Synthetic Representation Research Articles

Synthetic representation of the Galilean satellites' orbital motions from L1 ephemerides

Aims. We aim to provide a synthetic representation of the orbital motion of Io, Europa, Ganymede, and Callisto. It corresponds to a quasi-periodic Fourier series whose arguments are integer combinations of the fundamental arguments of the dynamical system, which are also given. Methods. The present series are issued from frequency analysis and digital filtering treatments. The initial samplings have been taken from a former numerical integration fit to the observations and referenced as L1 ephemerides. Results. Our representation allows for the identification of all the significant perturbations in the system, which helps us to understand these orbital motions. It is also useful in other related topics: the dynamical history of the system and studies requiring us to extract only major terms to compute motions such as the rotation of the bodies.

Evaluation of sustainability of a city through fuzzy logic

Abstract The sustainable indicators are characterized by a low degree of aggregation and a high amount of information. An indicator must show a synthetic representation of a real environmental, by using a value or a parameter, so that they can be easily used by policy makers. It is necessary to connect, therefore, the various systems in an appropriately integrated sustainable system. The indicators need to be aggregated based on the structure of the data. Each indicator must to be defined through a weight with reference to another weighted indicator. In this paper is illustrated the calculation of the assigned weights that uses a procedure based on fuzzy logic and to define a model that allows us to estimate the sustainability of a city. The final result is, therefore, a combination of values assigned by expert opinion for the various criteria, processed using fuzzy logic to obtain a weight with significant objectivity and as it is possible to estimate the sustainability of the city through the weights.

Efficient ocular expression analysis for synthetic reproduction

This paper presents an original framework that analyzes the complete ocular (eye + eyebrow) expression on video sequences to reproduce it later on synthetic three-dimensional (3-D) models in real-time. We propose a two step process to develop robust techniques for facial feature analysis aimed at working without special illumination conditions or physical constraints on the user (markers, fixed frontal pose, etc.). First, simple and efficient image-processing methods based on motion models are designed over a frontal point of view of the face. Natural and realistic intra-feature and inter-feature constraints are applied to improve the analysis results. Then, the usability of these algorithms is extended to enable the analysis regardless of the person's pose in front of the camera. This is achieved by redefining the motion models involved over the speaker's highly realistic synthetic representation (clone), by using a suitable observation model, and by predicting the head pose in 3-D, frame by frame.

Ultra-wideband synthetic aperture radar time-frequency representation image formation

In ultra-wideband synthetic aperture radar (UWB SAR) imaging, scatterers often perform the frequency- and aspect angle-dependent reflectivity characteristic, which is usually neglected in traditional imaging processing. A novel UWB SAR time-frequency representation image formation (TFRIF) is proposed to retrieve the frequency- and aspect angle-dependent information, which is valuable in target detection. Based on the TFRIF, two fusion schemes are studied: pixel level fusion (PLF) and decision level fusion (DLF). Based on the analytical expressions, it is concluded that TFRIF can extract the reflectivity pattern information with high precision and little sacrifice of the spatial resolutions. Quantitative analyses of spatial resolutions and detectability improvement of the proposed fusion schemes are tested on airborne UWB SAR data. The real data results validate the proposed TFRIF and its associated PLF and DLF schemes.

From the Editors: “Conversations about Motherland:” In Search of the Chronotope of Empire and Nation

