Home About us Contact
|
Home About us Contact | ||
|
|
||
Observed Features (observed + feature)
Selected AbstractsStructural Health Monitoring via Measured Ritz Vectors Utilizing Artificial Neural NetworksCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2006Heung-Fai Lam Unlike most other pattern recognition methods, an artificial neural network (ANN) technique is employed as a tool for systematically identifying the damage pattern corresponding to an observed feature. An important aspect of using an ANN is its design but this is usually skipped in the literature on ANN-based SHM. The design of an ANN has significant effects on both the training and performance of the ANN. As the multi-layer perceptron ANN model is adopted in this work, ANN design refers to the selection of the number of hidden layers and the number of neurons in each hidden layer. A design method based on a Bayesian probabilistic approach for model selection is proposed. The combination of the pattern recognition method and the Bayesian ANN design method forms a practical SHM methodology. A truss model is employed to demonstrate the proposed methodology. [source] Quantitative analysis of the microscale of auxetic foamsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2005N. Gaspar Abstract The auxetic foams first produced by Lakes have been modelled in a variety of ways, each model trying to reproduce some observed feature of the microscale of the foams. Such features include bent or broken ribs or inverted angles between ribs. These models can reproduce the Poisson's ratio or Poisson's function of auxetic foam if the model parameters are carefully chosen. However these model parameters may not actually reflect the internal structure of the foams. A big problem is that measurement of parameters such as lengths and angles is not straightforward within a 3-d sample. In this work a sample of auxetic foam has been imaged by 3-d X-ray computed tomography. The resulting image is translated to a form that emphasises the geometrical structure of connected ribs. This connected rib data are suitably analysed to describe both the microstructural construction of auxetic foams and the statistical spread of structure, that is, the heterogeneity of an auxetic foam. From the analysis of the microstructure, observations are made about the requirements for microstructural models and comparisons made to previous existing models. From the statistical data, measures of heterogeneity are made that will help with future modelling that includes the heterogeneous aspect of auxetic foams. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Visual modelling: from images to imagesCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 4 2002Marc Pollefeys Abstract This paper contains two parts. In the first part an automatic processing pipeline is presented that analyses an image sequence and automatically extracts camera motion, calibration and scene geometry. The system combines state-of-the-art algorithms developed in computer vision, computer graphics and photogrammetry. The approach consists of two stages. Salient features are extracted and tracked throughout the sequence to compute the camera motion and calibration and the 3D structure of the observed features. Then a dense estimate of the surface geometry of the observed scene is computed using stereo matching. The second part of the paper discusses how this information can be used for visualization. Traditionally, a textured 3D model is constructed from the computed information and used to render new images. Alternatively, it is also possible to avoid the need for an explicit 3D model and to obtain new views directly by combining the appropriate pixels from recorded views. It is interesting to note that even when there is an ambiguity on the reconstructed geometry, correct new images can often still be generated. Copyright © 2002 John Wiley & Sons, Ltd. [source] Analysis and interpretation of flint toolmarks found on bones from West Tump long barrow, GloucestershireINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1 2004M. J. Smith Abstract West Tump is a Neolithic chambered tomb originally excavated in 1880. The mound was found to contain a mixed skeletal assemblage, the majority of which was disarticulated. Between 2000 and 2001 material from the site including human bone was re-examined with a portion of this project focused on taphonomic evidence observed on the human skeletal material. Amongst the factors selected for investigation were deliberate toolmarks. Three specimens were identified as exhibiting toolmarks. Analysis demonstrated that the observed features were cutmarks, consistent with the use of flint tools. However those on two of the specimens were found to be both post-mortem and recent. The cutmarks observed on the remaining specimen, a right clavicle, were identified as having been inflicted during the peri-mortem period and consistent with decapitation. British Neolithic mortuary practice has been the subject of ongoing debate since the earliest excavations of relevant sites, but until very recently few assemblages from such contexts have been re-examined and much of the data in use has derived from sources of considerable age and questionable reliability. The selective removal of specific skeletal elements (particularly skulls) has repeatedly been described in the literature regarding the collective funerary monuments of this period. It has often been assumed that such practices took place after the soft tissues had decayed. One of the examples discussed, suggests