Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- 2001 (6)
- 2005 (3)
- 2004 (2)
- 2006 (2)
- 2007 (2)
-
- 2008 (2)
- Broadcast algorithms (2)
- Distributed algorithms (2)
- Maximal ratio combiner (2)
- Routing (2)
- Simulations (2)
- Wireless ad hoc networks (2)
- 1996 (1)
- 1999 (1)
- 2002 (1)
- 2003 (1)
- Admission control (1)
- Bandwidth broker (1)
- Border Gateway Protocol (BGP) (1)
- Caching (1)
- Computer network security (1)
- Directional antennas (1)
- Dissipation (1)
- Dynamic scheduling (1)
- Early detection (1)
- Efficiency (1)
- Eigenanalysis (1)
- Empirical algorithmics (1)
- Export routing policies (1)
- Flow aggregation (1)
- Publication Year
- Publication
Articles 1 - 30 of 60
Full-Text Articles in Engineering
Performance Bounds For Grouped Incoherent Measurements In Compressive Sensing, Adam Polak, Marco Duarte, Dennis Goeckel
Performance Bounds For Grouped Incoherent Measurements In Compressive Sensing, Adam Polak, Marco Duarte, Dennis Goeckel
Marco Duarte
Compressive sensing (CS) allows for acquisition of sparse signals at sampling rates significantly lower than the Nyquist rate required for bandlimited signals. Recovery guarantees for CS are generally derived based on the assumption that measurement projections are selected independently at random. However, for many practical signal acquisition applications, including medical imaging and remote sensing, this assumption is violated as the projections must be taken in groups. In this paper, we consider such applications and derive requirements on the number of measurements needed for successful recovery of signals when groups of dependent projections are taken at random. We find a penalty …
Compressive Parameter Estimation Via Approximate Message Passing, Marco Duarte
Compressive Parameter Estimation Via Approximate Message Passing, Marco Duarte
Marco Duarte
No abstract provided.
Nanoimprint Lithography 20 Years On, Qiangfei Xia, R. Fabian Pease
Nanoimprint Lithography 20 Years On, Qiangfei Xia, R. Fabian Pease
Qiangfei Xia
To celebrate the 20th anniversary of nanoimprint lithography (NIL) we present a perspective of how the technique and its prospects have evolved over the past two decades. We describe how it overcame certain fabrication challenges at the time it was first reported and look at some of the obstacles that hindered uptake in industry initially, as well as likely sectors for future successful commercial deployment. Developments in the technique since that are making NIL increasingly attractive such as 'moving roll to roll' for higher throughput, are also described.
Nanoscale Memristive Radiofrequency Switches, Shuang Pi, Mohammad Ghadiri-Sadrabadi, Joseph C. Bardin, Qiangfei Xia
Nanoscale Memristive Radiofrequency Switches, Shuang Pi, Mohammad Ghadiri-Sadrabadi, Joseph C. Bardin, Qiangfei Xia
Qiangfei Xia
Radiofrequency switches are critical components in wireless communication systems and consumer electronics. Emerging devices include switches based on microelectromechanical systems and phase-change materials. However, these devices suffer from disadvantages such as large physical dimensions and high actuation voltages. Here we propose and demonstrate a nanoscale radiofrequency switch based on a memristive device. The device can be programmed with a voltage as low as 0.4 V and has an ON/OFF conductance ratio up to 1012 with long state retention. We measure the radiofrequency performance of the switch up to 110 GHz and demonstrate low insertion loss (0.3 dB at 40 GHz), …
General Properties For Determining Power Loss And Efficiency Of Passive Multi-Port Microwave Networks, Ramakrishna Janaswamy
General Properties For Determining Power Loss And Efficiency Of Passive Multi-Port Microwave Networks, Ramakrishna Janaswamy
Ramakrishna Janaswamy
Starting from the scattering matrix formulation, three useful properties are derived that characterize the dissipative loss and the corresponding efficiency of a multiport, passive microwave network. Elementary examples are considered that involve both reciprocal and non-reciprocal networks to demonstrate the utility of the expressions provided. When applied to the equal-split, matched, 3-port resistive divider, they recover the known fact that the device is 50% efficient. The relations yield the new result that the efficiency of a 3-port Wilkinson power divider is 2/3 on the average. Using the results presented it is further shown that the Wilkinson power divider belongs to …
Masking Schemes For Image Manifolds, Hamid Dadkhahi, Marco Duarte
Masking Schemes For Image Manifolds, Hamid Dadkhahi, Marco Duarte
Marco Duarte
We consider the problem of selecting an optimal mask for an image manifold, i.e., choosing a subset of the dimensions of the image space that preserves the manifold structure present in the original data. Such masking implements a form of compressed sensing that reduces power consumption in emerging imaging sensor platforms. Our goal is for the manifold learned from masked images to resemble the manifold learned from full images as closely as possible. We show that the process of finding the optimal masking pattern can be cast as a binary integer program, which is computationally expensive but can be approximated …
Complexity-Adaptive Universal Signal Estimation For Compressed Sensing, Junan Zhu, Dror Baron, Marco Duarte
