pinecone/core-2020-05-10-deduplication huggingface dataset:
Towards A Topological G_2 String

We define new topological theories related to sigma models whose target space
is a 7 dimensional manifold of G_2 holonomy. We show how to define the
topological twist and identify the BRST operator and the physical states.
Correlation functions at genus zero are computed and related to Hitchin's
topological action for three-forms. We conjecture that one can extend this
definition to all genus and construct a seven-dimensional topological string
theory. In contrast to the four-dimensional case, it does not seem to compute
terms in the low-energy effective action in three dimensions.Comment: 15 pages, To appear in the proceedings of Cargese 2004 summer schoo
Closed strings in Misner space: a toy model for a Big Bounce ?

Misner space, also known as the Lorentzian orbifold $R^{1,1}/boost$, is one
of the simplest examples of a cosmological singularity in string theory. In
this lecture, we review the semi-classical propagation of closed strings in
this background, with a particular emphasis on the twisted sectors of the
orbifold. Tree-level scattering amplitudes and the one-loop vacuum amplitude
are also discussed.Comment: 30 pages, 3 figures, to appear in the Proceedings of the NATO ASI and
  EC Summer School ``String Theory: from Gauge Interactions to Cosmology'',
  Cargese, France, June 7-19, 200
Nonlinear Quantum Dynamics

The vast majority of the literature dealing with quantum dynamics is
concerned with linear evolution of the wave function or the density matrix. A
complete dynamical description requires a full understanding of the evolution
of measured quantum systems, necessary to explain actual experimental results.
The dynamics of such systems is intrinsically nonlinear even at the level of
distribution functions, both classically as well as quantum mechanically. Aside
from being physically more complete, this treatment reveals the existence of
dynamical regimes, such as chaos, that have no counterpart in the linear case.
Here, we present a short introductory review of some of these aspects, with a
few illustrative results and examples.Comment: 13 pages, 3 figures, invited talk at the NATO Advanced Workshop,
  "Nonlinear Dynamics and Fundamental Interactions," (October, 2004, Tashkent
Seasonal and inter-annual climate forecasting: The new tool for increasing preparedness to climate variability and change in agricultural planning and operations

Climate variability and change affects individuals and societies. Within agricultural systems, seasonal climate forecasting can increase preparedness and lead to better social, economic and environmental outcomes. However, climate forecasting is not the panacea to all our problems in agriculture. Instead, it is one of many risk management tools that sometimes play an important role in decision-making. Understanding when, where and how to use this tool is a complex and multi-dimensional problem. To do this effectively, we suggest a participatory, cross-disciplinary research approach that brings together institutions (partnerships), disciplines (e.g., climate science, agricultural systems science, rural sociology and many other disciplines) and people (scientist, policy makers and direct beneficiaries) as equal partners to reap the benefits from climate knowledge. Climate science can provide insights into climatic processes, agricultural systems science can translate these insights into management options and rural sociology can help determine the options that are most feasible or desirable from a socio-economic perspective. Any scientific breakthroughs in climate forecasting capabilities are much more likely to have an immediate and positive impact if they are conducted and delivered within such a framework. While knowledge and understanding of the socio-economic circumstances is important and must be taken into account, the general approach of integrated systems science is generic and applicable in developed as well as in developing countries. Examples of decisions aided by simulation output ranges from tactical crop management options, commodity marketing to policy decisions about future land use. We also highlight the need to better understand temporal- and spatial-scale variability and argue that only a probabilistic approach to outcome dissemination should be considered. We demonstrated how knowledge of climatic variability (CV), can lead to better decisions in agriculture, regardless of geographical location and socio-economic conditions. \u
Stationary Points of Scalar Fields Coupled to Gravity

We investigate the dynamics of gravity coupled to a scalar field using a
non-canonical form of the kinetic term. It is shown that its singular point
represents an attractor for classical solutions and the stationary value of the
field may occur distant from the minimum of the potential. In this paper
properties of universes with such stationary states are considered. We reveal
that such state can be responsible for modern dark energy density.Comment: H. Kroger, invited talk, FFP6, Udine (2004), revised version with
  corrected author lis
A Quantum Approach to Cosmology

