 und der Oberfl~.ichenqualitiit gcben. So ist z.B. die Kenntnis des Verschleil3verhaltens einer bcstimmten Werkstoff-Sclmeidstoffpaarung die wcscntliche Grundlage zur Besthnmung kostengi.instigster Einstellbedingungen. Die Gr,36e der ZerspankrLifte wiederum ist Grundlage fiir die Konstruktion dcr Bearbeitungsmasclfinen und die Bemessung yon Antriebsmotoren, Lagerungen usw. Bei der Zerspanung von Massivholz ist der Einflu6 des Werkstoffes l-lolz auf den Zerspanprozel3 besonders grol3, da die Zcrspankriifte nicht nur yon dcr Holzart. sondern sehr wesentlich yon der Faserschnittrichtung, yore Feuchtigkeitsgehall usw. abhLingig sind. Weitere Besonderheiten des Werkstoffcs wie Kern, Splint, Fri.ihholz und SpLitholz. um nur einige atlf/uz:dhlcn, lassen erkcnnen, dab Zerspankr~iftc for Holz mit ciner relativ groi3en Streuung versehen sein mi.isscn.

Feldkurven und Einfluß der Nutung in permanenterregten Synchronmaschinen

Abstract: Ein numerisches Feldberechnungsverfahren wird dazu verwendet, erforderliche Grundlagen zur Berechnung der magnetischen Felder in permanenterregten Synchronmaschinen mit Hilfe vereinfachter Berechnungsmethoden zu ermitteln. Hierzu gehoren in erster Linie die Feldkurven bei glattem Anker. Zur Erfassung des Nutungseinflusses werden zwangslaufig zwei verschiedene Cartersche Faktoren eingefuhrt. Der eine beschreibt das Verhaltnis der Induktion bei glattem zu der bei genutetem Anker und der andere das Verhaltnis der effektiven zur geometrischen Luftspaltlange. Die Kurvenverlaufe einer Hilfsgrose zur Ermittlung dieser beiden Faktoren werden angegeben.

Im Körper gebrochene Knochenplatten — Schadenanalyse und Biomechanik

Abstract: Zwei gebrochene Knochenplatten, die zur Versorgung von subtrochanteren Oberschenkelbruchen eingesetzt waren, wurden untersucht. Die festgestellten Dauerbruche und weitere Einzelheiten der Schadensfalle lassen sich zwanglos durch die Art der Belastung der Platten im Korper erklaren. Eine Abschatzung der Spannungen in den Platten zeigt, das sie lediglich eine frakturstabilisierende Funktion ubernehmen konnen und keinesfalls einer Belastung durch das Korpergewicht ausgesetzt werden durfen. Osteotomy Plates which Failed in Vino — Failure Examination and Biomechanics. Two fractured bone plates, which were used in a subtrochanteric osteotomy, have been examinated. The fatigue failure and additional fracture-characteristics are easily to understand in regarding the stresses, acting in the plates. An evaluation shows, that such a plate should never bear any part of the body weight but should be used only for fracture-fixation.