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Eingeladener Vortrag
- nein (73)
Aus wirtschaftlichen, konstruktiven sowie ästhetischen Aspekten werden moderne Stahlbaukonstruktionen immer schlanker und leichter ausgeführt. Dazu werden zunehmend hochfeste Feinkornbaustähle mit Dehngrenzen ≥ 690 MPa eingesetzt, wodurch eine Gewichtsreduzierung von 30 % bis 50 % und eine Kostenersparnis von 5 % bis 15 % erreicht werden kann.
Das Potential hochfester Feinkornbaustähle ist unter Beachtung der heutigen Richtlinien und Regelwerke jedoch nicht ohne weiteres nutzbar. Durch das Forschungsvorhaben wurde der Einfluss der Wärmeführung auf die Eigenspannungsausbildung und Kaltrissbildung unter Berücksichtigung realitätsnaher Steifigkeitsbedingungen untersucht. Auf der Grundlage dieser Erkenntnisse wurde ein Beitrag zur Verbesserung der Verarbeitungsrichtlinien erarbeitet, welche dem Verarbeiter eine sichere schweißtechnische Verarbeitung bei verbesserter Ausnutzung der Materialeigenschaften ermöglicht. Vor allem die Tragfähigkeit und die Sicherheit der Schweißverbindung bestimmen die Bemessung der Konstruktion und somit den nachhaltigen und ökonomischen Einsatz dieser Güten. Der Zusammenhang zwischen der Höhe der entstehenden Eigenspannungen und der Wärmeführung in realen Konstruktionen ist zurzeit nur qualitativ überschaubar und führt zu einer eher konservativen Auslegung heutiger Schweißkonstruktionen. Die wirtschaftliche Verarbeitung hochfester Stähle wird neben dem Erreichen anforderungsgerechter mechanischer Eigenschaften im Schweißnahtbereich vor allem durch die Vermeidung von Kaltrissen bestimmt. Die diesbezüglichen Empfehlungen in den geltenden Regelwerken beruhen jedoch vornehmlich auf Erkenntnissen aus Laborschweißungen an Kleinproben unter freier äußerer Schrumpfung. Die Hauptursachen für die Entstehung von Eigenspannungen wie inhomogene, lokale Erwärmung und Abkühlung der schweißnahtnahen Bereiche und insbesondere die konstruktive Schrumpfbehinderung infolge umgebender Montagegruppen werden damit jedoch nicht abgebildet. Der Einfluss der Wärmeführung, insbesondere der lokalen Vorwärmung, auf die Eigenbeanspruchung einer Konstruktion ist derzeit weitgehend unbekannt.
Ziel des Forschungsvorhabens war es, den Einfluss der Wärmeführung auf die Eigenspannungsausbildung in geschweißten Konstruktionen zu quantifizieren sowie Aussagen zur Beeinflussung und Absenkung der Eigenspannungen und somit der Gesamteigenbeanspruchung von Schweißkonstruktionen zu erarbeiten. Dazu wurden durch die sukzessive Steigerung des Einspanngrades der Zusammenhang zwischen Wärmeführung und resultierender Eigenspannung unter zusätzlicher Schrumpfbehinderung geklärt. Ferner wurde die Übertragbarkeit der den Regelwerken zugrundeliegenden Kleinprobenergebnisse auf reale Konstruktionen untersucht. Mithilfe systematischer Klein- und Großlastschweißversuche an definiert schrumpfbehinderten Proben konnte der Einfluss der Wärmeführung sowohl auf die lokalen nahtnahen Eigenspannungen als auch globale Eigenbeanspruchungen durch Reaktionsspannungen analysiert werden. Es zeigte sich, dass eine Reduktion der lokalen Eigenspannungen und der Eigenbeanspruchung von geschweißten Konstruktionen durch eine geringere Wärmeeinbringung möglich ist. Eine Absenkung der Zwischenlagentemperatur erwies sich dabei unter anderem als besonders günstig. Damit ist es möglich vorhandene Wärmeführungskonzepte für hochfeste Stähle zu optimieren und dadurch die Kaltrissbildung zu vermeiden.
