Is Explicit Congestion Notification usable with UDP?

We present initial measurements to determine if ECN is usable with UDP traffic in the public Internet. This is interesting because ECN is part of current IETF proposals for congestion control of UDPbased interactive multimedia, and due to the increasing use of UDP as a substrate on which new transport protocols can be deployed. Using measurements from the author’s homes, their workplace, and cloud servers in each of the nine EC2 regions worldwide, we test reachability of 2500 servers from the public NTP server pool, using ECT(0) and not-ECT marked UDP packets. We show that an average of 98.97% of the NTP servers that are reachable using not-ECT marked packets are also reachable using ECT(0) marked UDP packets, and that ~98% of network hops pass ECT(0) marked packets without clearing the ECT bits. We compare reachability of the same hosts using ECN with TCP, finding that 82.0% of those reachable with TCP can successfully negotiate and use ECN. Our findings suggest that ECN is broadly usable with UDP traffic, and that support for use of ECN with TCP has increased

Hairpins in the conformations of a confined polymer

If a semiflexible polymer confined to a narrow channel bends around by 180 degrees, the polymer is said to exhibit a hairpin. The equilibrium extension statistics of the confined polymer are well understood when hairpins are vanishingly rare or when they are plentiful. Here we analyze the extension statistics in the intermediate situation via experiments with DNA coated by the protein RecA, which enhances the stiffness of the DNA molecule by approximately one order of magnitude. We find that the extension distribution is highly non-Gaussian, in good agreement with Monte Carlo simulations of confined discrete wormlike chains. We develop a simple model that qualitatively explains the form of the extension distribution. The model shows that the tail of the distribution at short extensions is determined by conformations with one hairpin.Comment: Revised version. 22 pages, 7 figures, 2 tables, supplementary materia

Offloading SLAM for Indoor Mobile Robots with Edge-Fog-Cloud Computing

Indoor mobile robots are widely used in industrial environments such as large logistic warehouses. They are often in charge of collecting or sorting products. For such robots, computation-intensive operations account for a significant per- centage of the total energy consumption and consequently affect battery life. Besides, in order to keep both the power con- sumption and hardware complexity low, simple micro-controllers or single-board computers are used as onboard local control units. This limits the computational capabilities of robots and consequently their performance. Offloading heavy computation to Cloud servers has been a widely used approach to solve this problem for cases where large amounts of sensor data such as real-time video feeds need to be analyzed. More recently, Fog and Edge computing are being leveraged for offloading tasks such as image processing and complex navigation algorithms involving non-linear mathematical operations. In this paper, we present a system architecture for offloading computationally expensive localization and mapping tasks to smart Edge gateways which use Fog services. We show how Edge computing brings computational capabilities of the Cloud to the robot environment without compromising operational reliability due to connection issues. Furthermore, we analyze the power consumption of a prototype robot vehicle in different modes and show how battery life can be significantly improved by moving the processing of data to the Edge layer

Offloading SLAM for Indoor Mobile Robots with Edge, Fog, Cloud Computing

Indoor mobile robots are widely used in industrial environments such as large logistic warehouses. They are often in charge of collecting or sorting products. For such robots, computation-intensive operations account for a significant per- centage of the total energy consumption and consequently affect battery life. Besides, in order to keep both the power con- sumption and hardware complexity low, simple micro-controllers or single-board computers are used as onboard local control units. This limits the computational capabilities of robots and consequently their performance. Offloading heavy computation to Cloud servers has been a widely used approach to solve this problem for cases where large amounts of sensor data such as real-time video feeds need to be analyzed. More recently, Fog and Edge computing are being leveraged for offloading tasks such as image processing and complex navigation algorithms involving non-linear mathematical operations. In this paper, we present a system architecture for offloading computationally expensive localization and mapping tasks to smart Edge gateways which use Fog services. We show how Edge computing brings computational capabilities of the Cloud to the robot environment without compromising operational reliability due to connection issues. Furthermore, we analyze the power consumption of a prototype robot vehicle in different modes and show how battery life can be significantly improved by moving the processing of data to the Edge layer

Extension of nano-confined DNA: quantitative comparison between experiment and theory

The extension of DNA confined to nanochannels has been studied intensively and in detail. Yet quantitative comparisons between experiments and model calculations are difficult because most theoretical predictions involve undetermined prefactors, and because the model parameters (contour length, Kuhn length, effective width) are difficult to compute reliably, leading to substantial uncertainties. Here we use a recent asymptotically exact theory for the DNA extension in the "extended de Gennes regime" that allows us to compare experimental results with theory. For this purpose we performed new experiments, measuring the mean DNA extension and its standard deviation while varying the channel geometry, dye intercalation ratio, and ionic buffer strength. The experimental results agree very well with theory at high ionic strengths, indicating that the model parameters are reliable. At low ionic strengths the agreement is less good. We discuss possible reasons. Our approach allows, in principle, to measure the Kuhn length and effective width of a single DNA molecule and more generally of semiflexible polymers in solution.Comment: Revised version, 6 pages, 2 figures, 1 table, supplementary materia

Intense Mass Loss from C-rich AGB Stars at low Metallicity?

