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Approaches for language identification in mismatched environments

Summary

In this paper, we consider the task of language identification in the context of mismatch conditions. Specifically, we address the issue of using unlabeled data in the domain of interest to improve the performance of a state-of-the-art system. The evaluation is performed on a 9-language set that includes data in both conversational telephone speech and narrowband broadcast speech. Multiple experiments are conducted to assess the performance of the system in this condition and a number of alternatives to ameliorate the drop in performance. The best system evaluated is based on deep neural network (DNN) bottleneck features using i-vectors utilizing a combination of all the approaches proposed in this work. The resulting system improved baseline DNN system performance by 30%.
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Summary

In this paper, we consider the task of language identification in the context of mismatch conditions. Specifically, we address the issue of using unlabeled data in the domain of interest to improve the performance of a state-of-the-art system. The evaluation is performed on a 9-language set that includes data in...

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Automated assessment of secure search systems

Summary

This work presents the results of a three-year project that assessed nine different privacy-preserving data search systems. We detail the design of a software assessment framework that focuses on low system footprint, repeatability, and reusability. A unique achievement of this project was the automation and integration of the entire test process, from the production and execution of tests to the generation of human-readable evaluation reports. We synthesize our experiences into a set of simple mantras that we recommend following in the design of any assessment framework.
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Summary

This work presents the results of a three-year project that assessed nine different privacy-preserving data search systems. We detail the design of a software assessment framework that focuses on low system footprint, repeatability, and reusability. A unique achievement of this project was the automation and integration of the entire test...

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Ultrawideband time-delay steered UHF dipole linear array antenna

Published in:
2013 IEEE Int. Symp. On Phased Array Systems and Technology, 15-18 October 2013.

Summary

An ultrawideband fixed time-delay steered UHF dipole array antenna has been developed for coverage in the 300 to 450 MHz frequency range for communications or radar applications. The antenna utilizes a parasitically-tuned dipole array for linear polarization and is mounted over a ground plane. Numerical electromagnetic simulations were used to analyze and optimize the antenna parameters prior to fabrication. Measurements of the prototype antenna in an anechoic chamber demonstrate the antenna's reflection coefficient and radiation gain pattern performance.
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Summary

An ultrawideband fixed time-delay steered UHF dipole array antenna has been developed for coverage in the 300 to 450 MHz frequency range for communications or radar applications. The antenna utilizes a parasitically-tuned dipole array for linear polarization and is mounted over a ground plane. Numerical electromagnetic simulations were used to...

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Ultrawideband cavity-backed resistively loaded planar dipole array for ground penetrating radar

Published in:
2013 IEEE Int. Symp. On Phased Array Systems and Technology, 15-18 October 2013.

Summary

An ultrawideband (UWB) cavity-backed resistively loaded planar dipole array antenna has been developed for the 100 to 400 MHz frequency range for ground penetrating radar applications. The antenna has been designed with a 3m aperture to perform surveys of a wide swath of ground from a moving vehicle. The performance of the UWB array is quantified by moment method simulations of the electromagnetic field penetration into lossy soil. Integration of the UWB array onto vehicle is discussed.
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Summary

An ultrawideband (UWB) cavity-backed resistively loaded planar dipole array antenna has been developed for the 100 to 400 MHz frequency range for ground penetrating radar applications. The antenna has been designed with a 3m aperture to perform surveys of a wide swath of ground from a moving vehicle. The performance...

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Pixel-processing imager development for directed energy applications

Summary

Tactical high-energy laser (HEL) systems face a range of imaging-related challenges in wavefront sensing, acquiring and tracking targets, selecting the HEL aimpoint, and assessing lethality. Accomplishing these functions in a timely fashion may be limited by competing requirements on total field of regard, target resolution, signal to noise, and focal plane readout bandwidth. In this paper, we explore the applicability of an emerging pixel-processing imager (PPI) technology to these challenges. The on-focal-plane signal processing capabilities of the MIT Lincoln Laboratory PPI technology have recently been extended in support of directed energy applications. We describe this work as well as early results from a new PPI-based short-wave-infrared focal plane readout capable of supporting diverse applications such as low-latency Shack-Hartmann wavefront sensing, centroid computation, and Fitts correlation tracking.
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Summary

Tactical high-energy laser (HEL) systems face a range of imaging-related challenges in wavefront sensing, acquiring and tracking targets, selecting the HEL aimpoint, and assessing lethality. Accomplishing these functions in a timely fashion may be limited by competing requirements on total field of regard, target resolution, signal to noise, and focal...

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Ring array antenna with optimized beamformer for simultaneous transmit and receive

Published in:
2012 IEEE Antennas and Propagation Society International Symp. and USNC/URSI National Radio Sci. Mtg., 8-14 July 2012.

Summary

In order to avoid self-interference, Simultaneous Transmit And Receive (STAR) systems require low mutual coupling between their respective transmit and receive antennas. This paper discusses the development of an 8-element transmit ring array antenna on a circular ground plane with a raised receive element. When combined with a beamformer that supplies linear progressive phase shifts to the array with opposing elements phased 180-degrees apart, the receive and transmit antennas are measured to exhibit 55 dB of isolation and omni-directional patterns in the 2.4 to 2.5 GHz band.
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Summary

In order to avoid self-interference, Simultaneous Transmit And Receive (STAR) systems require low mutual coupling between their respective transmit and receive antennas. This paper discusses the development of an 8-element transmit ring array antenna on a circular ground plane with a raised receive element. When combined with a beamformer that...

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The MIT IAP radar course: build a small radar system capable of sensing range, Doppler, and synthetic aperture (SAR) imaging

Published in:
Proc. of the 2012 IEEE Radar Conf., 7-11 May 2012.

Summary

MIT Lincoln Laboratory sponsored a radar short course at MIT campus during the January 2011 Independent Activities Period (IAP). The objective of this course was to generate student interest in applied electromagnetics, antennas, radio frequency (RF) electronics, analog circuits, and signal processing by building a short-range radar sensor and using it in a series of field tests. Lectures on the fundamentals of radar, modular RF design, antennas, pulse compression and synthetic aperture radar (SAR) imaging were presented. Teams of three students built a radar system from a kit. This kit was developed by the authors and uses a frequency modulated continuous wave (FMCW) architecture. To save costs, empty metal coffee cans are used for antennas, components are mounted on a wood block, the system uses only six coaxial microwave parts, analog circuitry on a solderless breadboard, and runs on eight AA batteries. Analog data is acquired by the audio input port on a laptop computer. The total cost of each kit was $360 which made this radar technology accessible to students. Of the nine student groups, all succeeded in building their radar, acquiring Doppler vs. time and range vs. time plots, seven succeeded in acquiring SAR imagery, and some groups improved the radar system. By presenting these difficult topics at a high level while at the same time making a radar kit and performing field experiments, students became self motivated to explore these topics and much interest in radar design was generated.
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Summary

MIT Lincoln Laboratory sponsored a radar short course at MIT campus during the January 2011 Independent Activities Period (IAP). The objective of this course was to generate student interest in applied electromagnetics, antennas, radio frequency (RF) electronics, analog circuits, and signal processing by building a short-range radar sensor and using...

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Coherent beam combining of large number of PM fibres in 2-D fibre array

Published in:
Electron. Lett., Vol. 42, No. 18, 31 August 2006, pp. 17-18.

Summary

Coherent combining of a record 48 PM fibres in a phased array configuration is reported. The resulting Strehl ratio degrades by
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Summary

Coherent combining of a record 48 PM fibres in a phased array configuration is reported. The resulting Strehl ratio degrades by

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