Complexity-Adaptive Universal Signal Estimation For Compressed Sensing, Junan Zhu, Dror Baron, Marco Duarte
Marco Duarte
We study the compressed sensing (CS) signal estimation problem where a signal is measured via a linear matrix multiplication under additive noise. While this setup usually assumes sparsity or compressibility in the signal during estimation, additional signal structure that can be leveraged is often not known a priori. For signals with independent and identically distributed (i.i.d.) entries, existing CS algorithms achieve optimal or near optimal estimation error without knowing the statistics of the signal. This paper addresses estimating stationary ergodic non-i.i.d. signals with unknown statistics. We have previously proposed a universal CS approach to simultaneously estimate the statistics of a …
Concentric Rings Of Polystyrene And Titanium Dioxide Nanoparticles Patterned By Alternating Current Signal Guided Coffee Ring Effect, Jinhua Mu, Peng Lin, Qiangfei Xia
Concentric Rings Of Polystyrene And Titanium Dioxide Nanoparticles Patterned By Alternating Current Signal Guided Coffee Ring Effect, Jinhua Mu, Peng Lin, Qiangfei Xia
Qiangfei Xia
The authors studied the surface deposition of nanoparticles by introducing an alternating current (AC) signal into the millimeter-sized nanoparticle droplet. For both polystyrene (PS) in deionized (DI) water and titanium dioxide (TiO2) in toluene, the nanoparticles self-assembled into regular concentric rings over a larger area on the substrate during the droplet drying process. The patterned area decreased, and the inter-ring spacing increased with higher AC frequencies for the TiO2/toluene system, while those for the PS/DI water system only changed slightly. The frequency dependent pattern formation was interpreted by the interaction between different factors such as capillary flow and the AC …
Single- And Bi-Layer Memristive Devices With Tunable Properties Using Tiox Switching Layers Deposited By Reactive Sputtering, Hao Jiang, Qiangfei Xia
Single- And Bi-Layer Memristive Devices With Tunable Properties Using Tiox Switching Layers Deposited By Reactive Sputtering, Hao Jiang, Qiangfei Xia
Qiangfei Xia
The authors systematically studied reactive sputtering deposition of TiOx thin films using a mixture of Ar and O2 gases under different ratios of O2 flow. As directly revealed by X-ray photoelectron spectroscopy, the deposition changed from a metallic Ti target mode to an oxide target mode when the O2 flow ratio was beyond 40%, resulting in TiOx thin films with different chemical compositions. Consequently, metal/oxide/metal devices with a single TiOx layer exhibited a broad spectrum of electrical characteristics such as Ohmic, rectifying, and memristive behavior. The reactive sputtering deposited TiOx thin films were also used in a bilayer memristive device …
3d Integration Of Planar Crossbar Memristive Devices With Cmos Substrate, Peng Lin, Shuang Pi, Qiangfei Xia
3d Integration Of Planar Crossbar Memristive Devices With Cmos Substrate, Peng Lin, Shuang Pi, Qiangfei Xia
Qiangfei Xia
Memristive devices are promising building blocks for enhanced CMOS hardware in data storage and computing. Nanoimprint lithography (NIL) has been an enabling technology in the past decade for exploring novel devices and circuits. In this paper, the authors review the progress and technical aspects of the fabrication and integration of memristor crossbar arrays using NIL. Since the key component of successful fabrication is the imprint mold, the material selection, master mold fabrication, anti-sticking treatment and cleaning are first discussed. The requirements and composition of imprint resists, in particular low-viscosity liquid resists that cross-link upon ultraviolet light radiation, are investigated next. …
Direct Solution Of Current Density Induced On A Rough Surface By Forward Propagating Waves, Ramakrishna Janaswamy
Direct Solution Of Current Density Induced On A Rough Surface By Forward Propagating Waves, Ramakrishna Janaswamy
Ramakrishna Janaswamy
A new Volterra integral equation of the second kind with square integrable kernel is derived for paraxial propagation of radiowaves over a gently varying, perfectly conducting rough surface. The integral equation is solved exactly in terms of a infinite series and the necessary and sufficient conditions for the solution to exist and converge are established. Super exponential convergence of the Neumann series for arbitrary surface slope is established through asymptotic analysis. Expressions are derived for the determination of the number of terms needed to achieve a given accuracy, the latter depending on the parameters of the rough surface, the frequency …
Effect Of Voltage Polarity And Amplitude On Electroforming Of Tio2 Based Memristive Devices, Hao Jiang, Qiangfei Xia
Effect Of Voltage Polarity And Amplitude On Electroforming Of Tio2 Based Memristive Devices, Hao Jiang, Qiangfei Xia
Qiangfei Xia
Pt/TiO2/Pt/Ti memristive devices were electrically formed to either the ON or OFF state using voltages of the same polarity but with different amplitudes. The forming step dictated the subsequent switching behaviour. A qualitative model based on the creation and migration of oxygen vacancies was proposed to explain the experimental results.
