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Articles 1 - 30 of 41
Full-Text Articles in Engineering
Concept Tests For A New Wire Flying Vehicle Designed To Achieve High Horizontal Resolution Profiling In Deep Water, Chris Roman, Dave Hebert
Concept Tests For A New Wire Flying Vehicle Designed To Achieve High Horizontal Resolution Profiling In Deep Water, Chris Roman, Dave Hebert
Christopher N. Roman
Efficiently profiling the water column to achieve both high vertical and horizontal resolution from a moving vessel in deep water is difficult. Current solutions, such as CTD tow-yos, moving vessel profilers, and undulating tow bodies, are limited by ship speed or water depth. As a consequence, it is difficult to obtain oceanographic sections with sufficient resolution to identify many relevant scales over the deeper sections of the water column. This paper presents a new concept for a profiling vehicle that slides up and down a towed wire in a controlled manner using the lift created by wing foils. The wings …
Asymptotic Data Rates Of Receive-Diversity Systems With Mmse Estimation And Interferers At Correlated Locations, Siddhartan Govindasamy
Asymptotic Data Rates Of Receive-Diversity Systems With Mmse Estimation And Interferers At Correlated Locations, Siddhartan Govindasamy
Siddhartan Govindasamy
An asymptotic technique is presented to characterize the bits/symbol achievable on a representative wireless link in a spatially distributed network with active interferers at correlated positions, N receive diversity branches, and linear Minimum-Mean-Square-Error (MMSE) receivers. The models analyzed include analogs to Matern type I and type II networks. It is found that for our network models, with large N, the correlation between interferer positions does not significantly influence the bits/symbol resulting in simple approximations for the data rates achievable in such networks with moderately large numbers of diversity branches.
Direct Sequence Modified Time Hopping Ppm Over Ultra Wideband S-V Channel, Peter Vial, Beata Wysocki, Tadeusz Wysocki
Direct Sequence Modified Time Hopping Ppm Over Ultra Wideband S-V Channel, Peter Vial, Beata Wysocki, Tadeusz Wysocki
Dr Peter Vial
A three position Pulse Position Modulation (PPM) scheme is proposed for a Direct Sequence Time Hopping Ultra Wideband wireless communication system. The channel is based on the Saleh-Valenzuela model. We show that by adapting the Space Time Spreading technique to use three pulse positions in a single input single output system representing -2,0,2 an improvement in Bit Error Rate is achieved compared to sending the same bits using two pulse positions only. In addition, the bit access rate is doubled as two bits can be successfully sent in the same time using our proposed system.
Non-Optimal Receiver For Space Time Spreading Across A Time Hopping Over Ultra Wideband Ppm, Peter Vial, Beata Wysocki, Tadeusz Wysocki
Non-Optimal Receiver For Space Time Spreading Across A Time Hopping Over Ultra Wideband Ppm, Peter Vial, Beata Wysocki, Tadeusz Wysocki
Dr Peter Vial
A novel non-optimal chip based technique is proposed to use two antennas to transmit data across a Direct Sequence Time Hopping Ultra Wideband dual antenna wireless communication system to a single receiver. The spread data is sent over the independent channels using the Space Time Spreading technique to encode the chips which are sent on each antenna simultaneously. A hard decision is made at each chip of the spreading code received based on the known Channel State Information which Pulse Position Modulated signal was received from each antenna. The paper shows that by adapting the Space Time Spreading technique to …
Orthogonal Spreading Sequences Constructed Using Hall’S Difference Set, Jennifer Seberry, Le Chung Tran, Yejing Wang, Beata Wysocki, Tadeusz Wysocki, Ying Zhao
Orthogonal Spreading Sequences Constructed Using Hall’S Difference Set, Jennifer Seberry, Le Chung Tran, Yejing Wang, Beata Wysocki, Tadeusz Wysocki, Ying Zhao
Dr Le Chung Tran
In the paper we propose a new set of orthogonal spreading sequences based on the Hadamard matrix of order 32 constructed using the Hall difference set. The proposed sequences are characterised by low peaks in the aperiodic cross-correlation functions and have also good aperiodic auto-correlation properties.
