Slope stability in slightly fissured claystones and marls

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-014-0526-5The paper deals with the behavior of some characteristic soft rocks found in the Iberian Peninsula. In geological terms, they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behavior; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases, instability phenomena are addressed in connection with several case histories. Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given. Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels. A recent long-term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations. Persistent discontinuities and, in particular, sedimentation planes play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales. Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.Peer ReviewedPostprint (author's final draft

Analysis of Https Overhead and Minimal Web Certificate Chain of Trust

The popularity of the web is indisputable. With the recent revelations about NSA spying and the increased need for privacy and security, the default use of secure web through TLS/SSL connections has been highlighted. However, the push back against enabling secure web connections by default is due to the increase in communication and processing time.In this work, we quantify the communication time for http and https download times for the most popular websites. The average download time over http non-persistent connection is 2.72 seconds while the average download time over https non-persistent connection is 3.156 seconds. The overhead in using encryption is thus only 436 milliseconds (about 4 round trip times on the Internet) or 16.1% for non-persistent connections. And for persistent connections the overhead is 15%. We thus make the case that https should be enabled by default due to the very low communications overhead. With the recent hacks and breaches at various certificate authorities and no-longer-trusted certificate authorities, we also quantified which certificate authorities are most popular on the Internet. By only trusting ten certificate authorities, a webbrowser can access almost 80% of https-enabled websites. The number of trusted certificate authorities can thus be reduced from thousands to a few dozen.Computer Scienc

Improving the performance of HTTP over high bandwidth-delay product circuits

As the WWW continues to grow, providing adequate bandwidth to countries remote from the geographic and topological center of the network, such as those in the Asia/Pacific, becomes more and more difficult. To meet the growing traffic needs of the Internet some Network Service Providers are deploying satellite connections. Through discrete event simulation of a real HTTP workload with differing international architectures this paper is able to give guidance on the architecture that should be deployed for long distance, high capacity Internet links. We show that a significant increase in the time taken to fetch HTTP requests can be expected when traffic is moved from a long distance international terrestrial link to a satellite link. We then show several modifications to the network architecture that can be used to greatly improve the performance of a satellite link. These modifications include the use of an asymmetric satellite link, the multiplexing of multiple HTTP requests onto a single TCP connection and the use of HTTP1.1

Improving the Deductive System DES with Persistence by Using SQL DBMS's

This work presents how persistent predicates have been included in the in-memory deductive system DES by relying on external SQL database management systems. We introduce how persistence is supported from a user-point of view and the possible applications the system opens up, as the deductive expressive power is projected to relational databases. Also, we describe how it is possible to intermix computations of the deductive engine and the external database, explaining its implementation and some optimizations. Finally, a performance analysis is undertaken, comparing the system with current relational database systems.Comment: In Proceedings PROLE 2014, arXiv:1501.0169

Vena cava anomalies in thoracic surgery

Background: Vena cava anomalies are a rare group of anatomical variations due to an incorrect development of the superior or inferior vena cava during fetal life. They generally show no clinical relevance and the diagnosis is done due to the association with congenital heart diseases in most of cases. However, preoperative identification of these anomalies is mandatory for surgeons to proper surgical planning. If not recognized, lethal complications may occur, as already reported in literature. Case presentation: We report a case series of three different unidentified vena cava anomalies in patients undergoing lung resection. These unrecognized anomalies led to minor complications in two cases and required an accurate intraoperative evaluation in another. A careful retrospective evaluation of preoperative radiological images showed the anomalies. Conclusions: A careful evaluation of the vena cava anatomy at pre-operative imaging is mandatory for thoracic surgeons to properly plan the surgery and avoid complications

SDN Architecture and Southbound APIs for IPv6 Segment Routing Enabled Wide Area Networks

The SRv6 architecture (Segment Routing based on IPv6 data plane) is a promising solution to support services like Traffic Engineering, Service Function Chaining and Virtual Private Networks in IPv6 backbones and datacenters. The SRv6 architecture has interesting scalability properties as it reduces the amount of state information that needs to be configured in the nodes to support the network services. In this paper, we describe the advantages of complementing the SRv6 technology with an SDN based approach in backbone networks. We discuss the architecture of a SRv6 enabled network based on Linux nodes. In addition, we present the design and implementation of the Southbound API between the SDN controller and the SRv6 device. We have defined a data-model and four different implementations of the API, respectively based on gRPC, REST, NETCONF and remote Command Line Interface (CLI). Since it is important to support both the development and testing aspects we have realized an Intent based emulation system to build realistic and reproducible experiments. This collection of tools automate most of the configuration aspects relieving the experimenter from a significant effort. Finally, we have realized an evaluation of some performance aspects of our architecture and of the different variants of the Southbound APIs and we have analyzed the effects of the configuration updates in the SRv6 enabled nodes

Semi-persistent RRC protocol for machine-type communication devices in LTE networks

In this paper, we investigate the design of a radio resource control (RRC) protocol in the framework of long-term evolution (LTE) of the 3rd Generation Partnership Project regarding provision of low cost/complexity and low energy consumption machine-type communication (MTC), which is an enabling technology for the emerging paradigm of the Internet of Things. Due to the nature and envisaged battery-operated long-life operation of MTC devices without human intervention, energy efficiency becomes extremely important. This paper elaborates the state-of-the-art approaches toward addressing the challenge in relation to the low energy consumption operation of MTC devices, and proposes a novel RRC protocol design, namely, semi-persistent RRC state transition (SPRST), where the RRC state transition is no longer triggered by incoming traffic but depends on pre-determined parameters based on the traffic pattern obtained by exploiting the network memory. The proposed RRC protocol can easily co-exist with the legacy RRC protocol in the LTE. The design criterion of SPRST is derived and the signalling procedure is investigated accordingly. Based upon the simulation results, it is shown that the SPRST significantly reduces both the energy consumption and the signalling overhead while at the same time guarantees the quality of service requirements

An empirical study of power consumption of Web-based communications in mobile phones

Currently, mobile devices are the most popular pervasive computing device, and they are becoming the primer way for Web access. Energy is a critical resource in such pervasive computing devices, being network communication one of the primary energy consuming operations in mobile apps. Indeed, web-based communication is the most used, but also energy demanding. So, mobile web developers should be aware of how much energy consumes the different web-based communication alternatives. The goal of this paper is to measure and compare the energy consumption of three asynchronous Web-based methods in mobile devices. Our experiments consider three different Web applications models that allow a web server to push data to a browser: Polling, Long Polling and WebSockets. The obtained results are analyzed to get more accurate understanding of the impact in energy consumption of a mobile browser for each of these three methods. The utility of these experiments is to show developers what are the factors that influence the energy consumption when different web-based asynchronous communication is used. With this information mobile web developers could reduce the power consumption of web applications on mobile devices, by selecting the most appropriate method for asynchronous server communication.MUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech