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289
Because they are laid underground and because their job is to connect widely distant places, pipelines have some particular technical safety features. Chemical industry installations have fixed and instantly recognisable sites. Pipeline routes must be adapted to the constraints of infrastructure and topography, and environmental protection must be taken into account, as well as the possibility that the pipe system may be damaged by external influences. Even minor leakages can have considerable effects on watercourses and the soil, and in many cases, people are also injured. Numerous incidents abroad have proved this. In the recent past, even Germany has not been spared from sudden damage to pipelines. However, not much notice was taken of these incidents, as the resulting damage was minor and there were no fatalities. With hindsight, when seeking the causes of the damage, it is often the case that the rupture of a pipeline is associated with certain recurring features. The scene of the damage is often located near traffic infrastructure. Pipelines must of necessity cross roads and railways or are laid in parallel to such lines of communication. As a result of vibrations caused by traffic, this proximity can lead to ruptures. Road or rail accidents can lead to stresses which pipelines are unable to withstand. But a pipeline failure can have many other causes which cannot be predicted with any certainty and which even show regional particularities. In the interests of safe transport and land planning, it would therefore be worthwhile to be able to evaluate at least the possible consequences in terms of damage that might result from a pipeline rupture. There are hardly any publications on pipeline accidents, at least in German speaking countries; most of what is available is in the form of reports by the fire services. However, these are not sufficient to provide an overview of the situation. For this reason, the Federal Institute for Materials Research and Testing has evaluated many international reports of investigations and publications and summarised what they have to say about the risks inherent in pipeline failures, particularly the damage that results. This report is the outcome of this work.
280
Permeable reactive barriers (PRBs) offer an alternative as opposed to more cost-intensive active methods for groundwater remediation, e.g. pump-and-treat. Long-term performance of PRBs, however, is crucial for the technology’s success. The paper summarises the results of long-term column experiments with elemental iron (Fe0) and hydroxyapatite (HAP) as reactive materials for the removal of uranium from groundwater. Good removal results have been achieved using elemental iron with possible reaction paths being reductive precipitation and adsorption on to corrosion products of Fe0.
277
The use of alternative oils for the lubrication of automobile engines has a potential of ecological and technical advantages. It requires the detailed knowledge of several thermophysical and viscometric properties in a large temperature range (mapping). Therefore, the following properties of up to twenty-eight different oils have been measured in the temperature range from 22 °C to 150 °C: density, heat capacity, thermal conductivity, viscosity at ambient pressure, viscosity under shear rates above 10 6 s-1, and the viscosity at elevated pressures (maximum 100 MPa). The last two have been measured with a substantially improved and a newly developed apparatus, respectively. The pressure- viscosity coefficient has been measured on four hydrocarbon-based, factory-fill oils, a paraffin oil and twenty-three alternative oils. Nine of the alternative oils are based partly or completely on esters, the other fourteen on polyglycols, two of them additionally on water.
272
The international research project HYCREF, funded by the European Commission in the 5 th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soiland waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations a high need exists for certified reference materials for their determination using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: ENpr 14039, water: ISO 9377-2). The experimental conditions and results for preparation and characterisation of a total of nine reference materials (3 water-, 3 soil- and 3 waste materials) are described and discussed. Target values for the reference materials were defined at the beginning of the project in order to have clear quality criteria, which could be compared with the achieved results at the end of the project. These target specifications were related to the maximum uncertainty from test certification exercises (< 5 % for soil/waste and < 10 % for water), the maximum inhomogeneity between bottles (< 3 %) and minimum requirements for stability (> 5 years for soil/waste and > 2 years for water). The feasibility studies showed that solid materials (soil, waste) could be prepared sufficiently homogenous and stable. The test certified values of the 6 solid materials comprise a wide range of mineral oil content from about 200-9000 mg/kg with expanded uncertainties between 5.7-13.1 % using a coverage factor k (k = 2). The development of new water reference materials –the so-called “spiking pills” for an offshore- and a land-based discharge water represents one of the most innovative aspects of the project. The spiking pill technology facilitates the application and storage and improves the material stability compared with aqueous materials. Additional to the preparation and test certification of the reference materials investigations on the analytical method for the determination of mineral oil hydrocarbons were performed. The results obtained in relation to the optimisation of analytical method (extraction procedure, sample pretreatment, clean-up and measurement) were provided to the respective working group of ISO/TC 190, ISO/TC 147 and CEN/TC 292 and were incorporated into the ongoing standardisation procedures. The new version of ISO/FDIS 16703 (July 2004) includes the improvements based on HYCREF results, for example the increase of the solvent/sample ratio, the removal of acetone from the organic extracts and the use of column technique instead of batch technique for clean-up.