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes In Radio Channels, Le Chung Tran, Tadeusz Wysocki, Jennifer Seberry, Alfred Mertins
A Generalized Algorithm For The Generation Of Correlated Rayleigh Fading Envelopes In Radio Channels, Le Chung Tran, Tadeusz Wysocki, Jennifer Seberry, Alfred Mertins
Dr Le Chung Tran
Although generation of correlated Rayleigh fading envelopes has been intensively considered in the literature, all conventional methods have their own shortcomings, which seriously impede their applicability. In this paper, a very general, straightforward algorithm for generation of an arbitrary number of Rayleigh envelopes with any desired, equal or unequal power, in wireless channels either with or without Doppler frequency shifts, is proposed. The proposed algorithm can be applied in case of spatial correlation, such as with antenna arrays in Multiple Input Multiple Output (MIMO) systems, or spectral correlation between the random processes like in Orthogonal Frequency Division Multiplexing (OFDM) systems. …
Casting A Wider Net, Lynn Stein
Casting A Wider Net, Lynn Stein
Lynn Andrea Stein
This article is a book review of Mung Chiang's book Networked Life: 20 Questions and Answers. In this text intended for both classroom and online learning, Chiang uses questions about our online lives to explore the technology and computer science behind the Internet, wireless, and Web industries.
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos Hadjicostis, Rahul Mangharam, George Pappas
The Wireless Control Network: Monitoring For Malicious Behavior, Shreyas Sundaram, Miroslav Pajic, Christoforos Hadjicostis, Rahul Mangharam, George Pappas
Rahul Mangharam
We consider the problem of stabilizing a plant with a network of resource constrained wireless nodes. In a companion paper, we developed a protocol where each node repeatedly transmits a linear combination of the values in its neighborhood. For certain topologies, we showed that these linear combinations can be designed so that the closed loop system is stable (i.e., the wireless network itself acts as a controller for the plant). In this paper, we design a Intrusion Detection System (IDS) for this control scheme, which observes the transmissions of certain nodes in the network and uses that information to (a) …
A Dipolar Coupling Based Strategy For Simultaneous Resonance Assignment And Structure Determination Of Protein Backbones, Fang Tian, Homayoun Valafar, James Prestegard
A Dipolar Coupling Based Strategy For Simultaneous Resonance Assignment And Structure Determination Of Protein Backbones, Fang Tian, Homayoun Valafar, James Prestegard
Homayoun Valafar
A new approach for simultaneous protein backbone resonance assignment and structure determination by NMR is introduced. This approach relies on recent advances in high-resolution NMR spectroscopy that allow observation of anisotropic interactions, such as dipolar couplings, from proteins partially aligned in field ordered media. Residual dipolar couplings are used for both geometric information and a filter in the assembly of residues in a sequential manner. Experimental data were collected in less than one week on a small redox protein, rubredoxin, that was 15N enriched but not enriched above 1% natural abundance in 13C. Given the acceleration possible with partial 13C …
Stir-Ing The Wireless Medium With Self-Tuned, Inference-Based, Real-Time Jamming, Bruce Debruhl, Yu Seung Kim, Zachary Weinberg, Patrick Tague
Stir-Ing The Wireless Medium With Self-Tuned, Inference-Based, Real-Time Jamming, Bruce Debruhl, Yu Seung Kim, Zachary Weinberg, Patrick Tague
Patrick Tague