Effect Of Voltage Polarity And Amplitude On Electroforming Of Tio2 Based Memristive Devices, Hao Jiang, Qiangfei Xia
Effect Of Voltage Polarity And Amplitude On Electroforming Of Tio2 Based Memristive Devices, Hao Jiang, Qiangfei Xia
Qiangfei Xia
Pt/TiO2/Pt/Ti memristive devices were electrically formed to either the ON or OFF state using voltages of the same polarity but with different amplitudes. The forming step dictated the subsequent switching behaviour. A qualitative model based on the creation and migration of oxygen vacancies was proposed to explain the experimental results.
Cross Point Arrays Of 8 Nm × 8 Nm Memristive Devices Fabricated With Nanoimprint Lithography, Shuang Pi, Peng Lin, Qiangfei Xia
Cross Point Arrays Of 8 Nm × 8 Nm Memristive Devices Fabricated With Nanoimprint Lithography, Shuang Pi, Peng Lin, Qiangfei Xia
Qiangfei Xia
Building arrays of memristive devices with sub-10 nm lateral dimensions is critical for high packing density, low power consumption, and better uniformity in device performance. Here, the authors demonstrate arrays of 8 × 8 nm2 cross point memristive devices using wet chemical etching and nanoimprint lithography. The devices exhibited nonvolatile bipolar switching with extreme low programming current of 600 pA. The devices also exhibited fast switching speed and improved uniformity and promising endurance and data retention. This work opens the opportunities for memristive devices in the next generation ultrahigh-density data storage and low-power high-speed unconventional computing.
Low Voltage Resistive Switching Devices Based On Chemically Produced Silicon Oxide, Can Li, Hao Jiang, Qiangfei Xia
Low Voltage Resistive Switching Devices Based On Chemically Produced Silicon Oxide, Can Li, Hao Jiang, Qiangfei Xia
Qiangfei Xia
We developed nonvolatile metal/SiOx/Si memristive devices based on ultrathin (∼1 nm) silicon oxide that was produced in a Piranha solution. The devices exhibited repeatable resistive switching behavior with low programming voltages (as low as 0.5 V) and high ON/OFF conductance ratio. Devices with active metals as top electrodes were bipolar switches, while those with inert metal electrodes were unipolar. We also studied the switching mechanisms for both types of devices based on the filament formation and rupture, and proposed conduction models for Pt/SiOx/Si devices.
Mold Cleaning With Polydimethylsiloxane (Pdms) For Nanoimprint Lithography, Peng Lin, Shuang Pi, Jiang Jiang, Qiangfei Xia
Mold Cleaning With Polydimethylsiloxane (Pdms) For Nanoimprint Lithography, Peng Lin, Shuang Pi, Jiang Jiang, Qiangfei Xia
Qiangfei Xia
We present a simple and effective mold cleaning method for nanoimprint lithography. Polydimethylsiloxane (PDMS) prepolymer is spin-coated onto a contaminated imprint mold, thermally cured in an ambient environment, and then peeled off afterwards. Contaminants of 100 s μm to sub-50 nm sizes are effectively cleaned within one cycle. During the cleaning process, a very thin PDMS film (1–2 nm) is uniformly coated onto the mold surface, serving as a protection and anti-sticking layer.
