Small Set Of Elements Research Articles

Breaking Cuckoo Hash: Black Box Attacks

Introduced less than twenty years ago, cuckoo hashing has a number of attractive features like a constant worst case number of memory accesses for queries and close to full memory utilization. Cuckoo hashing has been widely adopted to perform exact matching of an incoming key with a set of stored (key, value) pairs in both software and hardware implementations. This widespread adoption makes it important to consider the security of cuckoo hashing. Most hash based data structures can be attacked by generating collisions that reduce their performance. In fact, for cuckoo hashing collisions could lead to insertion failures which in some systems would lead to a system failure. For example, if cuckoo hashing is used to perform Ethernet lookup and a given MAC address cannot be added to the cuckoo hash, the switch would not be able to correctly forward frames to that address. Previous works have shown that this can be done when the attacker knows the hash functions used in the implementation. However, in many cases the attacker would not have that information and would only have access to the cuckoo hash operations to perform insertions, removals or queries. This article considers the security of a cuckoo hash to an attacker that has only a black box access to it. The analysis shows that by carefully performing user operations on the cuckoo hash, the attacker can force insertion failures with a small set of elements. The proposed attack has been implemented and tested for different configurations to demonstrate its feasibility. The fact that cuckoo hash can be broken with only access to its user functions should be taken into account when implementing it in critical systems. The article also discusses potential approaches to mitigate this vulnerability.

Ust-Polui: bone objects with ornament and signs (technology and function)

The article is devoted to the studies of the function of bone artefacts with ornamentation and signs from the Ust-Polui sacral production center. Functional groups of items with and without décor were identified and compared to each other according to the use-wear pattern. The main elements and compositions of the decorations that are typical for the certain categories were studied. The location and ways of ornamentation and signs were analyzed. It was shown that buckles, combs and armored plates make up the largest percentage of ornamentally decorated items, while signs are often applied to scrapers-blades. Fish knives, hooks, chisel-shaped tools, wedges, needles, harpoons and arrowheads except two of them have no decoration elements. The oblique cuts and small notches on the edges of several items made of the reindeer harness apparently were technologically meaningful. The bone products of the Ust-Polui are characterized by geometric ornaments with a small set of elements and their combinations. A pattern consisting of one or more wavy lines, made using the technique of fine-contour or oval-notched carving, was a common decorative element for functionally various items. It was complemented by compositions of straight or broken lines. There is no correlation between degree of wear and the presence or absence of decor in tools of the same category. Armor plates, buckles, combs, scrapers-spatulas had most strong wear traces among the specimens with ornamentation. Geometric signs were found on a bow plate, 2 belt hooks, 3 spoons and 14 scrapers-spatulas. They have a different carving quality and shape. There were often 2 signs carved on the items; some signs were applied to the surface of the scrapers after their long-term use.

Análisis de sistemas mecánicos utilizando sistemas CAE, para estudiantes de ingeniería mecatrónica

This work shows that the fundamentals of CAE computeraided engineering systems can be used as an effective tool for optimizing the analysis of mechanical systems and / or manufacturing processes in mechatronic engineering subjects. The simulation of operating conditions, as well as the analysis of different working conditions such as stress analysis, thermal analysis, process optimization and product optimization, allows the CAE tool to be used in a wide variety of processes from previous designs to digitization of reverse engineering processes. During the development of technological skills as mechatronic engineers, CAE tools are essential for students to simulate processes and operating conditions that integrate manufacturing machines or cells. Given the wide variety of tools, CAE techniques can be developed by different methods, however in this case, finite element analysis (FEA) will be used, as a numerical resolution technique that considers that any component can be particularized, in a set of small elements with simple geometry and known physical behavior, this method is generally applied to different engineering fields.

A Subspace Method for Fast Locally Injective Harmonic Mapping

AbstractWe present a fast algorithm for low‐distortion locally injective harmonic mappings of genus 0 triangle meshes with and without cone singularities. The algorithm consists of two portions, a linear subspace analysis and construction, and a nonlinear non‐convex optimization for determination of a mapping within the reduced subspace. The subspace is the space of solutions to the Harmonic Global Parametrization (HGP) linear system [BCW17], and only vertex positions near cones are utilized, decoupling the variable count from the mesh density. A key insight shows how to construct the linear subspace at a cost comparable to that of a linear solve, extracting a very small set of elements from the inverse of the matrix without explicitly calculating it. With a variable count on the order of the number of cones, a tangential alternating projection method [HCW17] and a subsequent Newton optimization [CW17] are used to quickly find a low‐distortion locally injective mapping. This mapping determination is typically much faster than the subspace construction. Experiments demonstrating its speed and efficacy are shown, and we find it to be an order of magnitude faster than HGP and other alternatives.