Ziel dieser Arbeit war die Entwicklung einer Methode zur Hochdurchsatzanalyse von partikelgebundenen Split-and-Mix-Peptidbibliotheken. Dabei wurde ein System entwickelt, das Partikelbibliotheken in kurzer Zeit auf ihre Bindung zu einem Zielmolekül hin untersucht und im nächsten Schritt eine direkte „Ein-Partikel“-Sequenzierung der Peptide von der festen Phase ermöglicht. Die Analyse der Bindung eines Zielmoleküls an ein selektiv bindendes Peptid wurde dabei in einem Modellsystem simuliert. Dazu wurde FITC-markiertes Neutravidin 3 mit festphasengebundenen biotinylierten und nicht-biotinylierten Peptiden inkubiert. Die Bindung von Neutravidin-FITC an die biotinylierten Peptide konnte erfolgreich mittels eines Fluoreszenzmikroskops nachgewiesen werden, wobei diese Methode für eine Hochdurchsatzanalyse ungeeignet war. So wurde die Analyse des Fluoreszenzassays auf einen Microarrayscanner übertragen (siehe Abbildung 33). Dies gelang erfolgreich wobei die hohe Eigenfluoreszenz des Tentagel-Harzes zu falsch positiven Ergebnissen führte. Mit einem Wechsel zum längerwelligen Fluoreszenzfarbstoff ATTO-633 konnten falsch positive Ergebnisse vermieden werden. Somit wurde die zeitintensive Fluoreszenzanalyse von einem Fluoreszenzmikroskop erfolgreich auf einen Microarrayscanner übertragen, welcher in kurzer Zeit (ca. 5 min pro Objektträger) eine Vielzahl an peptidbeladenen Partikeln gleichzeitig analysieren kann.
Dieses Dokument fasst den Projekfortschritt des BAM-Projektes "Ermittlung geeigneter Wärmeführungen zur Wasserstoffreduktion beim Schweißen höherfester Feinkornbaustähle mit modifiziertem Sprühlichtbogen" im Rahmen des Fachausschusses 1 "Schweißmetallurgie & Werkstoffverhalten" des DVS e. V. zusammen.
Hausmüllverbrennungsasche (HMVA) hinsichtlich der Menge und der Qualität generierter Fraktionen optimiert. Die Optimierung wurde vom Projektpartner Evers und Co. GmbH durchgeführt. Neben der für die Wirtschaftlichkeit relevanten Rückgewinnung von Metallen stand die Qualität der mineralischen Fraktionen im Vordergrund. Die Mineralik stellt mengenmäßig den größten Anteil an HMVA dar und sollte weitestgehend für einen möglichen Einsatz als Baustoff nutzbar gemacht werden. Dafür musste insbesondere der Chlorid- und Sulfatgehalt reduziert werden. Gut wasserlösliche Substanzen können durch die nass-mechanische Aufbereitung über das Prozesswasser ausgetragen und unerwünschte Elemente im Filterkuchen angereichert und entsorgt werden.
Quo Vadis – Kurzdarstellung
Im Fokus von Quo Vadis stehen die Qualitätssicherung von Verbundwerkstoffen und die Validierung der Zentrifugentechnologie zur quantitativen Bestimmung von Festigkeitswerten in der Beanspruchung auf Zug als Mehr-Proben-Prüfverfahren unter Verwendung einer analytischen Zentrifuge (nachfolgend als „Adhesion Analyser LUMiFrac®“ bezeichnet). Zu den Festigkeiten, die mit Hilfe des LUMiFrac® unter Verwendung aufgeklebter Prüfstempel bestimmt werden, gehören die Fügefestigkeit (FF) von Klebverbindungen, die Haftfestigkeit (HF) von Beschichtungen sowie die Verbundfestigkeit (VF) von Faserverbundwerkstoffen. Aufbauend auf zwei Funktionsmustern der analytischen Zentrifuge sollen für die genannten Anwendungsszenarien (FF, HF, VF) in Anlehnung an die geltenden Normen DIN EN 15870 „Klebstoffe – Zugprüfung zur Bestimmung der Zugfestigkeit von Stumpfklebungen“ und DIN EN ISO 4624 „Beschichtungsstoffe – Abreißversuch zur Beurteilung der Haftfestigkeit“ geeignete Prüfstrategien und -abläufe sowie zum Klebprozess kompatible Aufnahmen für den Prüfkörperverbund in der Zentrifuge entwickelt werden.
Im Ergebnis des Vorhabens soll ein automatisiertes und validiertes Mehr-Proben-Prüfverfahren zur Qualitätssicherung von Verbundfestigkeiten zur Verfügung stehen, welches neben der Hardware auch eine Software für die angepassten Prüfstrategien in Form von SOPs (standard operating procedures) bereitstellt.
Flame projectors for shof effects-Investigations of thermal radiation for assessing safety distances
(2015)
The use of flames as part of shows is state of the art. Besides pyrotechnic flame projectors, the use of projectors that produce flames by burning various gases, liquids and dusts is significantly increasing. In this study infrared radiation in the wavelength range from 7.5 to 14 microns was measured for several systems (flame projectors) and set in relation to known human pain threshold levels. From this relation safety distances been determined for a static scenario (audience watching show) and compared with those of approved pyrotechnic articles.
Die Verwendung von Flammen im Rahmen von Shows ist heute Stand der Technik. Neben pyrotechnischen Flammenprojektoren kommen zunehmend Anlagen zum Einsatz, die Flammen durch die Verbrennung von Gasen, Flüssigkeiten und Stäube erzeugen.