268
Tensile testing according to EN 10002-1 is one of the basic mechanical tests to characterise the mechanical properties of metallic materials. This testing procedure has been regularly under development for many decades in order to modify and amend it and to bring it up to an up to date standard. Today tensile testing for quality control in metals manufacturing industry is routinely performed automatically with computer controlled testing machines. Due to economical needs of industry proposals were made by a European Standard Committee to amend the standard EN 10002-1. A European research project with the acronym TENSTAND was started to validate the proposed modifications of the tensile testing standard. The work package 4 of the project was to validate the machine control characteristics. A comparison test program was started with ten partners, 4 test piece geometries and 3 test parameters for 6 materials, partly with upper and lower yield strength and partly with 0.2 % proof strength to compare experimental results according to the proposal to modify the standard EN 10002-1. Initially testing in the strain control mode was introduced as well as switching of the control mode to crosshead control 1 and switching of the testing speed at appropriate points during the test. The comparison test was evaluated statistically and scientifically. The following conclusions were derived from the comparison test and summarised as recommendations to the standard committees. The scatter of the material properties were not significantly reduced by introducing the amended testing procedure. Few of the reasons for the continuously observed scattercan be identified as follows: The material properties are observed to be widely dependent on the testing speed. As a consequence the range for the allowed testing speed must be reduced. The closed loop control was not optimised sufficiently in some tests, the use of complicated testing machine software led to misinterpretation of software commands, individual testing equipment and implementation of the tensile testing procedure led also to scatter of the material properties which lay in a range of few percent. This is blurred by the inhomogeneity of the material.
259
Englische Übersetzung von BAM Forschungsbericht 237! Keramische Werkstoffe haben auf Grund ihrer herausragenden tribologischen Eigenschaften in verschiedenen Bereichen der Produktion Anwendung gefunden und dadurch klassische Werkstoffe verdrängt. Gegenüber Metallen bieten sie bei Mangelschmierung sowohl unter Gleit- als auch grundsätzlich unter Wälzbeanspruchung Schutz vor adhäsivem Versagen. Hohe Herstellungskosten, bedingt bei der Endbearbeitung von Konturen mit verschiedenen und veränderlichen Radien, behindern die breite Marktdurchdringung. Mit der Modellverschleißprüfung - angelehnt an die DIN 50 324 - kann der bearbeitungsbedingte Einfluss auf das tribologische Verhalten unter Wälzreibung untersucht werden.
249
In der vorliegenden Arbeit wird die Ultraschallausbreitung in akustisch anisotropen, homogenen Werkstoffen mit stengelkristalliner Textur wie austenitischen Plattierungen und Schweißverbindungen, austenitischem Guss oder geschweißten Komponenten aus austenitischem Gus modelliert. Die Ergebnisse dieser Arbeit dienen als Vorgabe für Prüfanweisungen und Regelwerke, die besser als bisher an den Prüfgegenstand angepasst sind.
245
Die Reduzierung von Schadstoffen im Grundwasser mit reaktiven Wänden ist eine neuartiges passives Sanierungsverfahren. Die am häufigsten angewandten Dekontaminierungsprozesse sind dabei chemische Reduktion, Oxidation, Ausfällung und Sorption, die im Bericht beispielhaft dargestellt sind. Blei, Chrom und insbesondere Uran werden unter den anorganischen Schadstoffen detailliert behandelt, da solche Grundwasserverunreinigung in vielen europäischen Ländern auftreten. Baumethoden für Dichtwände und reaktive Wände weisen gemeinsame Merkmale auf. Neben den gewöhnlichen Methoden werden Bohrverfahren, deep-soil-mixing, Strahltechnologien, Brunnengalerien, Injektionssysteme und Biobarrieren angewendet, um reaktive Wände zu errichten. Die Technik der reaktiven Wände besitzt ein großes Potential für die Sanierungstechnik der Zukunft.
242
Glühentladung optischer Ausstrahlungsspektroskopie (GDOES) wurde ursprünglich für die elementare Analyse von Größenmaterialien entwickelt. Mehrere Gruppen führten diese Methode zur Analyse von Anstrichen, Laienstapeln und dünnen Filmen durch. In den frühen Neunzigern wurde eine ISO-TC 201-Arbeitsgruppe gegründet, um Normen für alle Formen der Glühentladungsspektroskopie (GDS) zu entwickeln und die Fähigkeiten der Oberflächenchemikalien-Analyse zu beurteilen, insbesondere für die Tiefe von gestuften Systemen. Die Quantifizierung von Tiefenprofilen, d.h. die Umwandlung von Intensitäts-Zeit- Profilen in Konzentrierungs-Tiefen-Profile ist für dc-mode entwickelt worden. 1997 wurde ein VAMAS TWA 2 Vorschlag für ein Referenzanstrich für GD-OES Tiefe gemacht. Entsprechend dem VAMAS Beurteilungsverfahren wurde dieser Vorschlag 1998 mit einigen geringfügigen Änderungen genehmigt.
