Results for "Elefteris Ioannou"

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Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavitiesMay 14 2019Two-dimensional, meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors ... More
Perturbative renormalization in parton distribution functions using improved actionsDec 27 2005We calculate the 1-loop renormalization of a set of extended fermionic bilinears which form a basis corresponding to moments of the parton distribution functions. We use the overlap action for fermions and Luescher-Weisz (LW) action for gluons. Our results ... More
Perturbative renormalization in parton distribution functions using Overlap fermions and Symanzik improved gluonsJan 17 2006Mar 02 2006We calculate the 1-loop renormalization of the fermion self-energy, all local fermion bilinears, as well as a set of extended bilinears which form a basis corresponding to moments of the parton distribution functions. We use the overlap action for fermions ... More
Unconditionally-secure and reusable public-key authenticationAug 14 2011We present a quantum-public-key identification protocol and show that it is secure against a computationally-unbounded adversary. This demonstrates for the first time that unconditionally-secure and reusable public-key authentication is possible in principle ... More
Limitations of some simple adiabatic quantum algorithmsFeb 26 2007Jun 02 2008Let $H(t)=(1-t/T)H_0 + (t/T)H_1$, $t\in [0,T]$, be the Hamiltonian governing an adiabatic quantum algorithm, where $H_0$ is diagonal in the Hadamard basis and $H_1$ is diagonal in the computational basis. We prove that $H_0$ and $H_1$ must each have at ... More
A new spin on quantum cryptography: Avoiding trapdoors and embracing public keysSep 15 2011We give new arguments in support of \emph{signed quantum key establishment}, where quantum cryptography is used in a public-key infrastructure that provides the required authentication. We also analyze more thoroughly than previous works the benefits ... More
Universal quantum computation in a hidden basisOct 15 2008Aug 19 2010Let $\ket{\0}$ and $\ket{\1}$ be two states that are promised to come from known subsets of orthogonal subspaces, but are otherwise unknown. Our paper probes the question of what can be achieved with respect to the basis $\{\ket{\0},\ket{\1}}^{\otimes ... More
Public-key cryptography based on bounded quantum reference framesMar 30 2009Aug 14 2011We demonstrate that the framework of bounded quantum reference frames has application to building quantum-public-key cryptographic protocols and proving their security. Thus, the framework we introduce can be seen as a public-key analogue of the framework ... More
Statistical State Dynamics: a new perspective on turbulence in shear flowDec 29 2014Traditionally, single realizations of the turbulent state have been the object of study in shear flow turbulence. When a statistical quantity was needed it was obtained from a spatial, temporal or ensemble average of sample realizations of the turbulence. ... More
A theory for the emergence of coherent structures in beta-plane turbulenceMar 26 2013Oct 10 2013Planetary turbulent flows are observed to self-organize into large scale structures such as zonal jets and coherent vortices. One of the simplest models of planetary turbulence is obtained by considering a barotropic flow on a beta-plane channel with ... More
Compound Outage Probability and Capacity of a Class of Fading MIMO Channels with Channel Distribution UncertaintyFeb 05 2011Outage probability and capacity of a class of block-fading MIMO channels are considered with partial channel distribution information. Specifically, the channel or its distribution are not known but the latter is known to belong to a class of distributions ... More
Structure and mechanism in a second-order statistical state dynamics model of self-sustaining turbulence in plane Couette flowJul 18 2016This paper describes a study of the self-sustaining process (SSP) that maintains turbulence in wall-bounded shear flow. The study uses Couette flow and is based on a statistical state dynamics (SSD) model closed at second order with state variables the ... More
A statistical state dynamics based theory for the formation and equilibration of Saturn's North Polar JetSep 20 2016Coherent jets containing most of the kinetic energy of the flow are a common feature in observations of atmospheric turbulence. In the gaseous planets these jets are maintained by incoherent turbulence excited by small scale convection. Large scale coherent ... More
Optimal excitation of two dimensional Holmboe instabilitiesNov 01 2010Apr 20 2011Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified ... More