this may not always have been the case and the potential significance of this finding is discussed in addition to a possible interpretation of the cutmarks seen on the remaining specimens. Copyright © 2004 John Wiley & Sons, Ltd. [source] Enamel hypoplasia of the primary dentition in a 4-year-old with intestinal lymphangiectasiaINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 5 2005P. ARROW Summary. Intestinal lymphangiectasia (IL) is a rare disorder, and its incidence and prevalence is unknown for either Australia or world-wide. It is characterized by diarrhoea, mild steatorrhoea, oedema, enteric loss of protein (protein-losing enteropathy) and abnormal dilated lymphatic channels in the small intestine. Whilst oedema and diarrhoea are the predominant clinical features, other observed features include hypoalbuminemia, hypogammaglobulinemia, trace metal deficiency, hypocalcemia and chylous pleural effusions. While medical presentation of the condition has been reported widely, few descriptions of oral findings have been published. A search of Medline found two reports of dental findings in the permanent dentition in patients with IL. To date, there have been no reports on dental findings in the primary dentition. The primary dentition of a 4-year-old boy with IL had teeth with enamel defects which reflected the timing of enamel development and the period in which the disease was active. The present report highlights the need for early involvement of the dental team in the dental management of children with IL. [source] Palaeoproterozoic high-pressure granulite overprint of the Archean continental crust: evidence for homogeneous crustal thickening (Man Rise, Ivory Coast)JOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2010P. PITRA Abstract The character of mountain building processes in Palaeoproterozoic times is subject to much debate. Based on the discovery of high-pressure granulites in the Man Rise (Côte d'Ivoire), several authors have argued that Eburnean (Palaeoproterozoic) reworking of the Archean basement was achieved by modern-style thrust-dominated tectonics. A mafic granulite of the Kouibli area (Archean part of the Man Rise, western Ivory Coast) displays a primary assemblage (M1) containing garnet, diopsidic clinopyroxene, red-brown pargasitic amphibole, plagioclase (andesine), rutile, ilmenite and quartz. This assemblage is associated with a subvertical regional foliation. Symplectites that developed at the expense of the M1 assemblage contain orthopyroxene, clinopyroxene, plagioclase (bytownite), green pargasitic amphibole, ilmenite and magnetite (M2). Multiequilibrium thermobarometric calculations and P,T pseudosections calculated with thermocalc suggest granulite facies conditions of , 13 kbar, 850 °C and <7 kbar, 700,800 °C for M1 and M2, respectively. In agreement with the qualitative information obtained from reaction textures and chemical zoning of minerals, this suggests an evolution dominated by decompression accompanied by moderate cooling. A Sm,Nd garnet , whole-rock age of 2.03 Ga determined on this sample indicates that this evolution occurred during the Palaeoproterozoic. It is argued that from the geodynamic point of view the observed features are best explained by homogeneous thickening of the margin of the Archean craton, re-heated and softened due to the accretion of hot, juvenile Palaeoproterozoic crust, as well as coeval intrusion of juvenile magmas. Crustal shortening was mainly accommodated by transpressive shear zones and by lateral crustal spreading rather than large-scale thrust systems. [source] Global lopsided instability in a purely stellar galactic discMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007Kanak Saha ABSTRACT It is shown that pure exponential discs in spiral galaxies are capable of supporting slowly varying discrete global lopsided modes, which can explain the observed features of lopsidedness in the stellar discs. Using linearized fluid dynamical equations with the softened self-gravity and pressure of the perturbation as the collective effect, we derive self-consistently a quadratic eigenvalue equation for the lopsided perturbation in the galactic disc. On solving this, we find that the ground-state mode shows the observed characteristics of the lopsidedness in a galactic disc, namely the fractional Fourier amplitude A1, increases smoothly with the radius. These lopsided patterns precess in the disc with a very slow pattern speed with no preferred sense of precession. We show that the lopsided modes in the stellar disc are long-lived because of a substantial reduction (approximately a factor of 10 compared to the local free precession rate) in the differential precession. The numerical solution of the equations shows that the ground-state lopsided modes are either very slowly precessing stationary normal mode oscillations of the disc or growing modes with a slow growth rate depending on the relative importance of the collective effect of the self-gravity. N -body simulations are performed to test the spontaneous growth of lopsidedness in a pure stellar disc. Both approaches are then compared and interpreted in terms of long-lived global m= 1 instabilities, with almost zero pattern speed. [source] Recombination processes with and without momentum conservation in degenerate InNPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2006E. Valcheva Abstract We report on a theoretical approach in which the two cases of recombination with and without momentum conservation in optically excited high carrier concentration InN are