Strengthening measurements from the edges: application-level packet loss rate estimation

Network users know much less than ISPs, Internet exchanges and content providers about what happens inside the network. Consequently users cannot either easily detect network neutrality violations or readily exercise their market power by knowledgeably switching ISPs. This paper contributes to the ongoing efforts to empower users by proposing two models to estimate -- via application-level measurements -- a key network indicator, i.e., the packet loss rate (PLR) experienced by FTP-like TCP downloads. Controlled, testbed, and large-scale experiments show that the Inverse Mathis model is simpler and more consistent across the whole PLR range, but less accurate than the more advanced Likely Rexmit model for landline connections and moderate PL

Network Neutrality Inference

When can we reason about the neutrality of a network based on external observations? We prove conditions under which it is possible to (a) detect neutrality violations and (b) localize them to specific links, based on external observations. Our insight is that, when we make external observations from different vantage points, these will most likely be inconsistent with each other if the network is not neutral. Where existing tomographic techniques try to form solvable systems of equations to infer network properties, we try to form unsolvable systems that reveal neutrality violations. We present an algorithm that relies on this idea to identify sets of non-neutral links based on external observations, and we show, through network emulation, that it achieves good accuracy for a variety of network conditions

Measuring track vertical stiffness through dynamic monitoring

[EN] This paper proposes a methodology for the evaluation of the track condition by means of the measurement of the track stiffness. This magnitude is calculated from vertical acceleration data measured at the axle box of trains during their normal operation. From the corresponding vertical acceleration spectra, the dominant vibration frequencies for each track stretch are identified and the combined stiffness is then determined. Then the stiffness without the contribution of the rail is calculated. The results obtained for a High Speed ballasted track in several track stretches are within the range 120-130 kN/mm, a result consistent with direct stiffness measurements taken during previous studies. Therefore, the proposed methodology may be used to obtain a first insight to the track condition by means of a continuous measurement of the track combined stiffness. This offers an alternative to traditional stationary stiffness measuring devices and might be a useful complement to dedicated continuous monitoring vehicles.Cano, MJ.; Martínez Fernández, P.; Insa Franco, R. (2016). Measuring track vertical stiffness through dynamic monitoring. Proceedings of the Institution of Civil Engineers - Transport. 169(1). doi:10.1680/jtran.14.00081S169

Human Factors Analysis to Improve the Processing of Ares-1 Launch Vehicle

This slide presentation reviews the use of Human Factors analysis in improving the ground processing procedures for the Ares-1 launch vehicle. The light vehicle engineering designers for Ares-l launch vehicle had to design the flight vehicle for effective, efficient and safe ground operations in the cramped dimensions in a rocket design. The use of a mockup of the area where the technician would be required to work proved to be a very effective method to promote the collaboration between the Ares-1 designers and the ground operations personnel

Analysis of the performance of under-sleeper pads in highspeed line transition zones

[EN] In many high-speed railway lines, the zones between embankments and structures may present some discontinuities, in terms of track geometry and track stiffness, which may create discomfort for passengers, induce deterioration of track and vehicle materials and even raise the risk of derailment to dangerous levels. In the attempt to attenuate the consequences of such problems, some solutions pointing at progressively changing the vertical stiffness in the railway track have been tested, such as transition zones or pads placed either between the rails and the sleepers or under the sleepers. The contribution of under-sleeper pads in transition regions and their effect on the railway infrastructure is specifically analysed in the present paper. The results obtained are of interest since they provide useful information for railway managers on infrastructure design and justify the need to implement such transition ones.Insa Franco, R.; Salvador Zuriaga, P.; Inarejos Mesa, J.; Medina González, L. (2014). Analysis of the performance of under-sleeper pads in highspeed line transition zones. Proceedings of the Institution of Civil Engineers - Transport. 167(2):63-77. doi:10.1680/tran.11.00033S6377167

Bioinformatic evidence for a widely distributed, ribosomally produced electron carrier precursor, its maturation proteins, and its nicotinoprotein redox partners

<p>Abstract</p> <p>Background</p> <p>Enzymes in the radical SAM (rSAM) domain family serve in a wide variety of biological processes, including RNA modification, enzyme activation, bacteriocin core peptide maturation, and cofactor biosynthesis. Evolutionary pressures and relationships to other cellular constituents impose recognizable grammars on each class of rSAM-containing system, shaping patterns in results obtained through various comparative genomics analyses.</p> <p>Results</p> <p>An uncharacterized gene cluster found in many Actinobacteria and sporadically in Firmicutes, Chloroflexi, Deltaproteobacteria, and one Archaeal plasmid contains a PqqE-like rSAM protein family that includes Rv0693 from <it>Mycobacterium tuberculosis</it>. Members occur clustered with a strikingly well-conserved small polypeptide we designate "mycofactocin," similar in size to bacteriocins and PqqA, precursor of pyrroloquinoline quinone (PQQ). Partial Phylogenetic Profiling (PPP) based on the distribution of these markers identifies the mycofactocin cluster, but also a second tier of high-scoring proteins. This tier, strikingly, is filled with up to thirty-one members per genome from three variant subfamilies that occur, one each, in three unrelated classes of nicotinoproteins. The pattern suggests these variant enzymes require not only NAD(P), but also the novel gene cluster. Further study was conducted using SIMBAL, a PPP-like tool, to search these nicotinoproteins for subsequences best correlated across multiple genomes to the presence of mycofactocin. For both the short chain dehydrogenase/reductase (SDR) and iron-containing dehydrogenase families, aligning SIMBAL's top-scoring sequences to homologous solved crystal structures shows signals centered over NAD(P)-binding sites rather than over substrate-binding or active site residues. Previous studies on some of these proteins have revealed a non-exchangeable NAD cofactor, such that enzymatic activity <it>in vitro </it>requires an artificial electron acceptor such as N,N-dimethyl-4-nitrosoaniline (NDMA) for the enzyme to cycle.</p> <p>Conclusions</p> <p>Taken together, these findings suggest that the mycofactocin precursor is modified by the Rv0693 family rSAM protein and other enzymes in its cluster. It becomes an electron carrier molecule that serves <it>in vivo </it>as NDMA and other artificial electron acceptors do <it>in vitro</it>. Subclasses from three different nicotinoprotein families show "only-if" relationships to mycofactocin because they require its presence. This framework suggests a segregated redox pool in which mycofactocin mediates communication among enzymes with non-exchangeable cofactors.</p