Fourier-Resolved Spectroscopy of AGN using XMM-Newton data: I. The 3-10 keV band resultsJan 29 2007We present the results from the Fourier Resolved Spectroscopy of archival XMM-Newton data of five AGN, namely, Mrk 766, NGC 3516, NGC 3783, NGC 4051 and Ark 564. This work supplements the earlier study of MCG-6-30-15 as well as those of several Galactic ... More
Deterministic quantum-public-key encryption: forward search attack and randomizationMar 27 2009In the classical setting, public-key encryption requires randomness in order to be secure against a forward search attack, whereby an adversary compares the encryption of a guess of the secret message with that of the actual secret message. We show that ... More
Emergence of non-zonal coherent structuresJan 21 2015Planetary turbulence is observed to self-organize into large-scale structures such as zonal jets and coherent vortices. One of the simplest models that retains the relevant dynamics of turbulent self-organization is a barotropic flow in a beta-plane channel ... More
Stochastic Structural Stability Theory applied to roll/streak formation in boundary layer shear flowNov 05 2010Stochastic Structural Stability Theory (SSST) provides an autonomous, deterministic, nonlinear dynamical system for evolving the statistical mean state of a turbulent system. In this work SSST is applied to the problem of understanding the formation of ... More
Elevating commodity storage with the SALSA host translation layerJan 17 2018Jan 10 2019To satisfy increasing storage demands in both capacity and performance, industry has turned to multiple storage technologies, including Flash SSDs and SMR disks. These devices employ a translation layer that conceals the idiosyncrasies of their mediums ... More
How much randomness can be generated from a quantum black-box device?Nov 06 2018Nov 20 2018Quantum theory allows for randomness generation in a device-independent setting, where no detailed description of the experimental device is required. Here we derive a general upper bound on the amount of randomness that can be generated in such a setting. ... More
Drift wave-zonal flow dynamicsAug 07 2009A remarkable phenomenon in turbulent flows is the spontaneous emergence of coherent large spatial scale zonal jets. Geophysical examples of this phenomenon include the Jovian banded winds and the Earth's polar front jet. In this work a comprehensive theory ... More
Emergence of large scale structure in planetary turbulenceNov 28 2012Mar 05 2013Planetary and magnetohydrodynamic drift-wave turbulence is observed to self-organize into large scale structures such as zonal jets and coherent vortices. In this Letter we present a non-equilibrium statistical theory, the Stochastic Structural Stability ... More
Instability of the roll/streak structure induced by free-stream turbulence in pre-transitional Couette flowJul 18 2016Although the roll/streak structure is ubiquitous in pre-transitional wall-bounded shear flow, this structure is linearly stable if the idealization of laminar flow is made. Lacking an instability, the large transient growth of the roll/streak structure ... More
A new mass-ratio for the X-ray Binary X2127+119 in M15?Jun 25 2004The luminous low-mass X-ray binary X2127+119 in the core of the globular cluster M15 (NGC 7078), which has an orbital period of 17 hours, has long been assumed to contain a donor star evolving off the main sequence, with a mass of 0.8 solar masses (the ... More
The X-ray variability and the near-IR to X-ray spectral energy distribution of four low luminosity Seyfert 1 galaxiesSep 10 2008We present the results from a study of the X-ray variability and the near-IR to X-ray spectral energy distribution of four low-luminosity, Seyfert 1 galaxies. We compared their variability amplitude and broad band spectrum with those of more luminous ... More
Refining Architectures of Deep Convolutional Neural NetworksApr 22 2016Deep Convolutional Neural Networks (CNNs) have recently evinced immense success for various image recognition tasks. However, a question of paramount importance is somewhat unanswered in deep learning research - is the selected CNN optimal for the dataset ... More
Deep Roots: Improving CNN Efficiency with Hierarchical Filter GroupsMay 20 2016We propose a new method for training computationally efficient and compact convolutional neural networks (CNNs) using a novel sparse connection structure that resembles a tree root. Our sparse connection structure facilitates a significant reduction in ... More
Mass Outflow from the X-ray Binary X2127+119 in M15Jul 18 2002The bright X-ray binary X2127+119 in the core of the globular cluster M15 has long been thought to be in an unusual evolutionary state, in which the binary is embedded in a common envelope. Support for this idea comes from X2127+119's absorption lines, ... More
