196 research outputs found
The circulation and consumption of Red Lustrous Wheelmade Ware: petrographic, chemical and residue analysis
yesRed Lustrous Wheelmade ware is one of the most recognisable classes of pottery from the Late Bronze Age of the east Mediterranean. Yet both its production source and the nature of its contents and use remain a source of some debate. These questions are tackled here through an intensive programme of scientific analysis involving 95 samples of Red Lustrous Wheelmade ware and related wares from seven sites in Turkey, Cyprus and Egypt. Petrography and instrumental neutron activation analysis are combined in the study of the ceramic fabrics, with a view to specifying the source of this ware; while gas chromatography and gas chromatography-mass spectrometry are used to analyse absorbed and visible residues in and on the sherd samples, in the hope of shedding light on vessel contents and possible use. The results of the fabric
analysis show the ware to be extremely homogeneous, indicative of a single source: northern Cyprus is at present the most likely candidate, although further analysis, particularly of clay samples from the region in question, would certainly be desirable. The residue analysis suggests that Red Lustrous Wheelmade ware might have been used to carry some kind of plant oils, possibly perfumed, and that in some instances the vessel interior was coated with beeswax as a sealant.AHR
In situ root identification through blade penetrometer testing – Part 2:field testing
The spatial distribution, depths and diameters of roots in soil are difficult to quantify but important to know when reinforcement of a rooted slope or the stability of a plant is to be assessed. Previous work has shown that roots can be detected from the depth–resistance trace measured using a penetrometer with an adapted blade-shaped tip. Theoretical models exist to predict both forces and root displacements associated with root failure in either bending or tension. However, these studies were performed in dry sand under laboratory conditions, using acrylonitrile butadiene styrene root analogues rather than real roots. In this paper blade penetrometer field testing on two forested field sites, with Sitka spruce and pedunculate oak in sandy silt and clayey silt, respectively, is used to evaluate models under field conditions. Root breakages could be detected from blade penetrometer depth–resistance traces and using complementary acoustic measurements. Predictions of additional penetrometer resistance at root failure were more accurate than the displacement predictions. An analytical cable model, assuming roots are flexible and fail in tension, provided the best predictions for Sitka roots, whereas thick oak roots were better predicted assuming bending failure. These matched the modes of failure observed in three-point bending tests of the root material in each case. The presence of significant amounts of gravel made it sometimes difficult to distinguish between hitting a root or a stone. The root diameter could be predicted when root strength and stiffness, and soil penetrometer resistance were known and the right interpretative model was selected. Estimates based on peak force were more accurate than those based on root displacement. This measurement procedure is therefore a potentially valuable tool to quantify the spatial distribution of roots and their reinforcement potential in the field. </jats:p
Evaluation of X-ray/EUV Nanolithography Facility at AS Through Wavefront Propagation Simulations
Synchrotron light sources can provide the required spatial coherence,
stability and control that is required to support the development of advanced
lithography at the extreme ultraviolet and soft X-ray wavelengths that are
relevant to current and future fabricating technologies. Here we present an
evaluation of the optical performance of the soft X-ray (SXR) beamline of the
Australian Synchrotron (AS) and its suitability for developing interference
lithography using radiation in the 91.8 eV (13.5 nm) to 300 eV (4.13 nm) range.