Jamming, broadcasting to intentionally interfere with wireless reception, has long been a problem for wireless systems. Recent research demonstrates numerous advances in jamming techniques that increase attack efficiency or reduce the probability an attack will be detected by choosing attack parameters based on a system’s configuration. In this work, we extend the attacker’s capabilities by modifying the attack parameters in response to the observed performance of the target system, effectively creating a feedback loop in our attack model. This framework allows for more intricate attack models that are tuned online allowing for closer to optimal attacks against legitimate systems. To …
Floating-Gate Devices: They Are Not Just For Digital Memories Anymore, Paul Hasler, Bradley Minch, Chris Diorio
Floating-Gate Devices: They Are Not Just For Digital Memories Anymore, Paul Hasler, Bradley Minch, Chris Diorio
Bradley Minch
Since the first reported floating-gate structure in 1967, floating-gate transistors have been used widely to store digital information for long periods in structures such as EPROMs and EEPROMs. Recently floating-gate devices have found applications as analog memories, analog and digital circuit elements, and adaptive processing elements. Floating-gate devices have found commerical applications, e.g. ISD, for long-term non-volatile information storage devices for analog applications. The focus of floating-gate devices has been towards fabrication in standard CMOS processes, as opposed to the specialized processes for fabricating digital non-volatile memories. Floating-gate circuits can be designed at any or all of three levels: analog …
A Floating-Gate Technology For Digital Cmos Processes, Bradley Minch, Paul Hasler
A Floating-Gate Technology For Digital Cmos Processes, Bradley Minch, Paul Hasler
Bradley Minch
We discuss the possibility of developing high-quality floating-gate memories and circuits in digital CMOS technologies that have only one layer of polysilicon. Here, the primary concern is whether or not we can get adequate control-gate linearity from MOS capacitors. We employ two experimental procedures to address this issue and find acceptable floating-gate circuit behaviour with MOS capacitors. First, we simultaneously characterize an MOS capacitor and a linear capacitor; the experimental data show that MOS capacitors behave similarly to linear capacitors over a finite, but usable range. Second, we characterize two typical floating-gateMOS circuit primitives, a floating-gate amplifier and a multiple-input …
Roach: An Autonomous 2.4g Crawling Hexapod Robot, Aaron Hoover, Erik Steltz, Ronald Fearing
Roach: An Autonomous 2.4g Crawling Hexapod Robot, Aaron Hoover, Erik Steltz, Ronald Fearing
Aaron M. Hoover
This work presents the design, fabrication, and testing of a novel hexapedal walking millirobot using only two actuators. Fabricated from S2-glass reinforced composites and flexible polymer hinges using the smart composite microstructures (SCM) process, the robot is capable of speeds up to 1 body length/sec or approximately 3 cm/s. All power and control electronics are onboard and remote commands are enabled by an IrDA link. Actuation is provided by shape memory alloy wire. At 2.4 g including control electronics and battery, RoACH is the smallest and lightest autonomous legged robot produced to date.
Medic: A Legged Millirobot Utilizing Novel Obstacle Traversal, Nicholas Kohut, Aaron Hoover, Kevin Ma, Stanley Baek, Ronald Fearing
Medic: A Legged Millirobot Utilizing Novel Obstacle Traversal, Nicholas Kohut, Aaron Hoover, Kevin Ma, Stanley Baek, Ronald Fearing
Aaron M. Hoover
This work presents the design, fabrication, capabilities, and obstacle traversal mechanics of MEDIC (MillirobotEnabled Diagnostic of Integrated Circuits), a small legged robot able to overcome a varied array of obstacles. MEDIC features a hull that keeps its body in contact with the ground at all times, and uses only four actuators to move forward, turn, mount obstacles, and move in reverse. The chassis is fabricated using a Smart Composite Microstructures (SCM) approach and the robot is actuated by coiled Shape Memory Alloy (SMA). MEDIC also features a camera which will be useful for navigation in the future.
