New thermoelectric components using microsystem technologies

This paper describes the first thermoelectric devices based on the V-VI-compounds Bi/sub 2/Te/sub 3/ and (Bi,Sb)/sub 2/Te/sub 3/ which can be manufactured by means of regular thin film technology in combination with microsystem technology. Fabrication concept, material deposition for some 10-/spl mu/m-thick layers and the properties of the deposited thermoelectric materials will be reported. First device properties for Peltier-coolers and thermogenerators will be shown as well as investigations on long term and cycling stability. Data on metal/semiconductor contact resistance were extracted form device data. Device characteristics like response time for a Peltier-cooler and power output for a thermogenerator will be compared to commercial devices.     

Optimization of a contact surface

The paper introduces ideas from shape optimization to multibody system dynamics. A disk rolling down a given slope is taken as a simple example, for which it is the goal of the optimization to shape the rolling contour of the disk such that it takes a minimum time to cover a certain distance. The shape of the contour is described by its radius of curvature. The governing equations of motion result from the kinematics of relative motion and the Newton–Euler formalism. Three different kinds of spirals are defined and optimized.     

Actinic brachial plexus lesion

OBJECTIVES: To prove or disprove this assumption that in neuropathy patients with abundant spontaneous activity, peak-ratio interference pattern analysis may lead to false negative results. METHODS: Spontaneous activity >100 microV, automatically analysed by turn/amplitude analysis and expressed as (turns/second)/2 ((T/S)/2), and interference patterns, analysed by the peak-ratio technique, were recorded, one after the other, from the right anterior tibial muscle of 21 patients with neuropathy, aged 36-87 years. RESULTS: The mean number of spontaneous discharges ((T/S)/2) was 12.3 (range 5.5-26) and its mean amplitude 261 microV (range 146-478 microV). Despite this abundant spontaneous activity, peak-ratio analysis was neurogenic in 81% of the patients. All peak-ratio parameters were independent on the amount and amplitude of spontaneous discharges. CONCLUSIONS: Spontaneous discharges >100 microV could be adequately assessed by means of the turn/amplitude analysis and did not influence peak-ratio analysis in neuropathies.     

Fluid flow and mixing in secondary metallurgy

Mixing in metallurgical vessels is determined by bulk flow, turbulence and diffusion. In this presentation, the main features of mixing liquid steel by gas stirring are discussed. The criteria for bubbling and jetting during gas injection are considered including interaction of powder load on flow regimes. It is of interest to know the domains of bubbling and jetting behaviour in order to minimize the effect of back attack which is responsible for additional wear of bottom linings and tuyere pipes. Quantitative information is given on velocity, the radius and the pumping capacity of the buoyant plume. The relations lead to the conclusion that the gas flow should be apportioned to two or more plugs in order to increase the efficiency of the pumping effect. Furthermore, the macroscopic flow pattern is substantially influenced by the ratio of height to diameter of the ladle. Especially at high ratios dead volumes near the ladle bottom are observed. Further examples for the influence of fluid flow on reactions, dispersing and separating in the ladle and tundish are given. At first approach, mixing time depends on the gas flow rate or on the specific power input. But the details are much more complicated. It is shown that the mixing process can be described by two types of models among others: the turbulent recirculation model and the model of partial volumes. The comparison of calculated concentration-time-dependencies with plant results confirms the practicability and usefulness of the model of partial volumes. It is also concluded that the water model results for ladles may be transferred to plant conditions. In total all examples that are discussed emphasize the great significance of model simulations and model calculations as instruments for process improvement and process development.     

Phasengleichgewichte des Schnittes FeOn–CaO im Dreistoffsystem FeO–Fe2O3–CaO bei Eisensättigung

Überprüfung der Schmelzgleichgewichte des Dreistoffsystems FeO–Fe₂O₃–CaO auf der wüstitreichen, eisengesättigten Seite des Systems. Angaben über die Ergebnisse der thermischen Analysen, isothermen Halteversuche und mikroskopischen Untersuchungen. Aussagen über den quasibinären Schnitt Eisen-Kalkferrit bei Temperaturen unter 1150 °C sowie über den quasibinären Schnitt Calciowüstit-Kalk über 1150 °C.     

Development of a reduction process and test results of the reduction equilibria of wustite as a function of oxygen content and temperature

A new measurement technique allows the continuous measurement of the oxygen contents of the wustite as a function of temperature without having to pass through the disintegration of the wustite to iron and magnetite and have the accompanying problems during the chemical analysis by cooling the sample. Measurements are carried out in form of isothermal oxygen reduction tests, starting with pure Fe₂O₃ in a thermogravimetric balance with an upstream gas mixer which, operating with CO₂/CO gas mixtures, ensures a graduation of the input reduction potential CO'₂ in steps of 1%. Simultaneous weighing of the test material sample permits, by means of the measured weight loss and relation to the charged amount of Fe₂O₃, a very accurate measurement of the oxygen concentration within the test material at any point in time during testing. Testing was carried out along these lines in the range between 700 and 1300°C. The results show that, at constant temperatures, the wustite oxygen contents decrease linearly from the right- to the left-hand boundary of the wustite field, with the oxygen pressure of the gas phase (log p_CO2/p_CO or log pO₂). When comparing these results with the findings of Darken and Gurry, a difference becomes apparent in the curves of the log pO₂ values as a function of the temperature. While our own curves are substantiated by very many measured values, the curves of Darken and Gurry are based on only twenty-three values at four different temperatures. Based on this result, systems of equations are developed which describe the homogeneous field of the wustite in the Fe-O-C reduction system without any gaps. An equivalent system of equations can also be developed from the values of a literature evaluation carried out by Giddings and Gordon. The curves resulting from the two equations do not differ very greatly. But the differences are large enough for corresponding variances to be expected when establishing the wustite boundaries and, thus, the position of the wustite field in the phase diagram.     

Stoffumsatz bei diskontinuierlichen und kontinuierlichen Stahlerzeugungsverfahren

Bedeutung kontinuierlicher Verfahren. Stoffumsatz im diskontinuierlich betriebenen Reaktor. Grenzflächenvergrößerung durch Emulgierung der Phasen. Kontinuierlicher Gleichstromreaktor. Verweilzeitspektrum von einem Reaktor und von Reaktorkaskaden. Stoffumsatz in der Reaktorkaskade. Stoffumsatz im Gegenstrom ohne und mit Rückvermischung. Übergangsfunktion einer 6 m langen elektromagnetischen Gegenstromrinne. Abschätzung des Grenzflächenvergrößerungsfaktors. Einfluß der Tropfenverteilungen zwischen Schlacke und Metall.