Es wurde die Infrarotstrahlung im Wellenlängenbereich von 7,5 – 14 µm der verschiedenen Systeme (Flammenprojektoren) gemessen und in Relation zu bekannten Grenzwerten für die gesundheitliche Schädigung von Personen gesetzt. Aus dieser Relation sind dann Schutzabstände für ein statisches Szenario (Publikum verfolgt Show) bestimmt worden.
Combining CO2 Streams from Different Emitters – A Challenge For Transport And Storage Infrastructure
(2015)
The European Directive 2009/31/EC on the geological storage of CO2 envisages an open access of CO2 streams from different emitters to a nation- or even EUwide CO2 pipeline network if CO2 stream compositions meet “reasonable minimum composition thresholds”. As of today it is not known how such “composition thresholds” may be defined and which impurity levels may be viable in practical application.
To set up recommendations for criteria and respective threshold values for CO2 stream compositions, the project “CLUSTER” will investigate how a dynamic interplay – both in terms of mass fluxes and compositions – of CO2 streams from regionally clustered CO2 sources sharing a transport and storage infrastructure will impact corrosion, e.g., of pipelines and plant components, and geochemical alteration of cap rocks and reservoir rocks. In addition, the behaviour of such a highly dynamic CCS system will be considered for an overall optimization of system design including CO2 stream mixing schemes and facilities or interim CO2 storage.
Due to the large quantities of construction and demolition waste (CDW) in Europe, its reuse or recycling is of particular importance. Although several countries already recycle high amounts of CDW, the use as secondary raw materials is often limited by inferior building material properties. Specific characteristics, like high porosity and low density are caused by hardened cement paste in crushed concrete and the content of mortar and plaster in brick debris. Impurities like wood or gypsum and also harmful substances like organic pollutants may be a major problem for a reuse and should be minimized. Therefore unwanted materials and impairing substances have to be separated from the secondary building material stream. This can be done during the demolition process by using techniques for selective dismantling or during the subsequent treatment of the resulting rubble. Since almost all processing steps are associated with environmental impacts, the benefits of saving natural resources by applying secondary building materials should be weighed carefully. An environmental performance evaluation was undertaken to assess different techniques for reducing gypsum in recycled concrete aggregates, aiming at a minimization of elutable sulfates. These results were compared to the environmental impacts of the extraction of natural aggregates for concrete.
In this work an approach for smoothing the oscillations of normal contact is presented. On the other side a higher order time discretization scheme in association with a higher order spatial discretization, like the spectral element method, is used. The contact constraints are reformulated in order to get an explicit equation for the motion.
In this work an approach for smoothing the oscillations of normal impact is presented. In addition, a higher order time discretization scheme in association with a higher order spatial discretization, like the spectral element method, is investigated regarding its convergence rates.
The qualitative and quantitative investigations of historical iron-gall inks by use of μ-XRF spectrometry is a common method for analyzing the diff erences in their composition. When a fingerprint is established, it is possible to characterize the distinguishable inks used in the production of medieval manuscripts, and, in turn assist in the reconstruction of the manuscript’s history.The characterization of the primary inks in palimpsests, i.e. manuscripts written on re-used parchment, presents a serious problem as the effect of the partial removal on the inks fi ngerprint is yet known.
In this paper we explore our preliminary results concerning the effects of two removal techniques on the fingerprint of iron-gall inks on parchment.
This project aims to develop capacity to produce certified reference materials (CRMs) for environmental analysis by transferring know-how between the partners and combining their skills to focus on environmental CRM production. The production process includes good manufacturing practices for processing materials, method development, the validation and application of homogeneity, stability and characterisation tests, the calculation of individual uncertainties (between-unit inhomogeneity, long term stability, characterisation) and combination of uncertainties to determine overall uncertainty of the matrix reference materials. An inter laboratory comparison registered as a EURAMET project is set as the ultimate project outcome, confirming the partners’ capabilities in applying newly acquired skills.
This project aims to develop capacity to produce certified reference materials (CRMs) for environmental analysis by transferring know-how between the partners and combining their skills to focus on environmental CRM production. The production process includes good manufacturing practices for processing materials, method development, the validation and application of homogeneity, stability and characterisation tests, the calculation of individual uncertainties (between-unit inhomogeneity, long term stability, characterisation) and combination of uncertainties to determine overall uncertainty of the matrix reference materials. An inter laboratory comparison registered as a EURAMET project is set as the ultimate project outcome, confirming the partners’ capabilities in applying newly acquired skills.
The importance of microRNA (miRNA) dysregulation for the development and progression of diseases and the discovery of stable miRNAs in peripheral blood have made these short-sequence nucleic acids next-generation biomarkers. Here we present a fully homogeneous multiplexed miRNA FRET assay that combines careful biophotonic design with various RNA hybridization and ligation steps. The single-step, single-temperature, and amplification-free assay provides a unique combination of performance parameters compared to state-of-the-art miRNA detection technologies. Precise multiplexed quantification of miRNA-20a, -20b, and -21 at concentrations between 0.05 and 0.5 nm in a single 150 mL sample and detection limits between 0.2 and 0.9 nm in 7.5 mL serum samples demonstrate the feasibility of both highthroughput and point-of-care clinical diagnostics.
