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Hannover, Germany

Siwek R.,GmbH GmbH
Chemical Engineering Transactions | Year: 2012

In December 2008 the VDI-Guideline Part 8: 2008 was published. In this guideline the basic information regarding fire and explosion risks, fire and explosion protection measures are given and aims both the manufacturer's and the user's tasks. In March 2011 the new the VDI-Guideline Part 8.1: 2011 was published. The main information contains examples of preventive fire and explosion protection and constructional measures for fire and explosion protection in elevators. Thanks to the results of extensive explosion trials on a bucket elevator conduced in the last years, important gaps in our knowledge have been filled and new findings regarding explosion venting and explosion suppression gained. These findings are also incorporated in this new guideline Part 8.1. Equations involving numerical values have been developed which represent an optimized mathematical matching of the innumerable experimental investigations, and which, as experience has shown, embrace the conditions of operational practice even for the most unfavourable cases. Both guidelines are the basic for a European standard in form of a Technical Report on explosion protection on elevators. Copyright © 2012, AIDIC Servizi S.r.l. Source

Klein R.,University of Regensburg | Zech O.,University of Regensburg | Zech O.,GmbH GmbH | Maurer E.,University of Regensburg | And 2 more authors.
Journal of Physical Chemistry B | Year: 2011

Recently, a new family of ionic liquids based on oligoether carboxylates was introduced. 2,5,8,11-Tetraoxatridecan-13-oate (TOTO) was shown to form room-temperature ionic liquids (RTILs) even with small alkali ions such as lithium and sodium. However, the alkali TOTO salts suffer from their extremely high viscosities and relatively low conductivities. Therefore, we replaced the alkali cations by tetraalkylammonium (TAA) ions and studied the TOTO salts of tetraethyl- (TEA), tetrapropyl- (TPA), and tetrabutylammonium (TBA). In addition, the environmentally benign quaternary ammonium ion choline (Ch) was included in the series. All salts were found to be ionic liquids at ambient temperatures with a glass transition typically at around -60 °C. Viscosities, conductivities, solvent polarities, and Kamlet-Taft parameters were determined as a function of temperature. When using quaternary ammonium ions, the viscosities of the resulting TOTO ionic liquids are >600 times lower, whereas conductivities increase by a factor of up to 1000 compared with their alkali counterparts. Solvent polarities further reveal that choline and TAA cations yield TOTO ionic liquids that are more polar than those obtained with the, per se, highly polar sodium ion. Results are discussed in terms of ion-pairing and structure-breaking concepts with regard to a possible complexation ability of the TOTO anion. © 2011 American Chemical Society. Source

Wenzel H.,GmbH GmbH
Proceedings of the Institution of Civil Engineers: Forensic Engineering | Year: 2016

The ancient Greek saying ‘Scio nescio’, ‘I know I don’t know’ (by Socrates, commonly used in its Roman version), applies in structural engineering despite the impression that civil engineers perfectly understand the behaviour of their structures. Failures often hit them by surprise and very often they face more questions than answers. In this environment, forensic engineering helps them understand the performance of structures by using new technologies and materials. They also find that the current standards and practices do not cover all the complexity, record dimensions and non-linear behaviour of the built environment. It is most appropriate to learn from failures, disseminate this information widely and educate the engineering community. With changes in engineering education and often applied standard solutions, the risk of misconception increases. This paper provides an opinion on current practice and informs about the development approaches taken in various regions of the world. © 2016, Thomas Telford Services Ltd. All Rights Reserved. Source

Starck H.,GmbH GmbH
Metal Powder Report | Year: 2010

A study carried out by German hardmetals specialists H C Starck has shown that one of the necessary conditions for improvement is proper choice of the binder alloy composition. Hardmetals were prepared from a WC 0.6 μm by wet milling in ethanol, followed by vacuum drying. In order to compensate for the lower density of the Fe containing alloys compared to Co, the hard metal formulations were changed by weight proportions in order to keep the volume fraction of the binder alloy comparable to WCC08. In addition, K40 hardmetals were prepared from a WC 0.8 μm with 12% Co and 10.4% of a Co-free FeNi binder alloy FeNi 82/18. The hardmetal powders were pressed and sintered in vacuum or in a sinter HIP, if residual porosity was above A02 after vacuum sintering. Unmounted pieces were prepared for hot hardness measurement. The FeNi 82/18 dissolves only carbon, and shows a clear dependence of hot hardness from carbon content at all temperatures until 800°C, but shows a lower hot hardness at 600°C. Source

Paschotta R.,GmbH GmbH
Photonics Spectra | Year: 2014

Researchers share their views on how optical fibers work in different applications with supporting numerical simulations to conduct related investigations. One of the most basic elements in the analysis of optical fibers is the critical angle for reflection at the core/cladding interface. Total internal reflection can occur only if light incident on the fiber end propagates with angles against the fiber axis that are below the critical angle. The overall coupling loss of that fiber joint depends on the distribution of powers over the modes of the input fiber. There are also various surprising features for coupling between single-mode fibers. The coupling loss for any direction of propagation is determined simply by an overlap integral of the two mode functions. Source

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