We present a theory based upon the treatment of the gravitational field as a
sea of gravity quanta, as defined elsewhere. The resultant model for the
Universe is a static one, like Einstein first saw, with a new feature: a local
shrinking quantum world that completely explains the Hubble red shift under a
new point of view. The presently accepted expansion of the Universe is
interpreted here as an apparent effect, as seen from the Lab system of
reference. The static Universe has immersed in it a local shrinking atomic
world: a fundamental change in the interpretation of the Hubble's observations.
The conservation principles (momentum, angular momentum and energy) can be
dealt with under 2 different points of view: local (apparent) and COSMOLOGICAL
("real"). The 2 are in complete agreement with observation. They are also free
of well known contradictions or paradoxes/incoherencies (i.e. in the Big Bang
model). By dealing now with very well known first principles (Heisenberg, Mach,
de Broglie, Weinberg's relation) under the same 2 points of view, we arrive at
the conclusion that our new approach is in accordance with the Einstein's field
equations of General Relativity, and Quantum Mechanics. We consider this to be
a promising first step towards the way of dealing with the gravitational field
coherently both from the General Relativity and from the Quantum Mechanical
theories. The agreement with the present values of the cosmological parameters
is very satisfactory.Comment: Presented at the 6th International Symposium Frontiers of Fundamental
  Physics, Udine (Italy), September 26-28 200
GSM and GPRS performance of IPSEC data communication

Cellular Internet services must grapple with the added security threats posed by the radio transmission, open to eavesdropping. Furthermore, the combination of always-on connectivity and an interface to the public Internet means high speed data services has to cope with the same security issues that can be found in the wired environment.Confidentiality of GSM/GPRS communications has been provided only in BSME/GGSN-ME by COMP128/GEA+algorithms, whose strength is often not believed adequate for corporate/governmental requirements. Furthermore, A5/1 and A5/2 algorithms have been recently attacked with real time ciphertext only cryptanalysis by Barkan, Biham and Keller. To provide an adequate level of security, it is often argued to employ IPSec over the GSM/GPRS framework. We provide experimental evidences that IPSec is a viable solution to provide the desired level of security. In particular, the overhead generated is tolerable where high sensitive/critical communications take place. We expect that our findings could help better understanding how securing a deployed GSM/GPRS network which\ud
corporate/governmental infrastructures can rely on and what performances can be expected by using IPsec over these media.Cellular Internet services must grapple with the added security threats posed by the radio transmission, open to eavesdropping. Furthermore, the combination of always-on connectivity and an interface to the public Internet means high speed data services has to cope with the same security issues that can be found in the wired environment.Confidentiality of GSM/GPRS communications has been provided only in BSME/GGSN-ME by COMP128/GEA+algorithms, whose strength is often not believed adequate for corporate/governmental requirements. Furthermore, A5/1 and A5/2 algorithms have been recently attacked with real time ciphertext only cryptanalysis by Barkan, Biham and Keller. To provide an adequate level of security, it is often argued to employ IPSec over the GSM/GPRS framework. We provide experimental evidences that IPSec is a viable solution to provide the desired level of security. In particular, the overhead generated is tolerable where high sensitive/critical communications take place. We expect that our findings could help better understanding how securing a deployed GSM/GPRS network which\ud
corporate/governmental infrastructures can rely on and what performances can be expected by using IPsec over these media.Monograph's chapter
Freeform construction application research

This paper was presented at the International conference on Advances in Engineering Structures, Mechanics and Construction, Waterloo, Ontario, Canada, May 2006 [© Springer]. The definitive version is available at: http://dx/doi.org/10.1007/1-4020-4891-2_65The level of automation technology and processes control, within the construction sector, faces unique challenges if it is to catch up with automotive and aerospace applications. The construction industry has problems relating to health and safety, environmental legislation and traditional methods of procurement. These are compounded by diminishing skills in the labour force. One way to address these issues is by increased automation and integration of design, modelling and process control. Digital Fabrication has demonstrated the feasibility of the integration of design and component production on a large scale. Freeform Construction builds on Digital Fabrication by integrating the control of final material deposition. This paper reports on recent meetings held with industrialists to gauge their perceptions of the technology and encourage discourse to identify both applications and opportunities for the wider research community. Examples of digital fabrication in construction are discussed. Freeform Construction is defined and potential applications are presented. An example of physical model generation from construction CAD software is described
Static and dynamic behaviour of a 3D periodic structure

This contribution deals with the assessment of static and dynamic behavior a 3D-periodic structure. Equivalent Young and shear moduli are evaluated respectively via a spring-network calculation performed on a representative volume element (RVE)of the structure and an energy approach. To assess the accuracy of the two methods, FE simulations are performed, and tensile experiments are conducted on specimens cut out from 3D-structure panels. Results show disagreement for stiffness values along y-direction. This is thought to be due to stiffness variation between RVE's due to boundary conditions. A new analytical/numerical approach is proposed taking into consideration the presence of different types of boundary conditions on RVE's. Static results are further used as an input for FE investigations of the dynamic behavior of the structure. Two models are proposed: a) homogeneous and b) laminated models. Vibration tests are performed on different specimens and fundamental frequencies are noted. Results for both models correlate well with experimental data. However, the homogeneous model is limited to low frequencies
Decision and discovery in defining 'disease'