13 Ab Imperio, 2/2006 From the EDITORS In the first issue of the journal in 2006, we offered and substantiated Ab Imperio’s new annual program: “Anthropology of Languages of SelfDescription in Empire and Nation.” The second issue of the journal builds upon the first and approaches “homeland” as a space of immediate personal experience, on the one hand, and as a language in which metaphors such as immediacy, locality, and territoriality are used for the description of group unity, on the other. We have consciously broadened the framework of this issue, which we had initially envisioned as focused on anthropology of languages of (self-)description of “homeland” as part of the experience of transition from the “imperial” to the “national.” Although some of the articles contain interesting perspectives on the latter problem (most clearly Bradley Woodworth’s article, which explores the Estonization of Revel in the Russian Empire and the transformation of Revel into an Estonian “homeland”), other texts remind us that between the local, “anthropological ” definition of “homeland” and the political use of categories that define “homeland” is an extremely porous and flexible border. Very rarely do we meet abstract definitions of “homeland” in the languages of “CONVERSATIONS ABOUT MOTHERLAND:” IN SEARCH OF THE CHRONOTOPE OF EMPIRE AND NATION 14 From the Editors, In Search of the Chronotope of Empire and Nation self-description of nationalism and imperial patriotism: these definitions are more often local, particular, and idiosyncratic. The anthropological aspect of this approach consists in that social practices and roles of people are problematized and perceived as “text” and not as semantically fixed elements of an “alphabet.” The authors of this issue suggest yet another unidentified aspect of the problem and approach, which has turned out to be an interesting additional line of inquiry in this issue. They point to the very category of “space” as a fundamental dimension of thinking and description. This dimension underpins the language of description of social reality and at the same time is subject to historical changes in spatial imagination. Ann Stoler and Carole McGranahan, whose article appears in our methodological section, speak of the necessity of a full-scale reflection on spatial axioms that condition how scholars approach empire. These axioms bring about Eurocentric concepts of core and periphery, colony and colonized, and so forth. By historicizing these concepts, Stoler and McGranahan show how the logic of European imperialism led to a spatialization of thinking, because there was a need in modern categories to order “new” and “unstructured” spaces. The authors plea for a return to the genealogy of these concepts and to demonstrate what the function of these simple spatial dichotomies was and how they ordered (rather than reflected) the reality of dynamically developing empires. Stoler and McGranahan illustrated the opportunities offered by this approach by analyzing the etymology and the historical semantics of the terms “colony” and “colonist.” Similar to the newest revision of the category of “identity,” the study of genealogy of mental spatial “texts” of empire’s diverse elements, from local “homelands” to a synthetic representation of empire as patria, makes us revisit our stereotypes and advances the idea of plural and situational “homelands.” Petr Meilakh’s article on the discourses of homeland among contemporary Meskheti Turks is a good example of this type of analysis. The article by Kelly O’Neill represents another approach to spatial categories of “homeland,” native land, or historical territory in the context of imperial expansion. Exploring the incorporation of the Crimea into the space of the Russian Empire through the “politics of landscape,” the author suggests the presence of three patterns of integration for different layers of historical legacy: the Classic Greek, Genovese, and Muslim (the latter layer is the subject of her detailed analysis). Each of the cultural texts of the Crimean landscape interacted differently with the logic of empire as a common civilizing home and later with the logic of the nationalizing em- 15 Ab Imperio, 2/2006 pire. That the Crimea preserved its multicultural identity even against the background of the Russification of imperial discourses and practices in the nineteenth century makes us reflect upon the relativity of the opposition between empire and nation and suggests...

Fatigue behaviour analysis of mechanical components subject to random bimodal stress process: frequency domain approach

A frequency domain approach to fatigue life evaluation is an important task in the design of mechanical components subject to random loads. The greatest advantages of this method are the computational efficiency and the capability to give a synthetic representation of a random process. The importance of this method is clear, especially when it is used in the postprocessing phase of a numerical analysis, for example Finite Element (FEA) or Multibody (MBS) simulation. The weak step in this procedure is the direct evaluation of the probability density function (pdf) of the cycles amplitude from stress power spectral density (PSD). In fact, the translation to frequency domain of the Rainflow cycle counting is a serious problem but there is a body of important literature concerning this. After reviewing the most important literature from this research field, a new original index to compare the reliability of the frequency domain methods is proposed. This index efficiently achieves this purpose, and a future objective could be to use such index to define a correction factor in order to exactly evaluate the fatigue damage. A very important class of random processes was considered: the bimodal power spectral density (PSD) random processes. The aim of this paper is to identify independent parameters in these processes and through them evaluate the cycles probability density function (pdf) amplitude.