One of the most important collections of manuscripts and wall paintings from sites of the northern Silk Road, discovered at the beginning of the 20thC, are deposited in Berlin. The fragments represent a broad spectrum of scripts, languages, and painting styles depending on the region of origin and purpose of dissemination. The manufacturing material reflects the various influences in the oasis sites. Based on analyses of some pigments, examples are posed.
Das Laser-MSG-Hybridschweißverfahren führt bei untersuchten hochfesten Pipelinestählen API X80 und X120 reproduzierbar zu Schweißverbindungen mit anforderungsgerechten Zähigkeitseigenschaften.
Eine metallurgische Beeinflussung der Schweißnahtzähigkeit ist durch eine gezielte Auswahl des Zusatzwerkstoffes möglich, wobei die maximale Eindringtiefe des Zusatzwerkstoffes in die Tiefe der Laserhybridnaht zu beachten ist.
Die maximal erzielbare Eindringtiefe des Zusatzwerkstoffes ist auf ca. 14 mm begrenzt. Die eingesetzte Art des MSG-Lichtbogens hatte keinen erkennbaren Einfluss auf die Aufmischung im Laseranteil der Laserhybridnaht.
Die besseren Ergebnisse der Kerbschlagzähigkeit konnten mit Metallpulverdrähten erreicht werden.
Mit den erzielten gemittelten Werten der Schlagarbeit: ca. 200 J bei -60°C für X80 und ca. 53 J bei -40°C für X120 werden Anforderungen der Norm API 5L und DIN EN 10208-2 für die beiden untersuchten Grundwerkstoffe erfüllt.
Sixteen Ayyubid-Mamluk glazed pottery sherds were analyzed in order to identify and characterize the elemental composition to determine their provenance. The tested sherds were collected from the historical site of Karak Castle, southern Jordan.
Chemical analysis for the sixteen samples has been carried out using Synchrotron Radiation X-ray Fluorescence Spectrometry (SR-XRF) Technique. Furthermore, the semiquantitative analysis of the elements Fe – Cu – Zn – Br – Rb – Sr – Y – Zr – Nb – Mo – Pd – Ag – Cd and Pb has been performed for the samples based on Principal Component Analysis (PCA) and hierarchical Cluster Analysis with Bray-Curtis in order to define grouping of different glazed pottery by obtaining information on their similarity and clustering. The results of chemical analysis provided persuasive evidence that the Karak Castle pottery sherds have at least three different sources of provenance.
The modeling of waveguides by means of the Scaled Boundary Finite Element Method (SBFEM) has recently been addressed and is considered an effective procedure for the simulation of ultrasonic guided waves in plates and uniform structures, as well as their interaction with defects. This work presents the extension of the known applications like uniform concrete foundation cylinders to structures with more complex shapes and defects. The main focus is the required modeling of 3-D structures in SBFEM to solve these efficiently. Furthermore the coupling of different models is discussed. This involves models like a mainly uniform foundation cylinder with varying material behavior or geometry in certain areas which has to be modeled in 3-D SBFEM. With the presentation of numerical examples the accuracy and performance of the modeling is discussed and the advantages in improving numerical stability are shown.
Untergrundspeicher für Roh- und Abfallstoffe gewinnen zunehmend an Bedeutung. Verwendet werden sie vor allem für Stoffe wie Erdgas, Wasserstoff, Erdöl und neuerdings auch für Kohlen-stoffdioxid (CO2). Diese Stoffe werden meist unter Druck in Kavernen- oder Porenspeichern einge-lagert. Die Speicher dienen einerseits zum Ausgleich von Ungleichgewichten zwischen Ange-bot/Förderung und Nachfrage/Verbrauch und zur Erhöhung der Versorgungssicherheit. Anderer-seits bestehen Konzepte Abfallstoffe oder Gefahrstoffe für die Umwelt (aktuell CO2-Speicherung) dort für lange Zeiträume einzulagern. Mit den Einlagerungsstoffen verbunden ist ein signifikantes Gefahrenpotential für Mensch und Umwelt, falls es trotz aller Sicherheitsmaßnahmen zu einem unkontrollierten Austritt dieser Stoffe kommen sollte. Daher kommt dem Monitoring derartiger Untergrundspeicher und den darüber befindlichen Bodenstrukturen eine extrem hohe Bedeutung zu.