This version (May 17, 2005) was published in its final form as:

Schwartz PH. Decision and discovery in defining 'disease'. In: Kincaid H, McKitrick J, editors. Establishing medical reality: essays in the metaphysics and epistemology of biomedical science. Dordrecht: Springer; 2007. p. 47-63. http://dx.doi.org/10.1007/1-4020-5216-2_5The debate over how to analyze the concept of disease has often centered on the question of whether to include a reference to values, in particular the ‘disvalue’of diseases, or whether to avoid such notions. ‘Normativists,’such as King ([1954], 1981) and Culver and Gert (1982) emphasize the undesirability of diseases, while ‘Naturalists,’ most prominently Christopher Boorse (1977, 1987, 1997), instead require just the presence of biological dysfunction. The debate between normativism and naturalism often deteriorates into stalemate, with each side able to point out significant problems with the other. It starts to look as if neither approach can work. In this paper, I argue that the standoff stems from deeply questionable assumptions that have been used to formulate the opposing positions and guide the debate. In the end, I propose an alternative set of guidelines that offer a more constructive way to devise and compare theories
Visco-elastic regularization and strain softening

In this paper it is intended to verify the capacity of regularization of the numerical
solution of an elasto-plastic problem with linear strain softening. The finite element method
with a displacement approach is used. Drucker-Prager yield criteria is considered. The radial
return method is used for the integration of the elasto-plastic constitutive relations. An elastovisco-
plastic scheme is used to regularize the numerical solution. Two constitutive laws have
been developed and implemented in a FE-program, the first represent the radial return
method applied to Drucker-Prager yield criteria and the second is a time integration
procedure for the Maxwell visco-elastic model. Attention is paid to finite deformations. An
associative plastic flow is considered in the Drucker-Prager elasto-plastic model. The
algorithms are tested in two problems with softening. Figures showing the capability of the
algorithms to regularize the solution are presented
Tolerance analysis and synthesis by means of deviation domains, axi-symmetric cases

The small displacement torsors are generally used for the represeolation of the geometrical deviations. The standardised tolerances can then be translated by a set of inequalities between the components of a deviation torsor. hi me case of cylindrical possible to reduce the space to three dimensions at the maximum instead of six in the general case. Topological operations like the Minkowski sum to carry OUT the domains presented application relates to metro-logic inspection for a specification with maximum material condition on both the toleranced surface and the datum. The second example makes it possible to determine the deviation between two surfaces belonging to two different parts after mating them by two contact features
Breast ductal computer phantoms

International audienceMost of breast cancers (85%) originate from the epithelium and develop first in the ductolobular structures. Therefore, the mammary epithelium should be investigated in priority by means of an anatomically guided examination. For this purpose (mass screening, surgery navigation), we develop a two-dimensional anatomic phantom which corresponds to an axial cut of the ductolobular structures and enables one to better understand the interaction of the breast composition with ultrasound. The different constitutive tissues are modeled as a random inhomogeneous continuum with density and sound speed fluctuations. Ultrasonic pulse propagation through the breast computer phantom has been simulated using a finite element time domain method (the phantom can be used with others propagation codes). The simulated Ductal Echographic image is compared with the Ductal Tomographic (DT) reconstruction. The preliminary results reveal a higher quality of DT both in terms of contrast and resolution
Compound quantitative ultrasonic tomography of long bones using wavelets analysis

International audienceCompound Quantitative Ultrasonic Tomography (CQUT) is used to long bones imaging. In previous works, we showed that an iterative tool might be used to provide, from reflection tomography, qualitative images of the shape of the object, and to provide, from transmission tomography, quantitative images of the velocity map. Both tomographies are based on ultrasonic propagation in bones, particularly perturbed by this high-contrasted heterogeneous medium. Reflected and transmitted signal are composed of several packages of waves, which had followed various pathways within the cortical shell of long bones. Signal and image processing have a large important part in the complete process. To improve reflection tomography and shape recognition, we used a novel image-processing tool that improves the resolution and, so, the cortical thickness measurement. This image processing is very simple and allows us to initialise the transmission tomography, based on the knowledge of the geometrical properties. The procedure are also based on the knowledge of the acoustical properties of the body because the Time-Of-Flight measured on the extracted ultrasonic signal are related to the useful velocities of the ultrasonic waves throughout the shell. To optimise our signal processing, we propose a novel algorithm based on the wavelet analysis tool adapted to ultrasonic signals that allow the transmitted signals to be cleaned and filtered and the useful information to be separated from the unwanted noise
Ontology-services agent to help in the structural and semantic heterogeneity