Analogue (plaster) modelling and synthetic seismic representation of hangingwall fault

The complex structuring associated with ramp-flat-ramp extensional master faults, as well as the strain pattern in the hanging-wall fault block of such faults, have been analysed with the help of analogue Plaster of Paris models. This analysis shows that the shallow-dipping master fault commonly develops several fault branches due to either asperity bifurcation or hanging-wall and footwall splaying, and that the deeper parts of steeper early generation faults are sometimes cut by younger faults. This generates a very complex fault pattern in the deeper part of the hanging-wall fault block. Based on the analogue models, the possibility of generating synthetic reflection seismograms by the use of simple modelling techniques (ray tracing and finite-difference models) has been investigated. It is concluded that the two methods produce significantly different results in terms of resolution and noise. The ray-tracing method resulted in a highly idealized image that can be viewed as the end product after an idealized processing sequence in that no noise, no multiples or other artefacts are incorporated. Furthermore, all reflections are in the correct position and are displayed with the correct amplitude in each case. Although the result can be used as a good reference for what can be obtained by simple seismic modelling, the weak aspect of this method is obviously the over-simplified and unrealistically ‘clean’ image presented. A more ‘realistic’ reflection seismic image is obtained in cases where the synthetic seismogram is generated by the finite-difference method. However, the structural features stand out with less clarity, and it is less likely that the interpreter of this section would be able to identify the two master fault planes or to distinguish the complex structural pattern in the deep part of the hanging-wall fault block.

Semiquantitative evaluation of massive rock quality using ground penetrating radar

This work studies a methodology starting from georadar data that allows a semiquantitative evaluation of massive rock quality. The method is based on the concept that in good quality rock, most of the energy is transmitted, while in low quality rock, the energy is backscattered from fractures, strata joints, cavities, etc. When the energy loss due to spherical divergence and attenuation can be recovered by applying a constant spherical/exponential gain, the resulting energy function observed in the georadar section depends only on the backscattered energy. In such cases, it can be assumed that the amount of energy is an index of rock quality. Radar section interpretation is usually based on the reconstruction of reflected high-energy organized events. Thus, no consideration is given to backscattered not-organized energy produced by microfractures that greatly influences the geotechnical characteristics of the rock mass. In order to take into consideration all the backscattered energy, we propose a method based on the calculation of the average energy relative to a portion of predefined rock. The method allows a synthetic representation of the energy distributed throughout the section. The energy is computed as the sum of the square of amplitude of samplings contained inside cells of appropriate dimensions. The resultant section gives a synthetic and immediate mapping of rock quality. The consistency of the method has been tested by comparing georadar data acquired in travertine and limestone quarries, with seismic tomography and images of actual geological sections. The comparison highlights how effectively the energy calculated inside the cells give synthetic representation of the quality of rocks; this can result in maps where the high-energy values correspond to rock of poor quality and the low energy values correspond to a good quality region. The results obtained in this way can, in this case, be partly superimposed onto those of seismic tomography.

Sub-basalt imaging problems and the application of Artificial Neural Networks

In many areas of the world, the presence of shallow high velocity, highly heterogeneous layers complicate seismic imaging of deeper reflectors. Of particular economic interest are areas where potentially hydrocarbon-bearing strata are obscured by layers of basalt. Basalt layers are highly reflective and heterogeneous. Using reflection seismic, top basalt is typified by a high-amplitude, coherent reflector with poor resolution of reflectors below the basalt, and even bottom basalt. Here, we present a new approach to the imaging problem using the pattern recognition abilities of a back-propagation Artificial Neural Network (ANN). ANNs are computational systems that attempt to mimic natural biological neural networks. They have the ability to recognize patterns and develop their own generalizations about a given data set. Back-propagation neural networks are trained on data sets for which the solution is known and tested on the data that are not previously presented to the ANN in order to validate the network result. We show that Artificial Neural Networks, due to their pattern recognition capabilities, can invert the medium statistics based on the seismic character. We produce statistically defined models involving a basalt analogous layer, and calculate full wavefield finite difference synthetic seismograms. We vary basalt layer thickness and source frequency to generate a synthetic model that produces seismic that is similar to real sub-basalt seismic, i.e. high amplitude top basalt reflector and the absence of base basalt and sub-basalt events. Using synthetic shot gathers, generated in a synthetic representation of the sub-basalt case, we can invert the velocity medium standard deviation by using an ANN. By inverting the velocity medium standard deviation, we successfully identified the transition from basalt to sub-basalt on the synthetic shot gathers. We also show that ANNs are capable of identifying the basalt to sub-basalt transition in the presence of incoherent noise. This is important for any future applications of this technique to the real-world seismic data, as this data is never completely noise-free. There is always a certain level of residual (noise remaining after initial noise filtering) environmental/ambient noise present on the recorded seismics, hence, neural network training with noise-free synthetic seismic is less than optimal.