Ein hochaktuelles Beispiel, das die Überwachung entsprechender Bodenflächen fordert, ist die unterirdische CO2-Speicherung im Rahmen der CO2-Abscheidung und -Speicherung (Carbon Dioxide Capture and Storage, CCS). CCS gilt als wichtige Brückentechnologie der Energiewirtschaft und wird weltweit vorangetrieben, während die Sicherheit von Bevölkerung und Biosphäre noch kont-rovers diskutiert wird. Auch die EU setzt auf CCS und gibt in der EU-Richtlinie 2009/31 als Ziel-setzung bis 2015 vor, 15 Pilotanlagen zu bauen und in Betrieb zu nehmen. Als Bedingung für die Genehmigung der CO2-Speicherung ist explizit die Überwachung der Speicheranlagen durch Monito-ring vorgeschrieben, wobei die technisch besten Lösungen zum Einsatz kommen sollen.
Das zu entwickelnde Messsystem adressiert neben den o.g. Anwendungsfeldern weitere, bei denen insbesondere die Emission von Gasen ein Risiko für Mensch und Umwelt darstellt oder wirt-schaftlichen Schaden verursachen kann. Hierzu zählen die Überwachung von Abfalldeponien, Ge-fahrgutlagerstätten, kontaminierten Altlastengebieten, Moor-, Torf-, Kohleflözen (präventive Branderkennung) und geodynamisch aktiven Regionen. Auch moderne Fördertechnologien, wie das Hot-Dry-Rock-Verfahren (HDR) zur Energiegewinnung durch Einpressen von überkritischem CO2 in den Erdkörper, das die Beweglichkeit eines Gases mit der Dichte einer Flüssigkeit kombiniert und Wärmeaustausch im Erdinneren bewirkt, bergen das Risiko unkontrollierter Gasemissionen und bedürfen der umfassenden Überwachung.
Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimuli-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimuli-responsive surfaces may help integrating synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. For the first time, rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects.
Oxidation of a Fe-13Cr alloy under water vapor at 600 °C produced a zone of nano-sized precipitation underneath the outside scale formed by iron oxides and Fe‒Cr spinel. The majority of the spinel layer shows a mixed orientation relationship to the ferritic matrix {100}α || {100}sp & <011>α || <001>sp. However, also the discovered precipitated particles are characterized by the same crystallographic orientation relationship to the respective ferritic parent grain. The habit of the precipitates is best described by a lath morphology with their main axis parallel to <100> of ferrite.
Energy dispersive X-ray spectroscopy (EDX) and electron backscatter diffraction (EBSD) in an scanning electron microscope (SEM) have been applied to characterize the oxide layer in the micrometer scale. The clearly smaller precipitates were subsequently investigated by transmission electron microscopy (TEM). Specimens have been prepared by focused ion-beam (FIB) milling at an area previously characterized by EBSD. They cover the ferritic base material, but mainly the precipitation zone and the Fe‒Cr spinel layer. Energy filtered selected area diffraction (SAD) in the conventional (C)TEM and high-angle annular darkfield (HAADF) imaging in the scanning (S)TEM mode were employed in the characterization of the specimens.
Der Fänger im Spülgas
(2015)
Supplementary cementitious materials (SCMs) are largely used all over the world. The leading SCMs are fly ash (FA) and slag. However, such materials originate from industries that are not well established in sub-Saharan Africa (SSA). Therefore, it becomes extremely challenging and expensive to build up sustainable cement and concrete. For SSA, agriculture is one of the leading economic sectors. Agricultural by-products such as rice husk ash (RHA), can be a potential binder material beneficial for use in a cementitious system. RHA combined with limestone filler (LSF) is an option that can be practised for rice producing countries in Africa.
The presentation gives an overview about mechanical and thermal testing of packages and containers for radioactive material in Germany. The test facilities of BAM and the main measurement methods are described followed by testing of containers (prototype, full-scale, reduced scale) as well as components and specimens.
Structuring of LTCC substrates by a combination of pressure-assisted sintering and hot-embossing
(2015)
A novel technology for the structuring of LTCC surfaces is introduced. The material is shaped in a zero-shrinkage process by embossing a glassy carbon mold into the softened LTCC directly after termination of the shrinkage. Three commercially available LTCC compositions (Ceramtape GC, Heratape CT707, and DP951) were tested. Diverse raised and lowered structures including rings, grids, and characters were fabricated. Different material behavior was observed for the tested compositions. Promising results were achieved with Ceramtape GC. Embossing of precise, 40 µm deep circular cavities and 50 µm high raised characters is demonstrated. Processing of 100 × 100 mm² substrates is possible. DP951 showed very good moldability, but also unwanted material displacement due to evaporating lead. A high displacement capacity but uneven heights of embossed structures were observed on CT707 samples. SEM investigations proved the precise transfer of surface contours from the mold to the LTCC. Thereby, the high potential of the hot-embossing process for micro-patterning of LTCC is illustrated.
