Publications

Refine Results

(Filters Applied) Clear All

Comparisons between the extended Kalman filter and the state-dependent Riccati estimator

September 1, 2014
  |
Journal Article
Author:
Andrew M. Berman
…
Published in:
J. Guid. Control Dyn., Vol. 37, No. 5, September-October 2014, pp. 1556-67.
Topic:
electronic warfare
R&D area:
R&D group:

Summary

The state-dependent Riccati equation-based estimator is becoming a popular estimation tool for nonlinear systems since it does not use system linearization. In this paper, the state-dependent Riccati equation-based estimator is compared with the widely used extended Kalman filter for three simple examples that appear in the open literature. It is demonstrated that, by simulation, the state-dependent Riccati equation-based estimator at best has comparable results to the extended Kalman filter but is often worse than the extended Kalman filter. In some cases, the state-dependent Riccati equation-based estimator does not converge, even though the system considered satisfies all the mathematical constraints on controllability and observability. Sufficient detail is presented in the paper so that the interested reader cannot only duplicate the results but perhaps make suggestions on how to get the state-dependent Riccati equation-based estimator to perform better.
READ LESS

Summary

The state-dependent Riccati equation-based estimator is becoming a popular estimation tool for nonlinear systems since it does not use system linearization. In this paper, the state-dependent Riccati equation-based estimator is compared with the widely used extended Kalman filter for three simple examples that appear in the open literature. It is...

READ MORE
Comparisons between the extended Kalman filter and the state-dependent Riccati estimator

Content+context=classification: examining the roles of social interactions and linguist content in Twitter user classification

August 24, 2014
  |
Conference Paper
Author:
William M. Campbell
…
Published in:
Proc. Second Workshop on Natural Language Processing for Social Media, SocialNLP, 24 August 2014, pp. 59-65.
Topic:
human language technology
R&D area:
R&D group:

Summary

Twitter users demonstrate many characteristics via their online presence. Connections, community memberships, and communication patterns reveal both idiosyncratic and general properties of users. In addition, the content of tweets can be critical for distinguishing the role and importance of a user. In this work, we explore Twitter user classification using context and content cues. We construct a rich graph structure induced by hashtags and social communications in Twitter. We derive features from this graph structure - centrality, communities, and local flow of information. In addition, we perform detailed content analysis on tweets looking at offensiveness and topics. We then examine user classification and the role of feature types (context, content) and learning methods (propositional, relational) through a series of experiments on annotated data. Our work contrasts with prior approaches in that we use relational learning and alternative, non-specialized feature sets. Our goal is to understand how both content and context are predictive of user characteristics. Experiments demonstrate that the best performance for user classification uses relational learning with varying content and context features.
READ LESS

Summary

Twitter users demonstrate many characteristics via their online presence. Connections, community memberships, and communication patterns reveal both idiosyncratic and general properties of users. In addition, the content of tweets can be critical for distinguishing the role and importance of a user. In this work, we explore Twitter user classification using...

READ MORE
Content+context=classification: examining the roles of social interactions and linguist content in Twitter user classification

VizLinc: integrating information extraction, search, graph analysis, and geo-location for the visual exploration of large data sets

August 24, 2014
  |
Conference Paper
Author:
Joel Acevedo-Aviles
…
Published in:
Proc. KDD 2014 Workshop on Interactive Data Exploration and Analytics, IDEA, 24 August 2014, pp. 10-18.
Topic:
human language technology
R&D area:
R&D group:

Summary

In this demo paper we introduce VizLinc; an open-source software suite that integrates automatic information extraction, search, graph analysis, and geo-location for interactive visualization and exploration of large data sets. VizLinc helps users in: 1) understanding the type of information the data set under study might contain, 2) finding patterns and connections between entities, and 3) narrowing down the corpus to a small fraction of relevant documents that users can quickly read. We apply the tools offered by VizLinc to a subset of the New York Times Annotated Corpus and present use cases that demonstrate VizLinc's search and visualization features.
READ LESS

Summary

In this demo paper we introduce VizLinc; an open-source software suite that integrates automatic information extraction, search, graph analysis, and geo-location for interactive visualization and exploration of large data sets. VizLinc helps users in: 1) understanding the type of information the data set under study might contain, 2) finding patterns...