A Procedure To Define The Optimal Grid Size ForThe Exhaustive Extraction Of HydrologicWatershed Drainage Features From A DigitalElevation Model Using A Raster GeographicInformation System

To study the fate of non-point source pollution and other spatial environmental management problems, it is very convenient to generate and to exploit a synthetic representation of the watershed describing the terrestrial and riverine transportation paths of water and contaminants under the action of gravity within a watershed. In raster mode, a drainage algorithm called D8 is often used to identify the flow direction (aspect) from each cell to one of the eight adjacent ones according to the steepest elevation gradient and then to generate the flow accumulation defining a synthetic hydrographic network. Given a specific digital elevation model (DEM), two parameters need to be optimized; firstly, the size of the grid allowing the extraction of all the relief information contained in the available DEM; secondly, a basic unit area necessary to induce a perennial stream, and thus control the density of the generated hydrographic tree. This paper presents a procedure to optimize both parameters in the context of the D8 drainage algorithm; it introduces a new drainage distance concept to replace the classical Euclidean one, to assess the discrepancies between the generated network and the terrain reality derived from the river blue lines drawn on topographic maps. A case study is presented on a small low-relief tributary of the Saint Lawrence River, using as input data the elevation isolines available on 1:20,000 numerical topographic maps and the vector terrain river network as reference. Management Information Systems, C.A. Brebbia & P. Pascolo (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-815-5 226 Management Information Systems

A Hard-Sphere Scheme Used to Model the Viscosity of Two Ternary Mixtures up to 100 MPa

Recently, an extensive experimental study of two different ternary mixtures has been undertaken which aimed at showing the effect of composition, temperature and pressure on viscosity and density. The ternary mixture heptane + methylcyclohexane + 1-methylnaphtalene has been chosen as it can be, in some ways, a synthetic representation of a C5+ distillation fraction of a petroleum crude oil. The ternary mixture water + diacetone-alcohol + 2-propanol has the distinctive feature of involving components which have important interactions. The key issue of this study is the fairly high number of samples within the ternary diagram, as the first mixture is described by 45 compositions and the second one by 66 compositions. The viscosity of both mixtures have then been measured at three temperatures (303.15, 323.15, and 343.15K) and 6 pressures (0.1, 20,40,60,80 and 100 MPa) using a high pressure falling body viscometer which allowed to collect 1998 experimental data. Our entire set of data have then been used to test the hard-sphere scheme developed by J. H. Dymond and M. J. Assael. This model has been developed in order to correlate simultaneously thermal conductivity, viscosity and self-diffusion coefficient data for a wide range of temperature and pressure and is derived from the hard-sphere theory. We have only used the procedure to estimate viscosity and very good results (absolute average deviation equal to 2.3%) are obtained.

Fingerprint classification by directional image partitioning

In this work, we introduce a new approach to automatic fingerprint classification. The directional image is partitioned into homogeneous connected regions according to the fingerprint topology, thus giving a synthetic representation which can be exploited as a basis for the classification. A set of dynamic masks, together with an optimization criterion, are used to guide the partitioning. The adaptation of the masks produces a numerical vector representing each fingerprint as a multidimensional point, which can be conceived as a continuous classification. Different search strategies are discussed to efficiently retrieve fingerprints both with continuous and exclusive classification. Experimental results have been given for the most commonly used fingerprint databases and the new method has been compared with other approaches known in the literature: As to fingerprint retrieval based on continuous classification, our method gives the best performance and exhibits a very high robustness.