Systematic Study Of The Performance Of Small Robots On Controlled Laboratory Substrates, Chen Li, Aaron Hoover, Paul Birkmeyer, Paul Umbanhowar, Ronald Fearing, Daniel Goldman
Systematic Study Of The Performance Of Small Robots On Controlled Laboratory Substrates, Chen Li, Aaron Hoover, Paul Birkmeyer, Paul Umbanhowar, Ronald Fearing, Daniel Goldman
Aaron M. Hoover
The design of robots able to locomote effectively over a diversity of terrain requires detailed ground interaction models; unfortunately such models are lacking due to the complicated response of real world substrates which can yield and flow in response to loading. To advance our understanding of the relevant modeling and design issues, we conduct a comparative study of the performance of DASH and RoACH, two small, biologically inspired, six legged, lightweight (~10 cm, ~20 g) robots fabricated using the smart composite microstructure (SCM) process. We systematically examine performance of both robots on rigid and flowing substrates. Varying both ground properties …
Fast Scale Prototyping For Folded Millirobots, Aaron Hoover, Ronald Fearing
Fast Scale Prototyping For Folded Millirobots, Aaron Hoover, Ronald Fearing
Aaron M. Hoover
We present a set of tools and a process, making use of inexpensive and environmentally friendly materials, that enable the rapid realization of fully functional large scale prototypes of folded mobile millirobots. By mimicking the smart composite microstructure (SCM) process at a 2–10X scale using posterboard, and commonly available polymer films, we can realize a prototype design in a matter of minutes compared with days for a complicated SCM design at the small scale. The time savings enable a significantly shorter design cycle by allowing forimmediate discovery of design flaws and introduction of design improvements prior to beginning construction at …
A Rapidly Prototyped 2-Axis Positioning Stage For Microassembly Using Large Displacement Compliant Mechanisms, Aaron Hoover, Srinath Avadhanula, Richard Groff, Ronald Fearing
A Rapidly Prototyped 2-Axis Positioning Stage For Microassembly Using Large Displacement Compliant Mechanisms, Aaron Hoover, Srinath Avadhanula, Richard Groff, Ronald Fearing
Aaron M. Hoover
Compliant mechanisms provide an attractive alternative to conventional rigid mechanisms in the design of ultra low-cost precision positioning systems. The desirable performance characteristics of these mechanisms including freedom from backlash, long life, light weight, and ease of fabrication/assembly make them an ideal solution to the problem of inexpensive precision positioning for microassembly. This paper presents a design for a 2 axis precision positioning system which makes use of large displacement compliant mechanisms, a room temperature and pressure molding fabrication process, commodity hardware, and a piecewise linear interpolation compensation scheme to achieve positioning performance suitable for automated assembly of sub-centimeter robotic …
Analysis Of Off-Axis Performance Of Compliant Mechanisms With Applications To Mobile Millirobot Design, Aaron Hoover, Ronald Fearing
Analysis Of Off-Axis Performance Of Compliant Mechanisms With Applications To Mobile Millirobot Design, Aaron Hoover, Ronald Fearing
Aaron M. Hoover
We present an approach to quantifying the off-axis stiffness properties of parallel compliant mechanisms used in the design of mobile millirobots. By transforming the stiffness of individual flexure elements and rigid links comprising a compliant mechanism into a global coordinate system, we enable the formulation of an equivalent mechanism stiffness. Using that stiffness in concert with an energy-based performance metric, we predict theperformance of a compliant mechanism subjected to a prescribed set of forces in the global coordinate system. We analyze a flexure-based Sarrus linkage and use the performance metric to improve the design by adding topological redundancy. Finally, our …
Rapidly Prototyped Orthotweezers For Automated Microassembly, Aaron Hoover, Ronald Fearing
Rapidly Prototyped Orthotweezers For Automated Microassembly, Aaron Hoover, Ronald Fearing
Aaron M. Hoover
We describe the design, fabrication, and testing of an ultra-low cost orthotweezers system for microassembly. By utilizing rapid prototyping technology, compliant mechanisms, and commodity-grade actuators and sensors, we significantly reduce the complexity and cost of the previous Orthotweezers system without sacrificing functionality. With a force resolution of 0.7mN and a worst case mean positioning repeatability of 23 mum, the system is capable of dexterously manipulating rectangular parts with dimensions 200 mum times 200 mum times 100 mum. Such blocks can then be temporarily attached to thin, delicate, or oddly shaped parts to enable handling and ultimately assembly of micromechanical structures. …