Two types of surface modified magnetite (Fe3O4) nanoparticles, coated with either tannic acid (TA) or dissolved natural organic matter (NOM), were evaluated as magnetic heterogeneous catalysts. Simple and efficient procedures for the synthesis of the magnetic catalysts were employed, their properties being fully assessed by various characterization techniques. The catalytic activity in heterogeneous oxidation of aqueous solutions containing Bisphenol A (BPA) over the catalysts was comparatively studied. The optimum experimental parameters were: 1g/L of catalysts, 10 mM H2O2, under UV irradiation. The highest mineralization rates were observed for Fe3O4-TA catalyst. More than 80% of BPA were removed after 30 minutes of reaction time under the specified experimental conditions. The results showed that the obtained catalysts are suitable candidates for the removal of pollutants in wastewaters by means of heterogeneous reaction
Green Fenton-like magnetic nanocatalysts: Synthesis, characterization and catalytic application
(2015)
Five iron oxalate core–shell magnetite nanoparticles catalysts are evaluated as magnetic heterogeneous materials. Simple and efficient procedures for the preparation of magnetic iron oxalate coated nanoparticles are presented. The catalysts are fully characterized using various investigation techniques. Additionally, the formation of photo-sensitized oxygen by spin-trapping using electron spin resonance is investigated. The catalytic activity of two model substrates (carbamazepine and bisphenol A) is also evaluated. The effect of operational parameters (catalyst and H2O2 concentration, UVA light) on the degradation performance of the oxidation process is investigated. The obtained reaction rates depend on the nature of the compound and increase with iron oxide shell thickness of the catalyst. Moreover, these materials show a significant activity during two consecutive tests. The optimum experimental parameters are found to be 1.0 g L−1 of catalysts, 10 mM H2O2, under UVA irradiation. More than 99% of both substrates are removed after 30 min of reaction time under the experimental conditions given above. The results obtained show that the catalysts are suitable candidates for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction.
The concreting of prefabricated concrete structures can lead to insufficient bonding or even to remaining cavities. Honeycombs (aggregate clusters without cement) represent potential weakening of the structure and need to be detected non-destructively. In our study we tested the capability of ground penetrating radar (GPR) techniques for this purpose. We applied GPR in reflection mode and zero-offset profiling (ZOP) transmission mode on a precast concrete twin wall with built-in honeycombs. GPR measurements were performed as two channel measurement with ground coupled antennas with centre frequencies of 1.5 GHz and 2.6 GHz mounted to an automated scanner system.
Our findings show that ZOP transmission measurements are a more efficient method to detect voids in reinforced concrete structures compared to reflection mode measurements. This holds for both the effort needed for the measurement and the evaluation as well as the validity of the data. Honeycombs (basically representing voids) are usually characterized by strongly reduced amplitudes and earlier arrivals of the transmitted wave.
The concreting of prefabricated concrete structures can lead to insufficient bonding or even to remaining cavities. Honeycombs (aggregate clusters without cement) represent potential weakening of the structure and need to be detected non-destructively. In our study we tested the capability of ground penetrating radar (GPR)techniques for this purpose. We applied GPR in reflection mode and zero-offset profiling (ZOP) Transmission mode on a precast concrete twin wall with built-in honeycombs. GPR measurements were performed as twochannel measurement with ground coupled antennas with centre frequencies of 1.5 GHz and 2.6 GHz mounted to an automated scanner system.
Our findings show that ZOP transmission measurements are a more efficient method to detect voids in reinforced concrete structures compared to reflection mode measurements. This holds for both the effort needed for the measurement and the evaluation as well as the validity of the data. Honeycombs (basically representing voids) are usually characterized by strongly reduced amplitudes and earlier arrivals of the transmitted wave.
Amplitudes variation of GPR rebar reflection due to the influence of concrete aggregate scattering
(2015)
Dense GPR measurements of rebar reflection amplitudes Show relative variations, which can be in the order of more than 10% - 20%. Former investigations demonstrated that these variations are caused by the heterogeneity of concrete, i.e. due to the inclusion of aggregates in concrete. These amplitude variations make it difficult to analyse single reflection amplitudes in order to determine the rebar diameter or to estimate the concrete deterioration state. In a systematic study we have quantified the statistical variation of the rebar reflection amplitude for concrete covers of 6 cm, 9 cm, 12 cm, 15 cm and 18 cm, for two different grading curves and for the rebar diameters 12 mm and 28 mm. Also the influence of the wavelength has been investigated by using antennas with different centre frequencies in relation to the aggregate size. The results are discussed with regard to a quantitative amplitude evaluation of GPR measurements and also the potential of using these variations for a characterization of concrete material properties.