Parallel training of linear models without compromising convergenceNov 05 2018Dec 19 2018In this paper we analyze, evaluate, and improve the performance of training generalized linear models on modern CPUs. We start with a state-of-the-art asynchronous parallel training algorithm, identify system-level performance bottlenecks, and apply optimizations ... More
Training CNNs with Low-Rank Filters for Efficient Image ClassificationNov 20 2015Feb 07 2016We propose a new method for creating computationally efficient convolutional neural networks (CNNs) by using low-rank representations of convolutional filters. Rather than approximating filters in previously-trained networks with more efficient versions, ... More
S3T stability of the homogeneous state of barotropic beta-plane turbulenceJul 12 2014Nov 24 2014Zonal jets and non-zonal large-scale flows are often present in forced-dissipative barotropic turbulence on a beta-plane. The dynamics underlying the formation of both zonal and non-zonal coherent structures is investigated in this work within the statistical ... More
Difference of Normals as a Multi-Scale Operator in Unorganized Point CloudsSep 08 2012A novel multi-scale operator for unorganized 3D point clouds is introduced. The Difference of Normals (DoN) provides a computationally efficient, multi-scale approach to processing large unorganized 3D point clouds. The application of DoN in the multi-scale ... More
A statistical state dynamics approach to wall-turbulenceSep 21 2016This paper reviews results demonstrating the benefits of studying wall-bounded shear flows using dynamics for the evolution of the statistical state of the turbulent system. The statistical state dynamics (SSD) approach used in this work employs a second ... More
Statistical state dynamics of weak jets in barotropic beta-plane turbulenceAug 09 2017Nov 01 2018Zonal jets in a barotropic setup emerge out of homogeneous turbulence through a flow-forming instability of the homogeneous turbulent state (`zonostrophic instability') which occurs as the turbulence intensity increases. This has been demonstrated using ... More
Detonation propagation in annular arcs of condensed phase explosivesOct 20 2017Nov 20 2017We present a numerical study of detonation propagation in unconfined explosive charges shaped as an annular arc (rib). Steady detonation in a straight charge propagates at constant speed but when it enters an annular section, it goes through a transition ... More
Convex Separation from Optimization via HeuristicsMar 22 2006Let $K$ be a full-dimensional convex subset of $\mathbb{R}^n$. We describe a new polynomial-time Turing reduction from the weak separation problem for $K$ to the weak optimization problem for $K$ that is based on a geometric heuristic. We compare our ... More
Statistical state dynamics of jet/wave coexistence in barotropic beta-plane turbulenceSep 21 2015Mar 03 2016Jets coexist with planetary scale waves in the turbulence of planetary atmospheres. The coherent component of these structures arises from cooperative interaction between the coherent structures and the incoherent small-scale turbulence in which they ... More
Emergence and equilibration of jets in beta-plane turbulence: applications of Stochastic Structural Stability TheoryAug 28 2012Nov 10 2013Stochastic Structural Stability Theory (S3T) provides analytical methods for understanding the emergence and equilibration of jets from the turbulence in planetary atmospheres based on the dynamics of the statistical mean state of the turbulence closed ... More
Are cracked applications really free? An empirical analysis on Android devicesMar 12 2019Android is among the popular platforms running on millions of smart devices, like smartphones and tablets, whose widespread adoption is seen as an opportunity for spreading malware. Adding malicious payloads to cracked applications, often popular ones, ... More
Deep Roots: Improving CNN Efficiency with Hierarchical Filter GroupsMay 20 2016Nov 30 2016We propose a new method for creating computationally efficient and compact convolutional neural networks (CNNs) using a novel sparse connection structure that resembles a tree root. This allows a significant reduction in computational cost and number ... More
Measuring Neural Net Robustness with ConstraintsMay 24 2016Despite having high accuracy, neural nets have been shown to be susceptible to adversarial examples, where a small perturbation to an input can cause it to become mislabeled. We propose metrics for measuring the robustness of a neural net and devise a ... More
Measuring Neural Net Robustness with ConstraintsMay 24 2016Jun 16 2017Despite having high accuracy, neural nets have been shown to be susceptible to adversarial examples, where a small perturbation to an input can cause it to become mislabeled. We propose metrics for measuring the robustness of a neural net and devise a ... More