Bio-Inspired Design And Dynamic Maneuverability Of A Minimally Actuated Six-Legged Robot, Aaron Hoover, Samuel Burden, Xiao-Yu Fu, S. Sastry, Ronald Fearing
Bio-Inspired Design And Dynamic Maneuverability Of A Minimally Actuated Six-Legged Robot, Aaron Hoover, Samuel Burden, Xiao-Yu Fu, S. Sastry, Ronald Fearing
Aaron M. Hoover
Rapidly running arthropods like cockroaches make use of passive dynamics to achieve remarkable locomotion performance with regard to stability, speed, and maneuverability. In this work, we take inspiration from these organisms to design, fabricate, and control a 10cm, 24 gram underactuated hexapedal robot capable of running at 14 body lengths per second and performing dynamic turning maneuvers. Our design relies on parallel kinematic mechanisms fabricated using the scaled smart composite microstructures (SCM) process and viscoelastic polymer legs with tunable stiffness. In addition to the novel robot design, we present experimental validation of the lateral leg spring (LLS) locomotion model's prediction …
Perimeter Patrol On Autonomous Surface Vehicles Using Marine Radar, Elena Oleynikova, Nicole Lee, Andrew Barry, Joseph Holler, David Barrett
Perimeter Patrol On Autonomous Surface Vehicles Using Marine Radar, Elena Oleynikova, Nicole Lee, Andrew Barry, Joseph Holler, David Barrett
David Barrett
Perimeter patrol enhances the utility of autonomous surface vehicles (ASVs) by enabling many security and scientific missions, including harbor protection, water sampling, and geological survey. We present a novel approach to perimeter patrol that uses only two sensors: commercial off-the-shelf available marine radar and the heading information from a GPS. Our algorithm performs computer vision morphological operations on the radarimage to find a suitable path around shore and choose an appropriate next waypoint. Our method has proved robust to a variety of field conditions, allowing us to demonstrate the autonomous navigation of a 3.5 km perimeter lake.
The Optimal Control Of A Flexible Hull Robotic Undersea Vehicle Propelled By An Oscillating Foil, David Barrett, Mark Grosenbaugh, Michael Triantafyllou
The Optimal Control Of A Flexible Hull Robotic Undersea Vehicle Propelled By An Oscillating Foil, David Barrett, Mark Grosenbaugh, Michael Triantafyllou
David Barrett
Determining the optimal swimming motion for a flexible hull robotic undersea vehicle propelled by an oscillating foil is an acutely complex problem involving the vehicle's body kinematics and the hydrodynamics of the surrounding water. The overall intractability of the hydrodynamics of a flexible body precludes a purely analytical solution. The immense size of the experimental variable space prevents a purely empirical one. In order to overcome both difficulties, we have developed a self-optimizing motion controller based on a genetic algorithm. This controller effectively uses evolutionary principles to exponentially optimize swimming performance.
A Parameterized Stereo Vision Core For Fpgas, Mark Chang, Stephen Longfield
A Parameterized Stereo Vision Core For Fpgas, Mark Chang, Stephen Longfield
Mark L. Chang
We present a parameterized stereo vision core suitable for a wide range of FPGA targets and stereo vision applications. By enabling easy tuning of algorithm parameters, our system allows for rapid exploration of the design space and simpler implementation of high-performance stereo vision systems. This implementation utilizes the census transform algorithm to calculate depth information from a pair of images delivered from a simulated stereo camera pair. This work advances our previous work through implementation improvements, a stereo camera pair simulation framework, and a scalable stereo vision core.
Precis: A Usercentric Word-Length Optimization Tool, Mark Chang, Scott Hauck
Precis: A Usercentric Word-Length Optimization Tool, Mark Chang, Scott Hauck
Mark L. Chang
Translating an algorithm designed for a general-purpose processor into an algorithm optimized for custom logic requires extensive knowledge of the algorithm and the target hardware. Precis lets designers analyze the precision requirements of algorithms specified in Matlab. The design time tool combines simulation, user input, and program analysis to help designers focus their manual precision optimization efforts.