Abfallgebinde, die im Endlager Konrad eingelagert werden sollen, müssen die Anforderungen und Kriterien erfüllen, die in den Endlagerungsbedingungen (SE-IB-29/08-Rev-1) und in der Produktkontrolle (SE-IB-30/08-Rev-1) festgelegt sind. Die Qualifizierung der Abfallbehälter erfolgt auf dieser Grundlage in Form von Bauartprüfungen, die von der Bundesanstalt für Materialforschung und -prüfung (BAM) im Auftrag des Bundesamtes für Strahlen-schutz (BfS) durchgeführt werden. Darüber hinaus sind die im Hinblick auf Behälterbauartprüfungen relevanten Nebenbestimmungen aus dem Planfeststellungsbeschluss für das Endlager Konrad zu berücksichtigen. Zur besseren Anwendbarkeit werden diese Nebenbestimmungen in die Endlagerungsbedingungen und die Pro-duktkontrolle eingearbeitet. Begleitend ist als Hilfestellung für die Abfallablieferer und Behälterhersteller ein Leit-faden geplant, der praktikable Nachweisstrategien aufzeigt und, soweit erforderlich, Hintergrundinformationen zu den Spezifikationen der Regelwerke liefert. Die BAM ist vom BfS beauftragt, hierfür Vorschläge zu entwickeln und Empfehlungen abzugeben.
Gravimetrically prepared mono-elemental reference solutions having a well-known mass fraction of approximately 1 g/kg define the very basis of virtually all measurements in inorganic analysis. Serving as the starting materials of all standard/calibration solutions, they link virtually all measurements of inorganic analytes to the purity of the solid materials they were prepared from. In case these solid materials are characterized comprehensively with respect to their purity, this link also establishes direct metrological traceability to The International System of Unit. Within the framework of the European Metrology Research Programme (EMRP), in the Joint Research Project called SIB09 Primary standards for challenging elements, a reference solution of molybdenum was prepared directly from the respective metal with a relative expanded uncertainty associated with the mass fraction of Urel(w) < 0.05 %. A highly accurate and precise ICP OES and MC-ICP-MS method was developed to assist with the preparation and as a dissemination tool.
Most railway embankments in the UK were built in the Victorian era and are of end-tipped construction using materials (usually cohesive) excavated from adjacent cuttings, resulting in a clod-and-matrix structure. Historically, there has been a lack in understanding of the mechanical behaviour of such railway embankments. In the next decade railway traffic in the UK, particularly freight, is forecast to grow considerably. Consequently, there is a need to improve the understanding of how increases in rail traffic loading may influence the mechanical behaviour of railway embankments and thus track performance. The Rail Safety and Standards Board in conjunction with Network Rail is currently undertaking a programme of applied research into this topic. As part of these studies a programme of physical model tests has been carried out. Physical model tests can provide high quality data on system performance under a large range of loading conditions and geometrical configurations. The data can be generated rapidly, with test periods of weeks or months rather than years or decades. Additionally, boundary conditions are well-defined and controlled, compared with the complex situations encountered in full scale embankments in the field. This paper summarises the physical model test programme, the development of the test set-up, the tests themselves and the conclusions drawn.
This paper deals with the system identification of a mechanical structure supported by nonlinear springs subjected to an external load. If all mechanical parameters of the system were known, the displacement of the system subjected to this load could be easily calculated. However, the monitoring applications often deal with the inverse problem. The loads and displacements of the system are known and certain mechanical Parameters of the system are sought. The solution of such inverse problems can be difficult, especially when they have a nonlinear and multimodal character, which often makes them appear intractable at first sight. However, evolutionary computing can be applied to solve this inverse, nonlinear and multimodal problem. Sometimes a prior knowledge exists on certain system properties, which is difficult to implement into analytical or numerical solvers. This knowledge can play a decisive role in identifying the System properties and it can be easily included as a boundary condition when applying evolutionary algorithms.
This article discusses how and under what conditions the unknown spring resistances can be identified. The practical application of this procedure is exemplified here with the mechanical system of a pile foundation.
X-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment ofatoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted andbroadened due to thermal atom motion and by interchain interactions. We present a combined quantummechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol(PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. Inour study, molecular dynamics at finite temperature were performed with a classical forcefield and by abinitio MD (AIMD) using the Car–Parrinello method. Snapshots along the trajectories represent possibleconformers and/or neighbouring environments, with different C1s ionization potentials for individualC atoms leading to broadened XPS peaks. The latter are determined by Δ-Kohn Sham calculations. Wealso examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containingpolymers to the C1s signal of polyethylene. We find that (i) the experimental XPS (C1s) spectra of PVA (position and width) can be roughly repre-sented by single-strand models, (ii) interchain interactions lead to red-shifts of the XPS peaks by about0.6 eV, and (iii) AIMD simulations match the findings from classical MD semi-quantitatively. Further, (iv)the gauging procedure of XPS (C1s) signals to the values of PE, introduces errors of about 0.5 eV.
Ziel des Projektes war, mit Hilfe von Computersimulationen die Brennfleckgröße, das Spektrum und die erreichbare Dosisleistung von Transmissionsröhren vorherzusagen sowie diese Kenngrößen zu optimieren. Hierbei sollten insbesondere die Materialien und Schichtdicken von Substrat und strahlungserzeugender Schicht untersucht werden. Eine Voraussetzung für die Überprüfung der Ergebnisse ist die reproduzierbare, korrekte messtechnische Erfassung von Brennfleckgrößen unterhalb 5 μm.