We argue that the energy injection of pulsations may be of greater importance to the mass-loss rate of AGB stars than metallicity, and that the mass-loss trend with metallicity is not as simple as sometimes assumed. Using our detailed radiation hydrodynamical models that include dust formation, we illustrate the effects of pulsation energy on wind properties. We find that the mass-loss rate scales with the kinetic energy input by pulsations as long as a dust-saturated wind does not occur, and all other stellar parameters are kept constant. This includes the absolute abundance of condensible carbon (not bound in CO), which is more relevant than keeping the C/O-ratio constant when comparing stars of different metallicity. The pressure and temperature gradients in the atmospheres of stars, become steeper and flatter, respectively, when the metallicity is reduced, while the radius where the atmosphere becomes opaque is typically associated with a higher gas pressure. This effect can be compensated for by adjusting the velocity amplitude of the variable inner boundary (piston), which is used to simulate the effects of pulsation, to obtain models with comparable kinetic-energy input. Hence, it is more relevant to compare models with similar energy-injections than of similar velocity amplitude. Since there is no evidence for weaker pulsations in low-metallicity AGB stars, we conclude that it is unlikely that low-metallicity C-stars have a lower mass-loss rate, than their more metal-rich counterparts with similar stellar parameters, as long as they have a comparable amount of condensible carbon.Comment: 4 pages, 3 figures. Accepted for publication in A&A. Updated after language editing. Additional typos fixe

From the Unimate to the Delta Robot: The Early Decades of Industrial Robotics

In this paper, the early decades of the history of industrial robots (from the 1950\u2019s to the beginning of the 1990\u2019s, approximately) will be described. The history of industrial robotics can be considered starting with Unimate, the first industrial robot designed and built by Devol and Engelberger. The subsequent evolutions of industrial robotics are described in the manuscript, taking into account both the technical and the economic point of view, until the beginning of the 1990\u2019s, when new kinematic structures (parallel robots) appeared, allowing high-speed operations

Silicate and oxide inclusion characteristics and infra-red absorption analysis of diamonds from the Klipspringer kimberlites, South Africa

The diamonds associated with the 148 Ma Group II Klipspringer kimberlite dyke system emplaced on the Thabazimbi-Murchison Lineament are predominantly of eclogitic origin, and in a parallel study have been demonstrated to have a late Archean origin. Fourier Transform Infra-Red (FTIR) analysis of diamond plates demonstrates complex intergrowth of N-rich and N-poor diamond. Two groups of diamonds occurring in both the Main Fissure and the Sugarbird Blow have been recognised with time averaged mantle residence temperatures (MRT) based on nitrogen aggregation of approximately 1090°C (low-T) and 1170°C (high-T) respectively. In some cases a core of high-T diamond is enclosed within an envelope of low-T diamond. At Marsfontein, a third diamond population with an MRT < 1070°C is present that has not been recorded in diamonds from the Main Fissure or the Sugarbird Blow. Observed lamination lines attest to a deformation event having affected most of the high-T diamonds. A correlation between hydrogen and the ratio between nitrogen present in B aggregates and platelet peak intensity suggests that the presence of hydrogen affects the formation of platelets. Mineral inclusions in the diamonds are predominantly eclogitic (sulfide, garnet, clinopyroxene, kyanite, coesite and rutile). The garnets and clinopyroxenes have a wide range in compositions, extending the worldwide fields for diamond inclusions. The garnets define four groups, one of which is grospyditic and the individual groups display inter-element correlations, which are consistent with magmatic fractionation. The clinopyroxenes include a high aluminium group exhibiting cation site deficiencies (7 to 28% pseudojadeite). Garnets from all four groups, the high aluminium clinopyroxenes and other clinopyroxenes of widely different compositions occur in both the high-T and low-T diamonds. Estimated bulk compositions for diamond bearing eclogite are akin to MOR cumulates from the S.W. Indian Ridge. Thermobarometric estimates for four non-touching garnet-clinopyroxene inclusion pairs in low-T diamonds are within the range 1152 to 1233°C at 50kb. It is considered that the high-T Klipspringer diamonds formed in the Archean and underwent deformation followed by the low-T diamond formation in the host-rock to the high-T diamonds. The deformation event might have been associated with reactivation of the Thabazimbi-Murchison Lineament. The most likely protolith for the diamonds is subducted oceanic crust in which the inclusions of the low temperature diamonds formed by re-crystallisation of pre-existing minerals. At or shortly after the low-T diamond formation, a cool (37 to 39mW/m?) geotherm was established within this part of the Kaapvaal craton. The diamonds survived the emplacement of the Bushveld Igneous Complex and were subsequently sampled and transported by their host kimberlites in the late Jurassic