considered. The calculations are used to analyze emission spectra of n-type InN layers of electron concentrations from 7.7 × 1017 to 1.4 × 1019 cm,3 studied in the temperature range between 9 and 100 K. The spectra peak near 0.7 eV and the applicability of the two approaches with increasing carrier concentration is estimated. Different transition mechanisms are considered in order to properly account for the observed features in the spectra. Recombination processes involving acceptor- and donor-like localized states are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Multi-scale analysis of the 25,27 July 2006 convective period over Niamey: Comparison between Doppler radar observations and simulationsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S1 2010Christelle Barthe Abstract The present study investigates the multi-scale processes associated with a sequence of convective events that occurred over Niamey during the period 25,26 July 2006. This period corresponds to the active stage of the first intense monsoon surge over Sahel for 2006. During this two-day period, two successive sequences of mesoscale convective systems (MCSs) were located ahead of and in phase with the trough of an African Easterly Wave (AEW). They were followed by suppressed or isolated convection behind the trough and in the vicinity of the ridge. The large AMMA-SOP dataset, in particular the UHF radar and the MIT Doppler radar in Niamey, are used in combination with a low-resolution (5 km) cloud-resolving model to understand the convection organization and its interaction with the environment. Several initial and boundary conditions have been tested, but only the simulation starting with the ECMWF AMMA reanalysis succeeds in reproducing the observed features; this emphasizes the importance of the initial state. From the simulated MCSs, the along-line component of the apparent source of momentum due to the convection is found to be up to 1 m s,1h,1. It seems that MCSs globally reduce the monsoon flow and generate southerlies at mid levels which can reinforce the rotation of the wind at the passage of the trough. During the afternoon of 26 July, the local convection over Niamey resulted from some favourable factors (humidity, CAPE, CIN) that triggered convection, while inhibiting factors (mid-level dry layer, weaker low-level wind shear pointing to the north, anticyclonic curvature of the streamlines at 700 hPa) prevented it organizing itself and propagating. In particular, the low-level wind shear seems of critical importance. Copyright © 2010 Royal Meteorological Society [source] Evolution of the stable water isotopic composition of the rain sampled along Sahelian squall lines,THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S1 2010Camille Risi Abstract In the Tropics, the stable isotopic composition (HDO, HO) of precipitation is strongly modulated by convective activity. To better understand how convective processes impact the precipitation isotopic composition, we analyze the isotopic composition of rain collected during the passage of four squall lines over the Sahel (Niamey, Niger) in August 2006 during the African Monsoon Multidisciplinary Analysis (AMMA) campaign. The high-frequency sampling (5,10 min) of the precipitation allows us to investigate the evolution of the precipitation isotopic composition in different phases of the squall lines. Despite a large variability among the different squall lines, some robust isotopic features appear: the W shape of the ,18O evolution and the deuterium excess decrease in the first part of the stratiform zone. To understand more quantitatively how convective processes impact the precipitation isotopic composition, a simple stationary two-dimensional transport model including a representation of cloud microphysics and isotopic fractionation is developed and forced by three-dimensional winds retrieved from the Massachusetts Institute of Technology (MIT) radar on 11 August 2006. The model reproduces the robust observed features and a large sensitivity to the squall-line dynamics. This model suggests that the main controlling factors of the isotopic evolution are (1) squall-line dynamics, especially the downward advection of air at the rear of the squall lines, affecting the vapour composition and, by isotopic equilibration, the subsequent precipitation composition and (2) rain re-evaporation. This suggests that water isotopes have the potential to better constrain squall-line dynamics and rain re-evaporation, and to evaluate the representation of convective processes in numerical models. Copyright © 2009 Royal Meteorological Society [source] The symbiotic system CH Cygni: An analysis of the shocked nebulae at different epochsASTRONOMISCHE NACHRICHTEN, Issue 8 2009M. Contini Abstract We analyse the line and continuum spectra of the symbiotic system CH Cygni. We adopt the colliding-wind model to explain the symbiotic system at different phases. Peculiar observed features such as flickering, radio variation, X-ray emission, as well as the distribution of the nebulae and shells throughout the system are investigated by modelling the spectra at different epochs. The models account consistently for shock and photoionization and are constrained by absolute fluxes. We find that the reverse shock between the stars leads to the broad lines observed during the active phases, as well as to radio and hard X-ray emission, while the expanding shock is invoked to explain the data particularly during the transition phases (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||