The damage process of short glass fibre (30% weight) reinforced polyamide caused by mechanical loading was investigated from the beginning on micro cracking level to the incipient crack of mm-dimension. Based on high resolution computer tomography and the X-ray-refraction technique the inner surface due to micro-cracking at the short fibre ends and the fibre matrix debonding of the skin surface of the filament was determined quantitatively. With the knowledge of the fatigue crack propagation rate and fracture toughness of the material from former research projects, it was derived that the total inner surface due to micro cracks measured by X-ray refraction is much higher than the specimen could have withstand the load, supposed the surface is in a localized crack. Hence, the damage process could be described from micro to macro level. Accompanying fractographic investigations endorse the modelling based on the NDT-techniques.
Fatigue life evaluation of spar cap materials by four point bending test on width-tapered specimensa
(2015)
The presented research project focuses on an effective method to evaluate the fatigue strength of thick unidirectional laminates to be applied in spar caps. Therefore, a width-tapered bending specimen was developed for a four point loading set up. Static and fatigue loading was performed with the load ratio of R=-1. The complex stress state was investigated numerically with a finite element analysis. Finally, the concept was proven experimentally on specimens made of pultruded fibre rods. The fatigue behaviour of continuous tapered width by water jet cutting was compared to discrete tapering by rod-drop.
Simple models describing the relationship between basic mechanical properties and the relative density of various types of porous metals (such as foams, sponges and lattice structures) are well established. Carefully evaluating these relationships experimentally is challenging, however, because of the stochastic structure of foams and the fact that it is difficult to systematically isolate density changes from variations in other factors, such as pore size and pore distribution. Here a new method for producing systematic sets of stochastic foams is employed based on electron beam melting (EBM) additive manufacturing (AM). To create idealised structures, structural blueprints were reverse-engineered by inverting X-ray computed tomographs of a randomly packed bed of glass beads. This three-dimensional structure was then modified by computer to create five foams of different relative density ρr, but otherwise consistent structure. Yield strength and Young’s modulus have been evaluated in compression tests and compared to existing models for foams. A power of 3 rather than a squared dependence of stiffness on relative density is found, which agrees with a recent model derived for replicated foams. A similar power of 3 relation was found for yield strength. Further analysis of the strength of nominally fully dense rods of different diameters built by EBM AM suggest that surface defects mean that the minimum size of features that can be created by EBM with similar strengths to machined samples is ∼1 mm.
This paper deals with the initiation and propagation of corrosion in mortar specimens precracked under mechanical loading and carbonated in climate accelerated conditions (50 % CO2–65 % RH)for 15–23 weeks. Mechanical loading led to transverse macro-cracks and damage at the steel-mortar interface characterized by micro-cracks (cover controlled cracking) which favour the carbonation of crack walls and the interface with the steel bar. Wetting–drying cycles performed after carbonation favoured corrosion initiation all along the steel bar because of the carbonated interface and corrosion propagation because of the creation of corrosion cracks which appear to develop from the micro-cracks induced by the mechanical load. Results also show that rust develops all around the perimeter of the carbonated steel bar but that the corrosion layer is thicker in the lower half surface of the reinforcement than that observed in the upper half. Results indicate that the distribution and composition of corrosion products depend on the thickness of the rust layer and that the multilayered structure of rust depends mainly on its thickness.
Transport packages for spent nuclear fuel have to be assessed with respect to specific transport conditions which are defined in the safety regulations of the International Atomic Energy Agency. In general, gastight fuel rods constitute the first barrier of the containment system. The physical state of the spent fuel and the fuel rod cladding as well as the geometric configuration of the fuel assemblies are important inputs for the evaluation of the package safety under transport conditions. The objective of this paper is to discuss the methodologies accepted by BAM for the authority assessment of spent fuel behavior within the package design approval procedure of German package designs. In particular, cracks or failures in the fuel rod cladding can occur under regulatory transport conditions. These defects can cause the release of gas, volatiles, fuel particles or fragments into the package cavity and have to be considered properly in the safety analysis. Another issue is the transport of defective fuel rods. One concept is to use special canisters which can be handled like fuel assemblies. This concept requires additional assessment concerning drying, sealing and the mechanical and thermal design of such canisters. The package as a mechanical system is characterized by a complex set of interactions, e.g. between the fuel rods within the assembly as well as between the fuel assemblies, the basket, and the cask containment. This complexity together with the limited knowledge about the material properties and the variation of the fuel assemblies regarding cladding material, burn-up and the operation history makes an exact mechanical analysis of the fuel rods nearly impossible. The simplified approaches to consider conservatively spent fuel behavior currently accepted by BAM are presented here.