Measuring of the quenching effect of liquid hardening agents on the basis of synthetics

To judge liquids for steel hardening, normally special test specimens are quenched by means of immersion. Characteristics are taken from temperature-time curves, which are picked up in the sample center. These characteristics (i.e. temperature of transition from filmboiling to nucleate boiling – LEIDENFROST-Temperature – and cooling rates) serve as criterions for the judgement of quenching effect. The effect of sample characteristics (geometry and material) upon characteristic values of the cooling curve was determined. Hence a proposal to design a test specimen was derived. This specimen (Chromenickel-steel-cylinder, diameter 15 mm, length 45 mm, rounded edges) presents of all examined configurations a very good possibility to a precise judgement of quenching media as well as chances to estimate the quenching process in case of steel hardening. As common quenching tests (with a single – central – hot junction) do not allow to draw conclusions referring to steel hardening, an additional method was developed to calculate the surface-temperature dependent heatflux density (respectively heattransfer coefficient) from three temperature-time-curves, measured on different radii of the sample cylinder. The reliability of this method was proved (differential method according to Binder-Schmidt).     

Two-dimensional digital filters for geophysical applications: A simple design method leading to an easy implementation

A simple procedure for the design of two-dimensional digital filters will be presented. Its main interest is in the field of geophysical signal processing, since the design implies in these cases simple structures for the implementation. The 2-D problem is reduced to one, two or complicated cases to several 1-D problems. By 3 examples, relevant in geophysics, the power of this method will be demonstrated. The design is applicable for arbitrary ideal frequency responses, however the simple realization will be lost in general. The result is a suboptimal filter, which can be used, if desired, as an initial solution for an L_∞-approximation. However, the efficiency of the presented method is established by the fact that the design and implementation go hand in hand and are adapted to the special problem under consideration.     

Direct reduction and smelting reduction – an overview

A survey is given on the current state of direct reduction and smelting reduction processes. Several developments, such as coal injection, top-gas recycling etc., contribute to decrease the coke consumption in the blast furnace. Coal-based as well as gas-based direct reduction processes have not succeeded in Western Europe. These processes have only attracted economical interest in locations where there is a cheap source of energy. Other developments to reduce iron ore are concerned with the direct production of liquid iron in a smelting reduction process with a substantial part of the reduction taking place in the liquid oxide phase. The ideal concept of a smelting reduction process with direct use of fine ore and coal as well as only liquid state reduction to a liquid product similar to steel has not yet been realized.     

A safe transmission line for MRI

Magnetic resonance imaging (MRI) has been established as a reliable and safe imaging method for the human body. However, electric conductors, such as cables situated near or in the human body, should be avoided because induced currents in the cables can cause hazardous heating in the surrounding tissue. In this paper, a new principle for the design of a transmission line is introduced and demonstrated, which is capable of avoiding dangerous heating of cables. The principle is based on transformers placed along the line, splitting the long line into several short not resonant and thus safe sections. A transformer design is introduced along with the theoretical aspects for both the avoidance of the undesired induced currents and the reduction of signal attenuation. Furthermore, the design fulfills the geometrical requirements of the side lumen of a standard catheter. Matching networks, whose elements are determined by power matching, are used to reduce signal attenuation by the transformers. A prototype was built to validate both theory and the simulations. As demonstrated in this work, it is possible to build safe transmission lines for MRI, making applications such as active catheter tracking possible. We expect that even new applications, such as safe intravascular imaging will be possible in a safe manner in the future.     

Dynamic and Formal Verification of Embedded Systems: A Comparative Survey

Embedded Systems, by their nature, constitute a meeting point for communities with extremely different background. In particular, the high demands for quality and reliability for embedded systems have led to complementary quality assurance efforts: hardware engineers have developed techniques for dynamic verification in terms of co-simulation, which, in particular, addresses the different nature of hardware and software components. Thus these techniques are tailored for the transactional level, which comprises dedicated models for the hardware and the software parts. On the other hand, there is a bulk of work on formal verification techniques, which typically address higher levels of abstraction. These techniques are exhaustive in the sense that they cover all the infinite possible paths of their models, however at the price of neglecting many of the low-level aspects treated by co-simulation. It is the goal of this paper to increase the mutual understanding between these communities and to animate research at this exciting borderline.     

Piezoelectric two-layer stacks of cellular polypropylene ferroelectrets: transducer response at audio and ultrasound frequencies

Piezoelectric cellular polypropylene films, so-called ferroelectrets, are assembled in a stack with two active transducer layers. The stack is characterized with respect to its linear and quadratic response in a frequency range from 1 kHz to 80 kHz. A relatively smooth frequency response in the sound-pressure level is found for the individual layers as well as for both layers driven in phase. The piezoelectric response of the two-layer stack is twice the response of an individual layer over a rather broad frequency range. Furthermore, the influence of the preparation conditions on the resonance frequency and the effect of the quadratic distortion on the radiated sound are investigated both for the individual transducer films in the stack and for the stack system as a whole.     

Enzymatic Formation and Physico-Chemical Behaviour of Uncommon Monoglycerides

Results on the enzymatic monoacylation of glycerol by aid of phenylboronic acid in organic solvents are presented. The comparison of two alternative methods indicates that the ?2-step-method”? (synthesis in one batch unit without isolation of intermediates) is in total more favourable than the ?3-step-method”? (synthesis in two batch units including isolation of intermediates), although yields are somewhat lower. Probably this disadvantage originates from an enzyme inhibition caused by residual free phenylboronic acid in the reaction system. Several varying uncommon fatty acids like (S)-17-hydroxyoctadecanoic acid, 12-hydroxyoctadecanoic acid and 2-hydroxyhexadecanoic acid have been used as oleo-components. As far as no steric hindrance is caused by these substrates, product formation is about 80% (basis ?2-step-method”?). Investigations at the Langmuir film balance showed different film states with specific transition phases for the 1(3)-(17-hydroxy)-octadecanoyl and the 1(3)-(12-hydroxy)-octadecanoyl glycerol. The monoglyceride of the 2-hydroxyhexadecanoic acid proved to be a good emulsifier. Its qualities in this respect were confirmed by the data of the surface and interfacial tension versus n-hexadecane and also by the outcome of the emulsification tests. The enzymatic acylation of a diol like 1,3-propanediol led to the 1-(17-hydroxy)-octadecanoyl-3-propanol (yield: 50%). The film behaviour of this ester was similar to that of the corresponding monoglyceride.     

Dynamische Selbstoptimierung der Drehbearbeitung

Zusammenfassung Entwickelt wurde eine Funktionserweiterung für CNC-Steuerungen an Drehmaschinen, die eine dynamische Schnittwertplanung und-steuerung nach technischen und organisatorischen Kriterien gestattet. Für diesen Optimierregler werden die aus einem entsprechenden mathematischen Modell abgeleiteten Algorithmen und seine Verbindung zur NC-Programmierung angegeben. Mittels weiterer Modelle wird auch eine integrierte Standzeitplanung und-steuerung bei wechselnden Schnittbedingungen dargestellt. Mit solchen Proze?regelkreisen für Schnittwerte und Werkzeugstandzeiten k?nnen erstamalig auch fertigungsorganisatorische Plandaten durch die CNC-Steuerung verarbeitet werden. Gleichzeitig werden in Untersetzung der Werkstattsteuerung St?rungskompensationen „vor Ort” m?glich.