The Effect Of Intellidrive On The Efficiency Of Highway Transportation Systems, Mohammad Nekoui, Hossein Pishro-Nik, Daiheng Ni
The Effect Of Intellidrive On The Efficiency Of Highway Transportation Systems, Mohammad Nekoui, Hossein Pishro-Nik, Daiheng Ni
Hossein Pishro-Nik
Recently, the IntelliDrive initiative has been proposed by the US Department of Transportation (USDOT) to enhance on-road safety and efficiency. In this study, we provide a mathematical framework which predicts the effect of such technologies on the efficiency of multilane highway systems prior to their real-life deployment. Our study shall encompass mixed traffic conditions in which a variety of assisted, automated and unequipped vehicles coexist. We show that intervehicular communications improves the flow of vehicles by reducing the perception-reaction (P-R) times of drivers and, in some cases, allowing for more efficient lane-changing operations. As we shall see, unlike the latter, …
Spectral-Based Propagation Schemes For Time-Dependent Quantum Systems With Applications To Carbon Nanotubes, Eric Polizzi, Zuojing Chen
Spectral-Based Propagation Schemes For Time-Dependent Quantum Systems With Applications To Carbon Nanotubes, Eric Polizzi, Zuojing Chen
Eric Polizzi
Effective modeling and numerical spectral-based propagation schemes are proposed for addressing the challenges in time-dependent quantum simulations of systems ranging from atoms, molecules, and nanostructures to emerging nanoelectronic devices. While time-dependent Hamiltonian problems can be formally solved by propagating the solutions along tiny simulation time steps, a direct numerical treatment is often considered too computationally demanding. In this paper, however, we propose to go beyond these limitations by introducing high-performance numerical propagation schemes to compute the solution of the time-ordered evolution operator. In addition to the direct Hamiltonian diagonalizations that can be efficiently performed using the new eigenvalue solver FEAST, …
Floornet: Deployment And Evaluation Of Amultihop Wireless 802.11 Testbed, Pablo Serrano, Carlos J. Bernardos, Antonio De La Oliva, Albert Banchs, Ignacio Soto, Michael Zink
Floornet: Deployment And Evaluation Of Amultihop Wireless 802.11 Testbed, Pablo Serrano, Carlos J. Bernardos, Antonio De La Oliva, Albert Banchs, Ignacio Soto, Michael Zink
Michael Zink
A lot of attention has been given to multihop wireless networks lately, but further research—in particular, through experimentation—is needed. This attention has motivated an increase in the number of 802.11-based deployments, both indoor and outdoor. These testbeds, which require a significant amount of resources during both deployment and maintenance, are used to run measurements in order to analyze and understand the limitation and differences between analytical or simulation-based figures and the results from real-life experimentation. This paper makes two major contributions: (i) first, we describe a novel wireless multihop testbed, which we name FloorNet, that is deployed and operated under …
Vehicular Ad Hoc Networks, Hossein Pishro-Nik, Shahrokh Valaee, Maziar Nekovee
Vehicular Ad Hoc Networks, Hossein Pishro-Nik, Shahrokh Valaee, Maziar Nekovee
Hossein Pishro-Nik
No abstract provided.
Density-Matrix-Based Algorithms For Solving Eingenvalue Problems, Eric Polizzi
Density-Matrix-Based Algorithms For Solving Eingenvalue Problems, Eric Polizzi
Eric Polizzi
A fast and stable numerical algorithm for solving the symmetric eigenvalue problem is presented. The technique deviates fundamentally from the traditional Krylov subspace iteration based techniques (Arnoldi and Lanczos algorithms) or other Davidson-Jacobi techniques and takes its inspiration from the contour integration and density-matrix representation in quantum mechanics. It will be shown that this algorithm—named FEAST—exhibits high efficiency, robustness, accuracy, and scalability on parallel architectures. Examples from electronic structure calculations of carbon nanotubes are presented, and numerical performances and capabilities are discussed.
Virtual Circular Array Using Material-Embedded Linear Source Distributions, Dohoon Kwon
Virtual Circular Array Using Material-Embedded Linear Source Distributions, Dohoon Kwon
Do-Hoon Kwon
Linear arrays of sources embedded inside a thin material slab are designed such that they radiate the same fields as a circular array of radiators in free space in a two-dimensional configuration. The design is based on the coordinate transformation approach, where a circular domain containing a distribution of line sources is transformed into a rectangular slab. The source distribution in the transformed space forms two closely-spaced linear arrays and the resulting material slab is matched along the boundary with free space. Full-wave simulations are performed for verification.
Design And Demonstration Of A Small-Animal Up-Conversion Imager, Christopher Salthouse, Scott Hildebrand, Ralph Weissleder, Umar Mahmood
Design And Demonstration Of A Small-Animal Up-Conversion Imager, Christopher Salthouse, Scott Hildebrand, Ralph Weissleder, Umar Mahmood
Christopher Salthouse
This first small-animal up-conversion imager (SAUCI) was developed and used for in-vivo imaging of up-converting nanoparticles (UCNs.) Unlike traditional fluorophores, UCNs absorb multiple lower-energy photons and emit a single higher-energy photon. This unique physical process makes it possible to image deeper into tissue with lower background signals. In vivo imaging of particle accumulation in the liver was demonstrated following intravenous injection of particles.