All Your Jammers Belong To Us - Localization Of Wireless Sensors Under Jamming Attack, Yu Seung Kim, Frank Mokaya, Eric Chen, Patrick Tague
All Your Jammers Belong To Us - Localization Of Wireless Sensors Under Jamming Attack, Yu Seung Kim, Frank Mokaya, Eric Chen, Patrick Tague
Patrick Tague
Accurately determining locations of nodes in mobile wireless network is crucial for a myriad of applications. Unfortunately, most localization techniques are vulnerable to jamming attacks where the adversary attempts to disrupt communication between legitimate nodes in the network. In this paper, we propose an approach to localize a wireless node by using jamming attack as the advantage of the network. Our localization technique is divided into two steps. First, we discover the location of the jammer using power adaptation techniques. Then, we use these properties to extrapolate the locations of jammed nodes. We design a localization protocol using this technique, …
S-Span: Secure Smart Posters In Android Using Nfc (Demo), Jason Wu, Lin Qi, Nishant Kumar, Ram Shankar Siva Kumar, Patrick Tague
S-Span: Secure Smart Posters In Android Using Nfc (Demo), Jason Wu, Lin Qi, Nishant Kumar, Ram Shankar Siva Kumar, Patrick Tague
Patrick Tague
Smart posters are a promising new use case for NFC-enabled mobile devices, but to date there has been a general lack of security mechanisms for NFC smart posters. We present S-SPAN - a secure smart poster system consisting of three parts: an administrative web interface for managing posters, a backend server for storing and serving data, as well as an Android application for end-users. S-SPAN enforces confidentiality and integrity of smart poster data as well as authentication/authorization of administrators and end-users, thus ensuring that only authorized users can access the content.
Living With Boisterous Neighbors: Studying The Interaction Of Adaptive Jamming And Anti-Jamming, Bruce Debruhl, Patrick Tague
Living With Boisterous Neighbors: Studying The Interaction Of Adaptive Jamming And Anti-Jamming, Bruce Debruhl, Patrick Tague
Patrick Tague
Jamming has long been a problem in wireless communications, but with recent advances in adaptive jamming, adaptive anti-jamming, and other advanced physical layer security techniques, it is hard to understand whether we can keep the jammer at bay. In this work, we consider this problem and introduce a game-theoretic framework which gives us a tool to analyze the complex adaptive jamming and anti-jamming space. To illustrate the strengths and weaknesses in intelligent jamming and anti-jamming techniques, we present a straightforward two-player instance and analyze a number of possible jamming and anti-jamming techniques.
Method Of And Apparatus For Computer-Aided Generation Of Variations Of A Sequence Of Symbols, Such As A Musical Piece, And Other Data, Character Or Image Sequences, Diana Dabby
Diana Dabby
A procedure for generating different variations of a sequence of symbols, such as a musical piece, based on the properties of a chaotic system--most notably, sensitive dependence on the initial condition--is described and demonstrated. This method preferably uses a fourth order Runge-Kutta implementation of a chaotic system. Bach's Prelude in C Major from the Well-Tempered Clavier, Book I serves as the illustrative example since it is well-known and easily accessible. Variations of the Bach can be heard that are very close to the original while others diverge further. The system is designed for composers who, having created a through-composed work …
(Re)Defining Computing Curricula By (Re)Defining Computing, Charles Isbell, Lynn Stein, Robb Cutler, Jeffrey Forbes, Linda Fraser, John Impagliazzo, Viera Proulx, Steve Russ, Richard Thomas, Yan Xu
(Re)Defining Computing Curricula By (Re)Defining Computing, Charles Isbell, Lynn Stein, Robb Cutler, Jeffrey Forbes, Linda Fraser, John Impagliazzo, Viera Proulx, Steve Russ, Richard Thomas, Yan Xu
Lynn Andrea Stein
What is the core of Computing? This paper defines the discipline of computing as centered around the notion of modeling, especially those models that are automatable and automatically manipulable. We argue that this central idea crucially connects models with languages and machines rather than focusing on and around computational artifacts, and that it admits a very broad set of fields while still distinguishing the discipline from mathematics, engineering and science. The resulting computational curriculum focuses on modeling, scales and limits, simulation, abstraction, and automation as key components of a computationalist mindset.
An Atemporal Frame Problem, Lynn Stein
An Atemporal Frame Problem, Lynn Stein
Lynn Andrea Stein
Given some changes in the world, the frame problem is the problem of determining that most things in the world haven't changed. Since change is generally taken to mean "change over time", the frame problem is generally assumed to be a problem of temporal reasoning, and most examples of the frame problem are couched in terms of the effects of actions. In this paper, I point out the fallacy underlying this approach, and demonstrate something very much like the frame problem that is completely independent of time: the counterfactual validity problem. I show that this "atemporal frame problem" proves damning …