READ MORE
VizLinc: integrating information extraction, search, graph analysis, and geo-location for the visual exploration of large data sets

Effective Entropy: security-centric metric for memory randomization techniques

August 20, 2014
  |
Conference Paper
Author:
William N. Herlands
…
Published in:
Proc. 7th USENIX Conf. on Cyber Security Experimentation and Test, CSET, 20 August 2014.
Topic:
cyber security
R&D area:
R&D group:

Summary

User space memory randomization techniques are an emerging field of cyber defensive technology which attempts to protect computing systems by randomizing the layout of memory. Quantitative metrics are needed to evaluate their effectiveness at securing systems against modern adversaries and to compare between randomization technologies. We introduce Effective Entropy, a measure of entropy in user space memory which quantitatively considers an adversary's ability to leverage low entropy regions of memory via absolute and dynamic intersection connections. Effective Entropy is indicative of adversary workload and enables comparison between different randomization techniques. Using Effective Entropy, we present a comparison of static Address Space Layout Randomization (ASLR), Position Independent Executable (PIE) ASLR, and a theoretical fine grain randomization technique.
READ LESS

Summary

User space memory randomization techniques are an emerging field of cyber defensive technology which attempts to protect computing systems by randomizing the layout of memory. Quantitative metrics are needed to evaluate their effectiveness at securing systems against modern adversaries and to compare between randomization technologies. We introduce Effective Entropy, a...

READ MORE
Effective Entropy: security-centric metric for memory randomization techniques

Chemical aerosol detection and identification using Raman scattering

August 1, 2014
  |
Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
J. Raman Spectrosc., Vol. 45, No. 8, August 2014, pp. 677-9.
Topic:
detection systems
R&D area:
R&D group:

Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm continuous wave laser Raman scattering. We have demonstrated the Raman scattering detection and identification of an aerosol of isovanillin of mass concentration of 1.8 ng/cm^3 with a signal-to-noise ratio of about 19 in 30 s for the 116-cm^-1 mode with a Raman cross section of 3.3 x 10^-28 cm^2 using 8-W double-pass laser power.
READ LESS

Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm...

READ MORE
Chemical aerosol detection and identification using Raman scattering

Silicon photonics devices for integrated analog signal processing and sampling

August 1, 2014
  |
Journal Article
Author:
Steven Jay Spector
…
Published in:
Nanophotonics, Vol. 3, No. 4-5, 1 August 2014, pp. 313-27.
Topic:
photonics
R&D area:
R&D group:

Summary

Silicon photonics offers the possibility of a reduction in size weight and power for many optical systems, and could open up the ability to build optical systems with complexities that would otherwise be impossible to achieve. Silicon photonics is an emerging technology that has already been inserted into commercial communication products. This technology has also been applied to analog signal processing applications. MIT Lincoln Laboratory in collaboration with groups at MIT has developed a toolkit of silicon photonic devices with a focus on the needs of analog systems. This toolkit includes low-loss waveguides, a high-speed modulator, ring resonator based filter bank, and all-silicon photodiodes. The components are integrated together for a hybrid photonic and electronic analog-to-digital converter. The development and performance of these devices will be discussed. Additionally, the linear performance of these devices, which is important for analog systems, is also investigated.
READ LESS

Summary

Silicon photonics offers the possibility of a reduction in size weight and power for many optical systems, and could open up the ability to build optical systems with complexities that would otherwise be impossible to achieve. Silicon photonics is an emerging technology that has already been inserted into commercial communication...

READ MORE
Silicon photonics devices for integrated analog signal processing and sampling

Development of CCDs for REXIS on OSIRIS-REx

July 24, 2014
  |
Conference Paper
Author:
Kevin K. Ryu
…
Published in:
SPIE, Vol. 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 22 June 2014, 91444O.
Topic:
optics
R&D area:
R&D group:

Summary

The Regolith x-ray Imaging Spectrometer (REXIS) is a coded-aperture soft x-ray imaging instrument on the OSIRIS-REx spacecraft to be launched in 2016. The spacecraft will fly to and orbit the near-Earth asteroid Bennu, while REXIS maps the elemental distribution on the asteroid using x-ray fluorescence. The detector consists of a 2x2 array of back-illuminated 1kX1k frame transfer CCDs with a flight heritage to Suzaku and Chandra. The back surface has a thing p+-doped layer deposited by molecular-beam epitaxy (MBE) for maximum quantum efficiency and energy resolution at low x-ray energies. The CCDs also feature an integrated optical-blocking filter (OBF) to suppress visible and near-infrared light. The OBF is an aluminum film deposited directly on the CCD back surface and is mechanically more robust and less absorptive of x-rays than the conventional free-standing aluminum-coated polymer films. The CCDs have charge transfer inefficiencies of less than 10^-6, and dark current of le-/pixel/second at the REXIS operating temperature of -60 degrees C. The resulting spectral resolution is 115 eV at 2 KeV. The extinction ratio of the filter is ~10^12 at 625 nm.
READ LESS

Summary

The Regolith x-ray Imaging Spectrometer (REXIS) is a coded-aperture soft x-ray imaging instrument on the OSIRIS-REx spacecraft to be launched in 2016. The spacecraft will fly to and orbit the near-Earth asteroid Bennu, while REXIS maps the elemental distribution on the asteroid using x-ray fluorescence. The detector consists of a...