Computing and Simplifying 2D and 3D Continuous Skeletons

Skeletons provide a synthetic and thin representation of objects. Therefore, they are useful for shape description. Recent papers have proposed to approximate the skeleton of continuous shapes using the Voronoi graph of boundary points. An original formulation is presented here, using the notion of polyballs (we call polyball any finite union of balls). A preliminary work shows that their skeletons consist of simple components (line segments in 2D and polygons in 3D). An efficient method for simplifying 3D continuous skeletons is also presented. The originality of our approach consists in simplifying the shape without modifying its topology and in including these modifications on the skeleton. Depending on the desired result, we propose two strategies which lead to either surfacical skeletons or wireframe skeletons. Two angular criteria are proposed that allow us to build a size-invariant hierarchy of simplified skeletons.

Technological Regimes and Sectoral Patterns of Innovative Activities

This paper focuses on the relationships between observed patterns of innovative activities within a sector and the related context and underlying microeconomic processes that might account for them. It claims that there are some invariant features (with respect to relative prices and incentives mechanisms) of learning and knowledge accumulation that greatly affect the rate and structure of innovative activity. These features are different across sectors. The paper proposes that the specific pattern of innovative activity of a sector can be explained as the outcome of different technological regimes that are implied by the nature of technology and knowledge. The notion of technological regime provides a synthetic representation of some of the most important economic properties of technologies and of the characteristics of the learning processes that are involved in innovative activities. Copyright 1997 by Oxford University Press.

Forage management in dairy farms: A methodological approach

The concepts of ‘forage functioning’ and ‘field function’ were developed to analyse grassland utilization within the overall management of farms. This approach enabled us to identify functional relations between the main farm components: fields with their agronomic characteristics, field pattern structure, and the whole farm viewed from the angle of forage production management and utilization by the herd. Presentation of the concepts and method is followed by an assessment of method validity tested on two types of farm operation in the French Northern Alps. The conceptual model provides a synthetic representation which explains field utilization within the general production objective of the farm. We chose a formalization process that keeps close to the farmer's practices and their justification of them. The resulting diagnosis may help better adjust decisions to the diversity of situations through dialogue between the farmer and the farm adviser.

Use of sedimentological information for geometric simulation of natural porous media structure

A geometric simulation method was used to develop a three‐dimensional, highly detailed synthetic representation of point bar sediments in the Wabash River system. Geometric simulation methods, in comparison to well‐known second‐order stochastic methods, offer the advantage of being more closely related to depositional processes, which are often similarly conceptualized (i.e., described in terms of shapes of discrete bed forms, trends in grain size, and spatial relationships of defined geologic facies). Multiple scales of geometric variation were defined within a sedimentologically prescribed framework, and shapes of discrete geometric elements were established at each scale. The selected shapes were based on published field studies including sedimentological bed form studies and trench studies in active point bar sediments. The parameterization of the shapes allowed for random variability of the shape descriptors; discrete shapes were then generated and assimilated by computer. Hydraulic conductivity values were assigned to the discrete elements based on reports of observed variations in grain size and field measurements of hydraulic conductivity. The synthetic model, referred to as a numerical aquifer, is being used as the basis for extensive numerical experimentation to study the relationship between natural spatial structure and subsurface flow and transport.

From 3D magnetic resonance images to structural representations of the cortex topography using topology preserving deformations

We propose an algorithm allowing the construction of a structural representation of the cortical topography from a T1-weighted 3D MR image. This representation is an attributed relational graph (ARG) inferred from the 3D skeleton of the object made up of the union of gray matter and cerebro-spinal fluid enclosed in the brain hull. In order to increase the robustness of the skeletonization, topological and regularization constraints are included in the segmentation process using an original method: the homotopically deformable regions. This method is halfway between deformable contour and Markovian segmentation approaches. The 3D skeleton is segmented in simple surfaces (SSs) constituting the ARG nodes (mainly cortical folds). The ARG relations are of two types: first, theSS pairs connected in the skeleton; second, theSS pairs delimiting a gyrus. The described algorithm has been developed in the frame of a project aiming at the automatic detection and recognition of the main cortical sulci. Indeed, the ARG is a synthetic representation of all the information required by the sulcus identification. This project will contribute to the development of new methodologies for human brain functional mapping and neurosurgery operation planning.