Trapping molecules for quantum chemistry

The Search and Discovery piece by Ashley Smart in the April 2017 issue of Physics Today (page 18) reported the excellent work on magnetic stopping and trapping of methyl radicals by the group of Takamasa Momose (University of British Columbia). I am writing to provide a different perspective on the field than what was conveyed by the author. The very first sentence of Smart’s article brings up a whole discussion: “By and large, physicists have succeeded in their quest to tame the atom.”The past few decades have seen remarkable advances in the ability to control and cool atoms in the gas phase. Those advances have been enabled by laser-cooling, which produces ultracold atomic gases. The atoms are then further cooled by evaporation to create quantum degenerate gases. However, those methods are far from ideal, even for atoms.Laser cooling is not a general method. Due to the requirements of a cycling transition and available lasers, it works on only a small set of elements in the periodic table. Evaporative cooling requires the right balance between elastic and inelastic collisions, again severely limiting generality. Furthermore, evaporative cooling leads to a large loss of atoms. For the alkalis, the optimum cases for laser cooling and evaporative cooling, the flux of ultracold atoms has been limited by optical density to around 109 atoms per second.It is natural to ask whether one can invent new methods that work on most elements and that break the current limit on flux. Such a development would open many new possibilities for fundamental science and for real-life applications. The challenges and limitations have motivated several groups to explore alternative approaches. One method is buffer-gas cooling, pioneered by John Doyle at Harvard University.11. J. M. Doyle et al., Phys. Rev. A 52, R2515 (1995). https://doi.org/10.1103/PhysRevA.52.R2515 A different approach was developed independently and in parallel by Frédéric Merkt and his group at ETH Zürich and by my group at the University of Texas at Austin: magnetic stopping and trapping of paramagnetic atoms in a supersonic beam.22. S. D. Hogan et al., Phys. Rev. Lett. 101, 143001 (2008). https://doi.org/10.1103/PhysRevLett.101.143001,33. E. Narevicius et al., Phys. Rev. Lett. 100, 093003 (2008). https://doi.org/10.1103/PhysRevLett.100.093003 That work was summarized in an invited review article I wrote for Science.44. M. G. Raizen, Science 324, 1403 (2009). https://doi.org/10.1126/science.1171506 Since then, many new developments have continued to advance the field.Now that the first sentence of the Search and Discovery piece is out of the way, I can discuss the rest—in particular, the motivation of studying quantum chemistry and the question of whether one actually needs to trap molecules. The goal of studying chemical reactions at ultralow temperatures is to observe unique quantum pathways that can dominate the reaction dynamics. Until recently it has been an elusive goal. Stopping and trapping molecules, either by electrostatic or magnetic forces, has produced a phase-space density that is too low for the study of chemical reactions. Molecules at much higher phase-space density can be produced by starting with Bose–Einstein condensates and “making” molecules with lasers. However, those experiments have so far been limited to alkali chemistry.Work by the Narevicius group at the Weizmann Institute of Science in Israel provided a major breakthrough in quantum chemistry without the need for stopping and trapping. Their approach relies on the merging of two supersonic beams by magnetically deflecting one of them.55. A. B. Henson et al., Science 338, 234 (2012). https://doi.org/10.1126/science.1229141 The copropagating beams have controllable collision energies down to temperatures of several millikelvin. The resulting chemical reactions, observed as a function of energy, reveal striking quantum resonances in the reaction dynamics. That work is continuing, and it demonstrates the power of merged beams, which do not require trapping and cooling. To study slower chemical reactions, trapping at high phase-space density is necessary. New ideas and work along those lines are in progress and will hopefully prove successful.ReferencesSection:ChooseTop of pageReferences <<CITING ARTICLES1. J. M. Doyle et al., Phys. Rev. A 52, R2515 (1995). https://doi.org/10.1103/PhysRevA.52.R2515, Google ScholarCrossref, ISI2. S. D. Hogan et al., Phys. Rev. Lett. 101, 143001 (2008). https://doi.org/10.1103/PhysRevLett.101.143001, Google ScholarCrossref3. E. Narevicius et al., Phys. Rev. Lett. 100, 093003 (2008). https://doi.org/10.1103/PhysRevLett.100.093003, Google ScholarCrossref, ISI4. M. G. Raizen, Science 324, 1403 (2009). https://doi.org/10.1126/science.1171506, Google ScholarCrossref5. A. B. Henson et al., Science 338, 234 (2012). https://doi.org/10.1126/science.1229141, Google ScholarCrossref, ISI© 2017 American Institute of Physics.