A comprehensive physical optics model of the APPLE-II undulator source and SXR
beamline was constructed to simulate the properties of the illumination at the
proposed location of a photomask, as a function of photon energy, collimation,
and monochromator parameters. The model is validated using a combination of
experimental measurements of the photon intensity distribution of the undulator
harmonics. We show that the undulator harmonics intensity ratio can be
accurately measured using an imaging detector and controlled using beamline
optics. Finally, we evaluate photomask geometric constraints and achievable
performance for the limiting case of fully spatially coherent illumination.Comment: 21 pages, 7 figures, 3 tables. Preprint: submitted to Journal of
Synchrotron Radiation 16/11/2
Comparison of new <i>in situ </i>root-reinforcement measuring devices to existing techniques
Mechanical root-reinforcement is difficult to quantify. Existing in-situ methods are cumbersome, while modelling requires parameters which are difficult to acquire. In this paper, two new in-situ measurement devices are introduced ('cork screw' and 'pin vane') and their performance is compared to field vane and laboratory direct shear strength measurements in fallow and rooted soil. Both new methods show a close correlation with field vane readings in fallow soil. Tests in reinforced soil show that both new methods can be installed without significant root disturbance. The simplicity of both new methods allows for practical in-situ use and both can be used to study soil stress-strain behaviour, thus addressing some major limitations in existing methodologies for characterising rooted soil.</p
Effect of root spacing on interpretation of blade penetration tests-full-scale physical modelling
The spatial distribution of plant roots is an important parameter when the stability of vegetated slopes is to be assessed. Previous studies in both laboratory and field conditions have shown that a penetrometer adapted with a blade-shaped tip can be used to detect roots from sudden drops in penetrometer resistance. Such drops can be related to root properties including diameter, stiffness and strength using simpleWinkler foundation models, thereby providing a field instrument for rapid quantification of root properties and distribution. While this approach has proved useful for measuring single widely-spaced roots, it has not previously been determined how the penetrometer response changes as a result of roots being in close proximity. Therefore in this study 1-g physical modelling (at 1:1 scale) was conducted to study the effect of vertical root spacing using horizontal, straight 3D-printed root analogues. Results showthatwhen roots are closely spaced, there is significant interaction between them, resulting in higher apparent root displacements to failure and an increased amount of energy being dissipated. This preliminary work shows that the interpretive models used to analyse the penetrometer trace require further development to account for root-soil-root interactions in densely rooted soil.</p
In situ root identification through blade penetrometer testing – Part 1:interpretative models and laboratory testing
Root architecture and reinforcement are important parameters to measure the safety of vegetated slopes and stream banks against slope instability and erosion or to assess the stability of plants against environmental loading (e.g. windthrow of trees). However, these are difficult to measure without time-consuming sampling or counting procedures. Previous studies proposed using a penetrometer with an adapted geometry, and showed that individual root breakages could be detected as sudden drops in penetrometer resistance. However, there are no existing models to derive root properties from the measured traces. Here, several interpretative models are developed and their performance at identifying and characterising buried acrylonitrile butadiene styrene root analogues of varying diameter and architecture in sand are assessed. It was found that models, assuming the analogues broke in bending rather than tension, provided good predictions for the force–displacement behaviour. The simple analytical bending model developed here was shown to perform almost as well as more sophisticated numerical models. For all models, the predictions of additional penetrometer force required to break the root analogue were more accurate than predictions for lateral root displacement required to reach failure. The root analogue diameter and to a lesser extent the soil resistance and root angle were shown to affect the penetrometer resistance strongly. Root branching, root length and the distance between the point of load application and a root boundary (root tip or parent root) had a much smaller effect. When the root failure mechanism, root strength, root stiffness and soil resistance are known, an accurate prediction of the root diameter can be made based on the root peak resistance value identified from a blade penetration test. Penetrometer testing, a test which is easy to perform in the field, coupled with an accurate interpretative model might therefore be an effective method to rapidly quantify the spatial distribution, depths and diameters of roots. </jats:p