Decision Forests, Convolutional Networks and the Models in-BetweenMar 03 2016This paper investigates the connections between two state of the art classifiers: decision forests (DFs, including decision jungles) and convolutional neural networks (CNNs). Decision forests are computationally efficient thanks to their conditional computation ... More
Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavitiesMay 14 2019May 15 2019Two-dimensional, meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors ... More
Self-sustaining turbulence in a restricted nonlinear model of plane Couette flowFeb 20 2014This paper demonstrates the maintenance of self-sustaining turbulence in a restricted nonlinear (RNL) model of plane Couette flow. The RNL system is derived directly from the Navier Stokes equations and permits computationally tractable studies of the ... More
Improved algorithm for quantum separability and entanglement detectionMar 04 2004Jul 15 2005Determining whether a quantum state is separable or entangled is a problem of fundamental importance in quantum information science. It has recently been shown that this problem is NP-hard. There is a highly inefficient `basic algorithm' for solving the ... More
Hardness and Ease of Curing the Sign Problem for Two-Local Qubit HamiltoniansJun 20 2019We examine the problem of determining whether a multi-qubit two-local Hamiltonian can be made stoquastic by single-qubit unitary transformations. We prove that when such a Hamiltonian contains one-local terms, then this task can be NP-hard. This is shown ... More
A minimal model of self-sustaining turbulenceJan 10 2015In this work we examine the turbulence maintained in a Restricted Nonlinear (RNL) model of plane Couette flow. This model is a computationally efficient approximation of the second order statistical state dynamics (SSD) obtained by partitioning the flow ... More
A TiO study of the black-hole binary GRO J0422+32 in a very low stateApr 17 2000We present 53 simultaneous photometric (I band) and spectroscopic (6900-9500 Angstroms) observations of J0422+32, taken during December 1997. From these we determine that J0422+32 was in its lowest state yet observed, at I=20.44+/-0.08. Using relative ... More
Snap ML: A Hierarchical Framework for Machine LearningMar 16 2018Nov 29 2018We describe a new software framework for fast training of generalized linear models. The framework, named Snap Machine Learning (Snap ML), combines recent advances in machine learning systems and algorithms in a nested manner to reflect the hierarchical ... More
Motional Sideband Asymmetry in Quantum Optomechanics in the Presence of Kerr-type NonlinearitiesMay 31 2018Jun 01 2018Asymmetry in the motional sideband spectrum is a signature of the quantum regime of mechanical oscillators. It enables self-calibrated thermometry measurements, and has recently been experimentally studied in several optomechanical systems. Here, we present ... More
The ``Outside-In'' Outburst of HT CassiopeiaeJul 12 1999We present results from photometric observations of the dwarf nova system HT Cas during the eruption of November 1995. The data include the first two--colour observations of an eclipse on the rise to outburst. They show that during the rise to outburst ... More
Understanding the LMXB X2127+119 in M15 I. X-ray eclipses and dipsNov 13 2001We present X-ray observations of the high-inclination low-mass X-ray binary system X2127+119 (AC211) in the globular cluster M15 (NGC 7078). The observations consist of data acquired in 1996 with the RXTE satellite and in 1995 with the ASCA satellite. ... More
Understanding the LMXB X2127+119 in M15Dec 05 2002We present HST UV observations of the high-inclination low mass X-ray binary AC211 (X2127+119), which is located in the globular cluster M15 (NGC 7078). We have discovered a CIV P Cygni profile in this system, which confirms the existence of an outflow ... More
Nonreciprocal reconfigurable microwave optomechanical circuitDec 24 2016Jun 01 2017Devices that achieve nonreciprocal microwave transmission are ubiquitous in radar and radio-frequency communication systems, and commonly rely on magnetically biased ferrite materials. Such devices are also indispensable in the readout chains of superconducting ... More
A statistical state dynamics based study of the structure and mechanism of large-scale motions in plane Poiseuille flowDec 18 2015Sep 29 2016The perspective of statistical state dynamics (SSD) has recently been applied to the study of mechanisms underlying turbulence in various physical systems. An example implementation of SSD is the second order closure referred to as stochastic structural ... More