READ MORE
Development of CCDs for REXIS on OSIRIS-REx

Using 3D printing to visualize social media big data

July 23, 2014
  |
Journal Article
Author:
Zachary J. Weber
…
Published in:
HPEC 2014: IEEE Conf. on High Performance Extreme Computing, 9-11 September 2014.
Topic:
3D printing
R&D area:
R&D group:

Summary

Big data volume continues to grow at unprecedented rates. One of the key features that makes big data valuable is the promise to find unknown patterns or correlations that may be able to improve the quality of processes or systems. Unfortunately, with the exponential growth in data, users often have difficulty in visualizing the often-unstructured, non-homogeneous data coming from a variety of sources. The recent growth in popularity of 3D printing has ushered in a revolutionary way to interact with big data. Using a 3D printed mockup up a physical or notional environment, one can display data on the mockup to show real-time data patterns. In this poster and demonstration, we describe the process of 3D printing and demonstrate an application of displaying Twitter data on a 3D mockup of the Massachusetts Institute of Technology (MIT) campus, known as LuminoCity.
READ LESS

Summary

Big data volume continues to grow at unprecedented rates. One of the key features that makes big data valuable is the promise to find unknown patterns or correlations that may be able to improve the quality of processes or systems. Unfortunately, with the exponential growth in data, users often have...

READ MORE
Using 3D printing to visualize social media big data

Simultaneous transmit and receive antenna isolation improvement in scattering environments

July 6, 2014
  |
Conference Paper
Author:
Kenneth E. Kolodziej
…
Published in:
APS/URSI 2014, IEEE Int. Symp. on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 6-11 July 2014.
Topic:
antennas
R&D area:
R&D group:

Summary

Simultaneous transmit and receive (STAR) systems require high isolation between the transmitter and receiver to avoid self-interference. Antenna isolation degradation stems from errors in the physical construction and beamformer design, as well as reflections from scattering objects in the environment. An RF canceller subsystem can be inserted at the antenna feeds to improve the isolation in the presence of reflecting objects by 30 dB over 30 MHz centered at 2.45 GHz. This results in 90 dB of effective antenna isolation when paired with a high-isolation antenna that exhibits omni-directional radiation patterns, signifying that STAR systems can be practically deployed.
READ LESS

Summary

Simultaneous transmit and receive (STAR) systems require high isolation between the transmitter and receiver to avoid self-interference. Antenna isolation degradation stems from errors in the physical construction and beamformer design, as well as reflections from scattering objects in the environment. An RF canceller subsystem can be inserted at the antenna...

READ MORE
Simultaneous transmit and receive antenna isolation improvement in scattering environments

Wideband antenna array for simultaneous transmit and receive (STAR) applications

July 6, 2014
  |
Conference Paper
Author:
William F. Moulder
…
Published in:
2014 IEEE Int. Symp. on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 6-11 July 2014.
Topic:
antennas
R&D area:
R&D group:

Summary

A wideband antenna array for Simultaneous Transmit and Receive (STAR) applications is presented. The design is comprised of a ring array of TEM horns, and a monocone at the array's center. When the array is phased with the first order circular mode, it is isolated from the monocone. Thus, the array may be used in reception while the monocone is used in transmission, or vice versa. The array and monocone both produce quasi-omnidirectional patterns in the azimuthal planes. Simulations suggest that the design operates across an 8.4 : 1 bandwidth. This wide bandwidth is possible through the use of a novel capacitive feed employed in the TEM horn array.
READ LESS

Summary

A wideband antenna array for Simultaneous Transmit and Receive (STAR) applications is presented. The design is comprised of a ring array of TEM horns, and a monocone at the array's center. When the array is phased with the first order circular mode, it is isolated from the monocone. Thus, the...

READ MORE
Wideband antenna array for simultaneous transmit and receive (STAR) applications
641-650 of 2301