A Macroelement Approach for the Stability Assessment of Trees
Interaction diagrams in the generalized 3D loading space of vertical (V), horizontal (H) and moment (M) actions constitute the basis of the design of foundation structures in case of complex loads combinations. The mechanical response of such systems is frequently interpreted in terms of the ‘macroelement’ theory, where a generalized incremental constitutive relationship is introduced, linking the displacements and rotations of the foundation (playing the role of generalized strains) to the histories of applied loading components (i.e. the generalized stresses). In this paper an attempt to extend a classical macroelement framework, to the case of root-soil interaction presented. The model is calibrated on small scale experimental data on 3D printed plastic root systems, subject to combined V-H-M loads, and a parametric analysis on the main governing parameters is discussed. The comparison between numerical and experimental data suggests that the macroelement approach could be an efficient and simple analytical tool for describing the whole moment-rotation curve, overcoming the main simplifying hypotheses currently employed in arboriculture practice
Excavation of Neopalatial deposits at Tholos (Kastri), Kythera
Several rock-cut features, exposed on the surface of a trackway in the Tholos area of Kastri, Kythera, were excavated in July-August 2000 as a synergasia between Kythera Island Project and 2nd Ephoria of Prehistoric and Classical Antiquities. Although the surviving deposits were extremely shallow, they produced large quantities of conical cups and other pottery of Late Minoan I date. Further comparative analysis of the features themselves and their finds suggests that these are the remains of tomb chambers similar to those excavated in the area in the 1960s. These tombs and their assemblages show extremely strong cultural connections with Crete, but also idiosyncrasies that probably reflect the particular mortuary customs of the island. / Abstract in Greek: Τον Ιούιο-Αύγουστο 2000 εράϕορα διάϕορα λαξύματα στον βράχο, ορατά στην επιϕάνεια μονοπτιού στην περιοχἠ Θόλου Καστρίου στα κύθηρα, στο πλαίσιο συνεργασίας μεταξύ του Κρογράμματος για τη νήσο των Κυθήρων και της Βʹ Εϕορείας Προϊστρικών και Κλασικών Αρχαιοτήτων. Αν και οι διασωθείσες επιχώσεις ήταν εξαιρετικἀ, ρηχές, απέδωσαν μεγάλες ποσότες κωνικών κυπέλλων και άλλης κεραμεικής, χρονολογουμένων στην Υστερομινωική Ι. Περαιτέρω ανάλυση των λαξευμάτων καθʹ εαυτών και των ευρημάτων, δείχνει ότι, πρόκειται για υπολείμματα θαλαμωτών τάϕων, παρόμοιων με εκείνους που ανασκάϕηκαν στην περιοχή την δεκαετα του 1960. Οι τάϕοι αυτοι και το περιεχόμενό τους παρουσιάζουν εξαιρετικά άντονες πολιτισικές διασυνδέσεις με την Κρήτη, αλλά επι σης και ιδιομορϕίες οι οποίες πιθανώς αντανακλούνιδιαίτερα ταϕικά άθιμα του νησιού
Lars Hætta’s miniature world: Sámi prison op-art autoethnography
This article examines a collection of miniature objects, now held in museum collections, which were originally made by a Sámi political prisoner in Norway during the mid-19th century as part of an educational programme. The author draws on recent developments in the theory of miniaturization to consider these miniatures as examples of prison op-art autoethnography: communicative devices which seek to address broad and complex social issues through the process of the creation and distribution of semiophorically functionless mimetic objects of reduced scale and complexity, and which reflect the restrictions of incarcerated artistic expression and the questions this raises regarding authenticity and hybridity
An efficient and locking-free material point method for three dimensional analysis with simplex elements
The Material Point Method is a relative newcomer to the world of solid mechanicsmodelling. Its key advantage is the ability to model problems having large defor-mations while being relatively close to standard nite element methods, howeverits use for realistic engineering applications will happen only if the material pointcan be shown to be both ecient and accurate (compared to standard nite elementmethods), when modelling complex geometries with a range of material models. Inthis paper we present developments of the standard material point method aimed atrealising these goals. The key contribution provided here is the development of amaterial point method that avoids volumetric locking (arising from elastic or elasto-plastic material behaviour) whilst using low order tetrahedral nite elements forthe background computational mesh, hence allowing unstructured background gridsto be used for complex geometries. We also show that these developments can beeectively parallelised to improve computational ecienc
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