Magnetic search coil system for linear detection ofthree-dimensional angular movements

The design of a two-dimensional (2D) magnetic field search coil system based on the phase detection principle is described. The system was developed to record horizontal and vertical eye and head movements of small, unrestrained laboratory animals. It is also applicable for measuring three-dimensional (3D) eye and head movements in primates and man. The output is linear over 355 degrees in the horizontal plane and over +/- 60 degrees in the vertical direction. The procedure of recording 3D eye and head movements is discussed.     

Skin- und Proximity-Effekt bei Leitungen unterschiedlicher Querschnittsform

Übersicht Für Leitungen unterschiedlicher Form der einzelnen Leiter-Querschnitte werden in Abhängigkeit von Leiterabstand und Frequenz die Impedanzen und insbesondere die Verluste ermittelt, auch die Stromdichteverteilung wird dargestellt. Die Berechnung erfolgt mit der Methode der finiten Elemente.

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Skin- and proximity-effect in transmission lines of different cross sections

Contents Impedances and especially losses are calculated for transmission lines of different cross section of the particular conductors as a function of their distance and the frequency. The distribution of the current density is obtained. The finite-element-method is applied.

     

Künstliche Intelligenz auf dem Fußballplatz

Dieser Artikel beschreibt, worum es sich beim RoboCup und bei Studienprojekten handelt. Au?erdem stellt er exemplarisch die Roboter und Software des Teams CoPS Stuttgart vor.     

History of autologous blood transfusion in the 19th century]

Autologous blood transfusion in animal experiments was performed already in the first half of the 19th century. These experiments, however, were not conducted to explore the feasibility of autologous blood transfusion in man, but provided only the experimental design for physiological investigations on the defibrination of blood. Blood withdrawn from the animals by phlebotomy in these experiments was retransfused either with or without defibrination. The idea of retransfusing the patient's own blood was mentioned for the first time by Eulenburg and Landois, when in 1866 they proposed to treat gas poisonings with a type of exchange transfusion (transfusion with simultaneous depletory bleeding). They suggested that the blood that would be withdrawn could be retransfused after the poisonous gases had been eliminated. The first who demonstrably considered the possibility of autologous blood transfusion in operative medicine was the Halle surgeon Richard von Volkmann in 1868. The first originally sourced autologous blood transfusion, however, was performed by the Kiel surgeon Friedrich von Esmarch who, in a case of exarticulation of the thigh at the hip joint, collected the blood that had been shed during the operation in a washbowl, defibrinated it, and reinjected it into the severed femoral vein. However, despite some further cases of autologous blood transfusion performed for various indications and in different countries, the method was unable to gain a foothold in the treatment of acute blood loss, and fell into oblivion until the Leipzig gynaecologist Johannes Thies revived interest in it in 1914. The authors surmise that the advantages of autologous blood transfusion had not been recognised in the 19th century.     

Koordinatentransformationen zur Behandlung von Mehrphasensystemen

Übersicht In der elektrischen Energietechnik wird die Lösung von Netzproblemen durch Anwendung von Koordinatentransformationen erleichtert. Dabei werden Symmetrieeigenschaften elektrischer Betriebsmittel ausgenutzt.Die möglichen Transformationen werden hergeleitet. Man stellt fest, daß die bekannten o (Clarke)-, odq (Park)- und o12 (symmetrische)-Komponenten noch um die neu vorgestellten oGH-Komponenten zu ergänzen sind, um ein vollständiges System von Transformationen zu erhalten. Die oGH-Komponenten präzisieren den in der Literatur eingeführten Begriff Raumzeiger.Die richtige Wahl des Komponentensystems ist entscheidend für die Nutzung der möglichen Rechenvorteile. Kriterien für die geeignete Auswahl werden angegeben.

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Contents The solution of network problems in power engineering is often simplified by the use of coordinate transformations. These transformations take advantage of the symmetrical properties of electrical equipment.All possible transformations are deduced in this paper. It is found that the well-known o-(Clarke)-, odq-(Park)- and o12-(symmetrical)-coordinates have to be supplemented by certain oGH-coordinates to form a complete set of transformations. These oGH-coordinates generalize the concept of the complex vector as known in the literature.The proper choice of the coordinate system is essential for the efficient use of these transformations. Criteria for the proper choice are given.

     

Acidization—II. The dissolution of calcite in hydrochloric acid

The dissolution of calcite in hydrochloric acid was studied with the aid of a rotating disk system at 800 psig in the temperature range ?15·6–25°C. At 25°C the dissolution process is mass transfer limited even at high disk rotation speeds whereas at ?15·6°C both mass transfer and surface reaction rates limit the dissolution rate. The multicomponent coupled ionic diffusive fluxes of reactants and products were defined by using the gradient of the electrochemical potentials as driving forces for the diffusion. The activity coefficients used in calculating the multicomponent diffusivities of the diffusing species were estimated by Harned's rule. The concentration profiles of the ions in the boundary layer were then determined by numerically integrating the system of coupled convective diffusion equations. The effects of variable density, viscosity, and high mass fluxes on the fluid velocity in the boundary layer were taken into account. The rate of the surface reaction was found to be proportional to the 0·63 power of the surface hydrochloric acid concentration. Analysis of the experiments suggests that the absorption of hydrogen ion (described by a Freundlich adsorption isotherm) on the solid calcite surface and subsequent reaction of the adsorbed hydrogen ion with the solid calcite matrix is the reaction mechanism.     

1 Gbit/s transmission experiment over 101 km of single-mode fibre using a 1.55 ?m ridge guide C3 laser

Using a cleaved-coupled-cavity (C3) ridge guide laser which oscillates in a single longitudinal mode at 1.55 ?m wavelength, we report the first lightwave transmission experiment exploying single-frequency lasers at speeds above 500 Mbit/s. We have achieved digital transmission with a bit-error rate of 2 × 10?10 at 1.0 Gbit/s over 101 km of single-mode fibre. This represents a record for the length of unrepeatered optical transmission for bit rates greater than 500 Mbit/s. Evidence for an error-rate floor, presumably due to residual partition noise, is observed. No such floor was observed in an 84 km?1 Gbit/s experiment using the same C3 laser.     

Linear and nonlinear optical properties of some ternary selenides

The refractive indices of the ternaryA^{I}B^{III}C_{2}^{VI}semiconductors CuAlSe2, AgGaSe2, CuGaSe2, and AgInSe2have been measured over most of the transparency range of these crystals. The optical nonlinear coefficients for second-harmonic generation of AgGaSe2CuGaSe2, and AgInSe2have also been measured. Three-frequency colinear phase matching is analyzed in detail for AgGaSe2. The birefringences of the other three crystals are not sufficient to permit three-frequency colinear phase matching within the range of the measured index. The merits of AgGaSe2for nonlinear optical applications are evaluated in comparison with other promising infrared nonlinear materials.