Ballistic deficit correction methods for large Ge detectors High counting rate study

A comparative study is carried out for different ballistic deficit correction methods versus input count rate (from 3 to 50 kcounts/s) using four large Ge detectors of about 70% relative efficiency. The present work shows that, at shaping time constants shorter or equal to 2 μs, the Tennelec TC245 linear amplifier in the BDC mode (Hinshaw method) is the best compromise for energy resolution and throughput. At low and moderate input count rates (≤10 kcounts/s) the Ortec 675 Ge resolution enhancer based on the Goulding/Landis method offers excellent energy resolution and throughput at 2 μs shaping time. The energy resolution obtained with the Intertechnique 7201 gated integrator is very sensitive to count rate which lowers the interest in this module. At 3 kcounts/s it works very satisfactorily. All correction methods lead to narrow sum-peaks indistinguishable from single γ lines. More than the classical throughput, the full energy peak throughput is found representative of the pile-up inspection dead time of the corrector circuits. A new synthetic representation, plotting simultaneously energy resolution and throughput versus input count rate, is proposed.

Introduction of knowledge bases in patient's data management system: Role of the user interface

As the number of signals and data to be handled grows in intensive care unit, it is necessary to design more powerful computing systems that integrate and summarize all this information. The manual input of data as e.g. clinical signs and drug prescription and the synthetic representation of these data requires an ever more sophisticated user interface. The introduction of knowledge bases in the data management allows to conceive contextual interfaces. The objective of this paper is to show the importance of the design of the user interface, in the daily use of clinical information system. Then we describe a methodology that uses the man-machine interaction to capture the clinician knowledge during the clinical practice. The different steps are the audit of the user's actions, the elaboration of statistic models allowing the definition of new knowledge, and the validation that is performed before complete integration. A part of this knowledge can be used to improve the user interface. Finally, we describe the implementation of these concepts on a UNIX platform using OSF/MOTIF graphical interface.

Sea-surface partial pressure of carbon dioxide in the eastern equatorial Pacific (August 1991 to October 1992): A multivariate analysis of physical and biological factors

Underway PCO 2 measurements were made every three months from a merchant ship in the equatorial Pacific Ocean. The shipping track from Panama to Tahiti crosses the equator near 100°W, collecting PCO 2, sea surface temperature (SST), fluorescence of chlorophyll, nitrate concentration and depth of the mixed layer. The survey started in August 1991, with strong upwelling conditions and PCO 2 peaking at 484 μatm right at the equator. Equatorial warming in November 1991 and decreased upwelling occurred with maximum PCO 2 at 460 μatm, at 2°30′S. With the advent of the 1992 El Niño, and the collapse of equatorial upwelling, PCO 2 was drastically reduced in March 1992. The maximum of PCO 2 was only 397 μatm at 0°40′S, and values greater than 380 μatm spread southward to 6°S. Nitrate concentration, however, was still high between the equator and 10°S. With return to normal conditions in June 1992, PCO 2 rose to 437 μatm at 2°30′S, and in October 1992 strong upwelling brought CO 2-rich water to the surface, with maximum PCO 2 at 0°12′N, at 480 μatm. Multivariate analysis of the data between 7°N and 20°S, after normalization, shows that 60% of the total variance could be explained by the first eigenvector, in which PCO 2, nitrate and fluorescence were opposed to SST. The empirical orthogonal function (EOF) associated to this eigenvector was maximum at or near the equator and decreased abruptly to the north but gradually to the south. This EOF and the corresponding eigenvector could be interpreted as a synthetic representation of the influence of upwelling and of the main processes that modify PCO 2: biological carbon uptake and heating. The variations of the depth of the mixed layer (taken as the depth where temperature was 1°C below SST) were uncorrelated with PCO 2. A strong correlation ( r = 0.97, n = 5) was found between the temperature of upwelled waters (i.e. the minimum SST observed near the equator) and the average PCO 2 between 0° and 5°S.