SCCharts: sequentially constructive statecharts for safety-critical applications

We present a new visual language, SCCharts , designed for specifying safety-critical reactive systems. SCCharts use a statechart notation and provide determinate concurrency based on a synchronous model of computation (MoC), without restrictions common to previous synchronous MoCs. Specifically, we lift earlier limitations on sequential accesses to shared variables, by leveraging the sequentially constructive MoC. The semantics and key features of SCCharts are defined by a very small set of elements, the Core SCCharts , consisting of state machines plus fork/join concurrency. We also present a compilation chain that allows efficient synthesis of software and hardware.

Quarry identification of historical building materials by means of laser induced breakdown spectroscopy, X-ray fluorescence and chemometric analysis

To characterize historical building materials according to the geographic origin of the quarries from which they have been mined, the relative content of major and trace elements were determined by means of Laser Induced Breakdown Spectroscopy (LIBS) and X-ray Fluorescence (XRF) techniques. 48 different specimens were studied and the entire samples' set was divided in two different groups: the first, used as reference set, was composed by samples mined from eight different quarries located in Seville province; the second group was composed by specimens of unknown provenance collected in several historical buildings and churches in the city of Seville. Data reduction and analysis on laser induced breakdown spectroscopy and X-ray fluorescence measurements was performed using multivariate statistical approach, namely the Linear Discriminant Analysis (LDA), Principal Component Analysis (PCA) and Soft Independent Modeling of Class Analogy (SIMCA). A clear separation among reference sample materials mined from different quarries was observed in Principal Components (PC) score plots, then a supervised soft independent modeling of class analogy classification was trained and run, aiming to assess the provenance of unknown samples according to their elemental content. The obtained results were compared with the provenance assignments made on the basis of petrographical description. This work gives experimental evidence that laser induced breakdown spectroscopy measurements on a relatively small set of elements is a fast and effective method for the purpose of origin identification.

Drosophila as a focus in olfactory research: mapping of olfactory sensilla by fine structure, odor specificity, odorant receptor expression, and central connectivity.

This review intends to integrate recent data from the Drosophila olfactory system into an up-to-date account of the neuronal basis of olfaction. It focuses on (1) an electron microscopic study that mapped a large proportion of fruitfly olfactory sensilla, (2) large-scale electrophysiological recordings that allowed the classification of the odor response spectra of a complete set of sensilla, (3) the identification and expression patterns of candidate odorant receptors in the olfactory tissues, (4) central projections of neurons expressing a given odorant receptor, (5) an improved glomerular map of the olfactory center, and (6) attempts to exploit the larval olfactory system as a model of reduced cellular complexity. These studies find surprising parallels between the olfactory systems of flies and mammals, and thus underline the usefulness of the fruitfly as an olfactory model system. Both in Drosophila and in mammals, odorant receptor neurons appear to express only one type of receptor. Neurons expressing a given receptor are scattered in the olfactory tissues but their afferents converge onto a few target glomeruli only. This suggests that in both phyla, the periphery is represented in the brain as a chemotopic map. The major difference between mammals and fruitflies refers to the numbers of receptors, neurons, and glomeruli, which are largely reduced in the latter, and particularly in larvae. Yet, if activated in a combinatorial fashion, even this small set of elements could allow discrimination between a vast array of odorants.

Can young children integrate premises in transitivity and serial order tasks?

An analysis is presented of the relational information needed for premise integration in transitivity and simple serial order tasks. The tasks are divided into those where an ordering decision can be made by considering a single binary relation, and those where two binary relations must be considered. Four experiments are reported, the principal purpose of which is to manipulate the number of relations which must be considered in making decisions about the order of a small set of elements. In every test it was found that preschool children succeeded if decisions could be made by considering one relation, but failed if two relations had to be considered. Children over 5 almost always succeeded in both cases. It is concluded that preschool children cannot integrate relational premise information, and therefore cannot understand transitivity or serial order. This would impose limitations on their understanding of quantification and a number of other concepts. It is also suggested that the amount of information required to make a single decision may be an important factor determining cognitive complexity generally.