Turbulence in the highly restricted dynamics of a closure at second order: comparison with DNSJan 30 2014S3T (Stochastic Structural Stability Theory) employs a closure at second order to obtain the dynamics of the statistical mean turbulent state. When S3T is implemented as a coupled set of equations for the streamwise mean and perturbation states, nonlinearity ... More
A statistical state dynamics-based study of the structure and mechanism of large-scale motions in plane Poiseuille flowDec 18 2015Nov 14 2016The perspective of statistical state dynamics (SSD) has recently been applied to the study of mechanisms underlying turbulence in various physical systems. An example implementation of SSD is the second order closure referred to as stochastic structural ... More
Scientific Domain Knowledge Improves Exoplanet Transit Classification with Deep LearningOct 31 2018Nov 21 2018Space-based missions such as Kepler, and soon TESS, provide large datasets that must be analyzed efficiently and systematically. Recent work by Shallue & Vanderburg (2018) successfully used state-of-the-art deep learning models to automatically classify ... More
Rapid Classification of TESS Planet Candidates with Convolutional Neural NetworksFeb 22 2019Accurately and rapidly classifying exoplanet candidates from transit surveys is a goal of growing importance as the data rates from space-based survey missions increases. This is especially true for NASA's TESS mission which generates thousands of new ... More
A Spatially Resolved `Inside-out' Outburst of IP PegasiJul 12 1999We present a comprehensive photometric dataset taken over the entire outburst of the eclipsing dwarf nova IP Peg in September/October 1997. Analysis of the lightcurves taken over the long rise to the peak-of-outburst shows conclusively that the outburst ... More
FPGA-based Multi-Chip Module for High-Performance ComputingJun 26 2019Current integration, architectural design and manufacturing technologies are not suited for the computing density and power efficiency requested by Exascale computing. New approaches in hardware architecture are thus needed to overcome the technological ... More
Search for TeV $γ$-ray emission from AE Aqr coincident with high optical and X-ray states with the MAGIC telescopesSep 10 2013We report on observations of the nova-like cataclysmic variable AE Aqr performed by MAGIC. The observations were part of a quasi-simultaneous multi-wavelength campaign carried out between 2012 May and June covering the optical, UV, X-ray and gamma-ray ... More
Multiwavelength Campaign of Observations of AE AqrNov 04 2011We provide a summary of results, obtained from a multiwavelength (TeV gamma-ray, X-ray, UV, optical, and radio) campaign of observations of AE Aqr conducted in 2005 August 28-September 2, on the nature and correlation of the flux variations in the various ... More
Multiwavelength observations revealing the outbursts of the two soft X-ray transients XTE J1859+226 and XTE J1118+480Feb 06 2001We report here on multiwavelength observations of the two new soft X-ray transients (SXTs) XTE J1859+226 and XTE J1118+480, which we observed with HST/RXTE/UKIRT. For XTE J1118+480 we also used EUVE since it is located at a very high galactic latitude ... More
A study of meson and baryon decays to strange final states with GlueX in Hall D (A proposal to the 39th Jefferson Lab Program Advisory Committee)Oct 16 2012The primary motivation of the GlueX experiment is to search for and ultimately study the pattern of gluonic excitations in the meson spectrum produced in gamma p collisions. Recent lattice QCD calculations predict a rich spectrum of hybrid mesons that ... More
An initial study of mesons and baryons containing strange quarks with GlueXMay 07 2013The primary motivation of the GlueX experiment is to search for and ultimately study the pattern of gluonic excitations in the meson spectrum produced in $\gamma p$ collisions. Recent lattice QCD calculations predict a rich spectrum of hybrid mesons that ... More
A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRCAug 01 2014We propose to enhance the kaon identification capabilities of the GlueX detector by constructing an FDIRC (Focusing Detection of Internally Reflected Cherenkov) detector utilizing the decommissioned BaBar DIRC components. The GlueX FDIRC would significantly ... More
MAGIC search for VHE $γ$-ray emission from AE Aquarii in a multiwavelength contextJul 14 2014It has been claimed that the nova-like cataclysmic variable (CV) AE Aquarii (AE Aqr) is a very-high-energy (VHE, $E>$100 GeV) source both on observational and theoretical grounds. We aim to search for VHE gamma-ray emission from AE Aqr during different ... More
Expected Performance of the ATLAS Experiment - Detector, Trigger and PhysicsDec 28 2008Aug 14 2009A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential ... More