23,612 research outputs found
Optimizing Event-Driven Simulations
Event-driven molecular dynamics is a valuable tool in condensed and soft
matter physics when particles can be modeled as hard objects or more generally
if their interaction potential can be modeled in a stepwise fashion. Hard
spheres model has been indeed widely used both for computational and
theoretical description of physical systems. Recently further developments of
computational techniques allow simulations of hard rigid objects of generic
shape. In present paper we will present some optimizations for event-driven
simulations that offered significant speedup over previous methods. In
particular we will describe a generalization of well known linked list method
and an improvement on nearest neighbor lists method recently proposed by us.Comment: Submitted to Comp. Phys. Comm. Special Issue for CCP201
CaSPiS: A Calculus of Sessions, Pipelines and Services
Service-oriented computing is calling for novel computational models and languages with well
disciplined primitives for client-server interaction, structured orchestration and unexpected events handling. We present CaSPiS, a process calculus where the conceptual abstractions of sessioning and pipelining play a central role for modelling service-oriented systems. CaSPiS sessions are two-sided, uniquely named and can be nested. CaSPiS pipelines permit orchestrating the flow of data produced by different sessions. The calculus is also equipped with operators for handling (unexpected) termination of the partnerâs side of a session. Several examples are presented to provide evidence of the flexibility of the chosen set of primitives. One key contribution is a fully abstract encoding of Misra et al.âs orchestration language Orc. Another main result shows that in CaSPiS it is possible to program a âgraceful terminationâ of nested sessions, which guarantees that no session is forced to hang forever after the loss of its partner
Focusing on soil-foundation heterogeneity through high-resolution electrical and seismic tomography
The reconstruction of the current status of a historic building is essential for seismic safety assessment and for designing the retrofitting interventions since different safety and confidence factors have to be assumed, depending on the level of information about the subsoil structure. In this work, we present an investigation of the shallow subsurface below and around a historic building affected by differential settlements in order to define its geometry and to characterise its stiffness at low strain. To this end, we employed high-resolution electrical resistivity and seismic (both P-wave and S-wave) tomographies. A three-dimensional electrical resistivity tomography survey was performed to obtain more information about the type and the maximum depth of the building foundation. Electrical resistivity and seismic tomographies were carried out alongside the building, aimed at imaging the top soils and the near-surface geometry. The corresponding inverted models pointed out a remarkable heterogeneity of the shallow subsoil below the building, which is partly founded on a weathered layer and partly on a more rigid lithotype. This heterogeneity is probably a concurrent cause of the building's instability under both static and seismic loading. Our results demonstrate that the man-made fillings and the top soils have to be thoroughly investigated to fully understand the soil-structure behaviour. In this light, the integration of non-invasive high-resolution geophysical techniques, especially tomographic methods, has been proved to properly address the problem of imaging the shallow subsoil
A QUIC Implementation for ns-3
Quick UDP Internet Connections (QUIC) is a recently proposed transport
protocol, currently being standardized by the Internet Engineering Task Force
(IETF). It aims at overcoming some of the shortcomings of TCP, while
maintaining the logic related to flow and congestion control, retransmissions
and acknowledgments. It supports multiplexing of multiple application layer
streams in the same connection, a more refined selective acknowledgment scheme,
and low-latency connection establishment. It also integrates cryptographic
functionalities in the protocol design. Moreover, QUIC is deployed at the
application layer, and encapsulates its packets in UDP datagrams. Given the
widespread interest in the new QUIC features, we believe that it is important
to provide to the networking community an implementation in a controllable and
isolated environment, i.e., a network simulator such as ns-3, in which it is
possible to test QUIC's performance and understand design choices and possible
limitations. Therefore, in this paper we present a native implementation of
QUIC for ns-3, describing the features we implemented, the main assumptions and
differences with respect to the QUIC Internet Drafts, and a set of examples.Comment: 8 pages, 4 figures. Please cite it as A. De Biasio, F. Chiariotti, M.
Polese, A. Zanella, M. Zorzi, "A QUIC Implementation for ns-3", Proceedings
of the Workshop on ns-3 (WNS3 '19), Firenze, Italy, 201
Focusing on Soil Foundation Heterogeneity through High-resolution Tomography
An historical building affected by differential settlements, which were triggered by an earthquake, is
investigated by means of high-resolution tomography, both electrical and seismic. The objective is to
image the geometric structure of the shallow soil below the building and to characterize its stiffness at low
strain.
A preliminary reconstruction of the geological units has been recovered through the combined use of
electrical and seismic data, where the depth of the travertine bedrock varies significantly within the study
site. The range of variation of the main geophysical parameters (resistivity, P- and S-wave velocities)
inferred from these models has been set as reference point for tuning the results obtained from the
geophysical survey performed near the building. The inverted tomographic models obtained from data
acquired alongside the building exhibit heterogeneity of the shallow subsoil, which is partly founded on a
weathered layer and partly on a more rigid lithotype, probably a fractured travertine or a gravel layer.
Therefore the fill anthropic soils can play a relevant role for the structural stability in case of shallow
foundations built on a heterogeneous subsoil
Exogenous underdevelopment pattern
The main dynamics of capitalism is the creation of overproduction in order to search for an internal and foreign market outlet. While increasing the overproduction, both the expansion process and the internationalization of consumption raise. The context just described leads to think about the existence of rich and emerging economies producing an excess of supply compared with their internal demand (net supply) that must be allocated to the poor economies showing an excess of demand compared with their internal supply (net demand). We are, after all, in the compensating structure of the world economy, where the poor countries are setting against the rich and emerging countries; these last two are in competition with each other. Besides, the poor countries absorb the surplus of the rich and emerging ones. The assertion of monetarism, in the last decades, encouraging the market outlets abroad to the detriment of the outlets towards the public sector, leads to stress the tensions between the advantaged and disadvantaged nations. This context makes more doubtful the future economical perspectives. The compensating structure of the world economy facilitates the exogenous nature of the underdevelopment of wide areas of the planet that are addressed to absorb the productive excesses of the advanced economies. The purpose of this current theoretical contribution is just to formalize, through an appropriate economical and mathematical pattern, the interdependence between the strong economical world and the weak economical world.Monetarism; Underdevelopment; Market outlet; Overproduction.
How private is private information?:The ability to spot deception in an economic game
We provide experimental evidence on the ability to detect deceit in a buyer-seller game with asymmetric information. Sellers have private information about the buyer's valuation of a good and sometimes have incentives to mislead buyers. We examine if buyers can spot deception in face-to-face encounters. We vary (1) whether or not the buyer can interrogate the seller, and (2) the contextual richness of the situation. We find that the buyers' prediction accuracy is above chance levels, and that interrogation and contextual richness are important factors determining the accuracy. These results show that there are circumstances in which part of the information asymmetry is eliminated by people's ability to spot deception
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