235
The present work is focused on the study of the spectroscopic and complexometric behavior of different ion-sensitive fl uorescent probes. Three of the four types of probes studied follow a conventional principle of signal generation and their molecular constitution corresponds to either a fl uorescent ligand ( BP(OH)2), so-called intrinsic charge transfer (ICT) fl uorescent probes (donor- acceptor-substituted chalcones), or electron transfer (ET) fl uorescent probes (substituted triaryl-Δ2- pyrazolines). The latter two systems are designed in a modular way and thus, both the signal generating fl uorophore and the complexing receptor can be carefully tuned. Whereas in the case of the ICT probes both units are electronically conjugated, these moieties are more or less electronically decoupled in the ET probes and signal generation is based on the modifi cation of a long range electron transfer process. The fourth type of probe investigated, a boron dipyrromethene derivative (BDP), is also designed in a modular way. But here, due to the highly pretwisted constitution of the molecule, fl uorophore and receptor are only “virtually” decoupled. Besides employing this alternative mechanism of signal generation, control of the selectivity by carefully directed receptor design and improvement of the selectivity and sensitivity of fl uorometric metal ion analysis by recording time resolved emission spectra (TRES) were the main aims of these investigations. Furthermore, with the aid of various model compounds, NMR spectroscopy as well as quantum chemical calculations, a fundamental understanding of the photophysical behavior of the different classes of dyes was obtained. In accordance with its parent compound 2,2‘- bipyridyl, the fl uorescent ligand BP(OH)2 shows complexation induced changes of its absorption and emission behavior in the presence of heavy and transition metal ions. Whereas paramagnetic ions such as CuII or NiII (and also HgII) lead to static fl uorescence quenching, the diamagnetic ions ZnII and CdII form strongly fl uorescent complexes with ion specifi c fl uorescence lifetimes in the ns time range. Both complexes are stable in the excited state which is manifested by a strongly reduced rate constant of non radiative deactivation compared to that of the free ligand. Both the absorption and emission spectra of the complexes largely overlap and a discrimination with steady-state fl uorometry is very limited. Nevertheless, with time resolved fl uorometry a separation of both components is possible and for a series of synthetic ZnII/CdII containing samples this gain in selectivity by global analysis of the time resolved emission spectra (TRES) could be demonstrated. The intrinsic fl uorescent probes of chalcone type contain a cation selective receptor in the donor part of the molecule and show a strong decrease of the intramolecular charge transfer process due to complexation induced weakening of the donor. Depending on molecular probe design and solvent polarity, the fl uorescence of the uncomplexed molecule occurs either from a polar directly exicted (E*) or a highly polar charge transfer state (A*) which is populated via an excited state reaction involving single bond twisting. Here, competing processes include population of a non emissive polar (K*) or weakly polar (P*) transient state. Furthermore, the fl uorescence of these dyes can be quenched by energetically close lying nπ* states (in apolar solvents) or by enhanced internal conversion due to the decreasing energy gap between ground and excited state (in highly polar solvents). As mentioned above, the donor strength is reduced upon cation complexation in polar solvents and a moderate fl uorescence enhancement occurs. Besides increased fl uorescence quantum yields, this effect results in ion specifi c fl uorescence lifetimes of the complexes. Upon exchanging the aza oxa for an aza thia macrocycle in the receptor part of the system, the cation selectivity could be tuned from alkali and alkaline earth metal ions to the thiophilic metal ions AgI and HgII. Here, especially the fl uorescence enhancement in the presence of the well-known quencher HgII is analytically valuable. Upon cation binding the ET probes of the triaryl-Δ2-pyrazoline type show very small spectral shifts but much larger fl uorescence enhancement compared to the ICT probes. Again, by problem specifi c use of different receptors, the selectivities can be controlled. Based on a detailed investigation, for the 5-p-N,N-dialkylanilino-3-benzthiazol-1-phenyl-Δ2-pyrazolines, the intramolecular processes which lead to fl uorescence quencing in the unbound state and “switching on” of the fl uorescence in the complexed state could be identifi ed. For these molecules, the intramolecular charge transfer in the basic chromophore occurs in the sub ps time range and is quenched by an electron transfer process from the largely electronically decoupled receptor to the acceptor part of the basic chromophore on the ps time scale in highly polar solvents. “Virtually” decoupling fl uorophore and receptor in the BDP derivative fi nally makes it possible to yield extremely high complexation induced fl uorescence enhancement signals. For these highly pretwisted donor acceptor biaryls, the directly excited emissive state (LE) forms a highly polar, twisted charge separated charge transfer state (CT) in polar solvents. Emission of the latter is strongly forbidden and, depending on solvent polarity, is largely red shifted compared to the LE fl uorescence. Thus, a largely separated dual fl uorescence is already observed in solvents of medium polarity and in highly polar solvents both fl uorescence bands are nearly completely quenched. Metal ion complexation blocks off the CT process and leads to a “switching on” of the LE emission yielding fl uorescence enhancement factors > 1000. This process is so sensitive that for most of the cation complexes studied, two emissive complex conformers with strongly overlapping absorption and emission spectra occur which could be distinguished by their fl uorescence lifetimes.