In the Virtual Enterprises (VE) environment, interactions between distributed heterogeneous computing entities representing different enterprises, people and resources, take place. These interactions, in order to be both syntactic and semantic compatible, need to follow appropriate standards (ontologies) well understood by all the participants. Even for each domain ontology, people may store their data in different structures and use different terms to represent the same concept. This paper focuses on an effort to create an Ontology-Services Agent to monitor the communication acts taking place in a Multi-agent System. The Ontology-Services Agent provides help in solving the Structural and Semantic Heterogeneity problem, enabling appropriate conversations and making it possible meaningful agreements between agents representing different enterprises and resources in a VE environment
Quadrupedal locomotion : an introduction to the control of four-legged robots

xiv, 267 p.: ilWalking machines have potential advantages over traditional vehicles, and they have already succeeded in carrying out many tasks that wheeled or tracked robots cannot handle. Nevertheless, their use in industry and services is currently limited in scope. Quadrupedal Locomotion: An Introduction to the Control of Four-legged Robots brings together some of the methods and techniques in this emerging field that have recently been developed in an effort to deal with the problems that currently prevent legged robots being more widely used for real applications. Quadrupedal Locomotion: An Introduction to the Control of Four-legged Robots illustrates the appropriate algorithms and methods through a discussion of simulation and experiments that have been tested on a real machine, the SILO4 walking robot. Data from the experiments can be found on-line. This book is divided into two parts: the first part, Walking Measurements and Algorithms, introduces the historical development of quadrupeds, their advantages/disadvantages and potential uses, and the trade-off between quadrupeds and hexapods. The second part, Control Techniques, concentrates on general techniques that have been specifically applied to legged robots, including kinematic and dynamic models, soft computing techniques to increase speed, virtual sensors that help reduce the electronic burden of the machine, and software simulators to study and test certain robot properties. As the first book to focus specifically on quadrupeds, Quadrupedal Locomotion: An Introduction to the Control of Four-legged Robots will be suitable for researchers, postgraduates and senior undergraduates in the field of robotics as well as engineers working in industry.Part I Walking Measurements and Algorithms\ud
Walking Robots\ud
Stability in Walking Robots\ud
Generation of Periodic Gaits\ud
Generation on Non-periodic Gaits\ud
New Approaches to Stability\ud
\ud
Part II Control Techniques\ud
Kinematics and Dynamics\ud
Improving Leg Speed by Soft Computing Techniques\ud
Virtual Sensors for Walking Robots\ud
Human-Machine Interaction\ud
The SIL04 Walking Robot\ud
Simulation Software for Walking RobotsPeer reviewe
Programming, Composing, Deploying for the Grid

Grids raise new challenges in the following way: heterogeneity of underlying machines/networks and runtime environments (types and performance characteristics), not a single administrative domain, versatility. So the need to have appropriate programming and runtime solutions in order to write, deploy then execute applications on such heterogeneous distributed hardware in an effective and efficient manner. We propose in this article a solution to those challenges which takes the form of a programming and deployment framework featuring parallel, mobile, secure and distributed objects and components
Synthesis of OCL pre-conditions for graph transformation rules

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-13688-7_4Proceedings of Third International Conference, ICMT 2010, Malaga, Spain, June 28-July 2, 2010Graph transformation (GT) is being increasingly used in Model Driven Engineering (MDE) to describe in-place transformations like animations and refactorings. For its practical use, rules are often complemented with OCL application conditions. The advancement of rule post-conditions into pre-conditions is a well-known problem in GT, but current techniques do not consider OCL. In this paper we provide an approach to advance post-conditions with arbitrary OCL expressions into pre-conditions. This presents benefits for the practical use of GT in MDE, as it allows: (i) to automatically derive pre-conditions from the meta-model integrity constraints, ensuring rule correctness, (ii) to derive pre-conditions from graph constraints with OCL expressions and (iii) to check applicability of rule sequences with OCL conditions.Work funded by the Spanish Ministry of Science and Innovation through projects “Design and construction of a Conceptual Modeling Assistant” (TIN2008-00444/TIN - Grupo Consolidado), “METEORIC” (TIN2008-02081), mobility grants JC2009-00015 and PR2009-0019, and the R&D program of the Community of Madrid (S2009/TIC-1650, project “e-Madrid”). We would like to thank the anonymous referees and the members of the Conceptual Modeling Group (GMC) at UPC for their useful comments