Superhydrophobicity And Contact-Line Issues, Lc Gao, Ay Fadeev, Tj Mccarthy
Superhydrophobicity And Contact-Line Issues, Lc Gao, Ay Fadeev, Tj Mccarthy
Lixin Gao
The wettability of several superhydrophobic surfaces that were prepared recently by simple, mostly single-step methods is described and compared with the wettability of surfaces that are less hydrophobic. We explain why two length scales of topography can be important for controlling the hydrophobicity of some surfaces (the lotus effect). Contact-angle hysteresis (difference between the advancing, θA, and receding, θR, contact angles) is discussed and explained, particularly with regard to its contribution to water repellency. Perfect hydrophobicity (θA/θR = 180°/180°) and a method for distinguishing perfectly hydrophobic surfaces from those that are almost perfectly hydrophobic are described and discussed. The Wenzel …
Power-Efficient Topology Control For Static Wireless Networks With Switched Beam Directional Antennas, V Namboodiri, Lx Gao, R Janaswamy
Power-Efficient Topology Control For Static Wireless Networks With Switched Beam Directional Antennas, V Namboodiri, Lx Gao, R Janaswamy
Lixin Gao
Topology control problems are associated with assignment of power levels to nodes of a wireless network so that the resulting graph topology satisfies certain properties. In this paper we consider the problem of power-efficient topology control with switched beam directional antennas taking into account their non-uniform radiation pattern within the beamwidth. Previous work in the area have all assumed a uniform gain model with these antennas which renders antenna orientation insignificant as a parameter in topology control algorithms. We present algorithms that take into account a model of non-uniform gain with the objectives of minimizing the total power and maximum …
High Resolution Observations Of Insects In The Atmospheric Boundary Layer, Stephen Frasier, R. F. Contreras
High Resolution Observations Of Insects In The Atmospheric Boundary Layer, Stephen Frasier, R. F. Contreras
Stephen Frasier
High spatial and temporal resolution S-band radar observations of insects in the atmospheric boundary layer (ABL) are described. The observations were acquired with a frequency-modulated continuous-wave (FMCW) radar during the 2002 International H20 Project (IHOP_2002) held in Oklahoma in the months of May and June 2002. During the observational period the boundary layer was convective with a few periods of rain. Rayleigh scattering from particulate scatterers (i.e., insects) dominates the return; however, Bragg scattering from refractive index turbulence is also significant, especially at the top of the afternoon boundary layer. There is a strong diurnal signal in the insect backscatter: …
Terahertz Detection In Single Wall Carbon Nanotubes, Eric Polizzi, K. S. Yngvesson, J. Nicholson, S. H. Adams, C. Chan, K. Fu, R Zannoni
Terahertz Detection In Single Wall Carbon Nanotubes, Eric Polizzi, K. S. Yngvesson, J. Nicholson, S. H. Adams, C. Chan, K. Fu, R Zannoni
Eric Polizzi
It is reported that terahertz radiation from 0.69 to 2.54 THz has been sensitively detected in a device consisting of bundles of carbon nanotubes containing single wall metallic carbon nanotubes, quasioptically coupled through a lithographically fabricated antenna, and a silicon lens. The measured data are consistent with a bolometric detection process in the metallic tubes and the devices show promise for operation well above 4.2 K.
On Inferring And Characterizing Internet Routing Policies, F Wang, L Gao
On Inferring And Characterizing Internet Routing Policies, F Wang, L Gao
Lixin Gao
No abstract provided.
Prediction-Based Routing For Vehicular Ad Hoc Networks, V Namboodiri, L Gao
Prediction-Based Routing For Vehicular Ad Hoc Networks, V Namboodiri, L Gao
Lixin Gao
No abstract provided.
Towards Defect-Tolerant Nanoscale Architectures, C. Andras Moritz, Teng Wang
Towards Defect-Tolerant Nanoscale Architectures, C. Andras Moritz, Teng Wang
C. Andras Moritz
Nanoscale computing systems show great potential but at the same time introduce new challenges not encountered in the world of conventional CMOS designs and manufacturing. For example, these systems need to work around layout and doping constraints resulting from unconventional bottom-up selfassembly, and need to cope with high manufacturing defect rates and transient faults. Unfortunately, most conventional defecttolerance techniques are not directly applicable in nanoscale systems because they have been designed for very small defect rates. In this paper, we explore built-in defect-tolerance techniques on 2-D semiconductor nanowire (NW) arrays to make designs self-healing. Our approach combines circuit and systemlevel …