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Infrared frequency selective surfaces fabricated using optical lithography and phase-shift masks

May 29, 2001
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Conference Paper
Author:
Steven Jay Spector
…
Published in:
J. Vac. Sci. Technol. B, Vol. 19, No. 6, November/December 2001, pp. 2757-2760. (45th Int. Conf. on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN), 29 May-1 June 2001.)
Topic:
lithography
R&D area:
R&D group:

Summary

A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light's incident angle. The fabrication of the FSS was done using optical lithography and a phase-shift mask. The FSS cell consisted of circular slits spaced by 1100 nm. The diameter and width of the circular slits were 870 and 120 nm, respectively. The FSS was predicted to pass wavelengths near 7 um and reflect wavelengths outside of this pass band. The FSSs fabricated performed as expected with a pass band centered near 5 um.
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Summary

A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light's...

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Infrared frequency selective surfaces fabricated using optical lithography and phase-shift masks

Speaker indexing in large audio databases using anchor models

May 7, 2001
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Conference Paper
Author:
Douglas E. Sturim
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Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 1, 7-11 May 2001, pp. 429-432.
Topic:
speaker recognition
R&D area:
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Summary

This paper introduces the technique of anchor modeling in the applications of speaker detection and speaker indexing. The anchor modeling algorithm is refined by pruning the number of models needed. The system is applied to the speaker detection problem where its performance is shown to fall short of the state-of-the-art Gaussian Mixture Model with Universal Background Model (GMM-UBM) system. However, it is further shown that its computational efficiency lends itself to speaker indexing for searching large audio databases for desired speakers. Here, excessive computation may prohibit the use of the GMM-UBM recognition system. Finally, the paper presents a method for cascading anchor model and GMM-UBM detectors for speaker indexing. This approach benefits from the efficiency of anchor modeling and high accuracy of GMM-UBM recognition.
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Summary

This paper introduces the technique of anchor modeling in the applications of speaker detection and speaker indexing. The anchor modeling algorithm is refined by pruning the number of models needed. The system is applied to the speaker detection problem where its performance is shown to fall short of the state-of-the-art...

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Speaker indexing in large audio databases using anchor models

ASR-9 Processor Augmentation Card (9-PAC) phase II scan-scan correlator algorithms

April 26, 2001
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Project Report
Author:
Robert D. Grappel
Published in:
MIT Lincoln Laboratory Report ATC-298
Topic:
algorithms
R&D area:
R&D group:

Summary

This report documents the scan-scan correlator (tracker) algorithm developed for Phase II of the ASR-9 Processor Augmentation Card (9-PAC) project. The improved correlation and tracking algorithms in 9-PAC Phase II decrease the incidence of false-alarm tracks and increase the detection of real aircraft. The tracker processing for 9-PAC Phase II defined in this document builds upon the prototype 9-PAC Phase II tracker describedin ATC-245. Tracker algorithms from Mode S (ATC-65) are also used in Phase II. This document describes the three main processing tasks of the tracker: initialization, input/output, and the actual correlation/tracking. The tracker itself is further broken down into four main functions: report-to-track association, report-to-track correlation, track update, and track initiation. Each of these functions is described in detail and is further broken down into sub-functions. In addition to the algorithm descriptions, the 9-PAC Phase II tracker system requirements are reviewed, and main data structures used in the 9-PAC Phase II tracker are defined.
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Summary

This report documents the scan-scan correlator (tracker) algorithm developed for Phase II of the ASR-9 Processor Augmentation Card (9-PAC) project. The improved correlation and tracking algorithms in 9-PAC Phase II decrease the incidence of false-alarm tracks and increase the detection of real aircraft. The tracker processing for 9-PAC Phase II...

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ASR-9 Processor Augmentation Card (9-PAC) phase II scan-scan correlator algorithms

Interlingua-based broad-coverage Korean-to-English translation in CCLINC

March 18, 2001
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Conference Paper
Author:
Young-Suk Lee
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Published in:
Proc. First Int. Conf. on Human Language Technology, 18-21 March 2001.
Topic:
machine translation
R&D area:
R&D group:

Summary

At MIT Lincoln Laboratory, we have been developing a Korean-to-English machine translation system CCLINC (Common Coalition Language System at Lincoln Laboratory). The CCLINC Korean-to-English translation system consists of two core modules, language understanding and generation modules mediated by a language neutral meaning representation called a semantic frame. The key features of the system include: (i) Robust efficient parsing of Korean (a verb final language with overt case markers, relatively free word order, and frequent omissions of arguments). (ii) High quality translation via word sense disambiguation and accurate word order generation of the target language. (iii) Rapid system development and porting to new domains via knowledge-based automated acquisition of grammars. Having been trained on Korean newspaper articles on "missiles" and "chemical biological warfare," the system produces the translation output sufficient for content understanding of the original document.
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Summary

At MIT Lincoln Laboratory, we have been developing a Korean-to-English machine translation system CCLINC (Common Coalition Language System at Lincoln Laboratory). The CCLINC Korean-to-English translation system consists of two core modules, language understanding and generation modules mediated by a language neutral meaning representation called a semantic frame. The key features...

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Interlingua-based broad-coverage Korean-to-English translation in CCLINC

The use of dynamic segment scoring for language-independent question answering

March 18, 2001
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Conference Paper
Author:
Daniel J. Pack
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Published in:
Proc. 1st Int. Conf. on Human Language Technology Research, HLT, 18-21 March 2001.
Topic:
machine translation
R&D area:
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Summary

This paper presents a novel language-independent question/answering (Q/A) system based on natural language processing techniques, shallow query understanding, dynamic sliding window techniques, and statistical proximity distribution matching techniques. The performance of the proposed system using the latest Text REtrieval Conference (TREC-8) data was comparable to results reported by the top TREC-8 contenders.
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Summary

This paper presents a novel language-independent question/answering (Q/A) system based on natural language processing techniques, shallow query understanding, dynamic sliding window techniques, and statistical proximity distribution matching techniques. The performance of the proposed system using the latest Text REtrieval Conference (TREC-8) data was comparable to results reported by the top...

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The use of dynamic segment scoring for language-independent question answering

Architectural trades for an advanced geostationary atmospheric sounding instrument

March 10, 2001
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Conference Paper
Author:
Michael E. MacDonald
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Published in:
2001 IEEE Aerospace Conf. Proc., Vol. 4, 10-17 March 2001, pp. 4-1693 - 4-1711.
Topic:
remote sensing
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R&D group:

Summary

The process of formulating a remote sensing instrument design from a set of observational requirements involves a series of trade studies during which judgments are made between available design options. The outcome of this process is a system architecture which drives the size, weight, power consumption, cost, and technological risk of the instrument. In this paper, a set of trade studies are described which guided the development of a baseline sensor design to provide vertical profiles (soundings) of atmospheric temperature and humidity from future Geostationary Operational Environmental Satellite (GOES) platforms. Detailed trade studies presented include the choice between an interferometric versus a dispersive spectrometer, the optical design of the IR interferometer and visible imaging channel, the optimization of the instrument spatial response, the selection of detector array materials, operating temperatures, and array size, the thermal design for detector and optics cooling, and the electronics required to process detected interferograms into spectral radiance. The trade study process was validated through simulations of the radiometric performance of the instrument, and through simulated retrievals of vertical profiles of atmospheric temperature and humidity. The flexibility of these system trades is emphasized, highlighting the differing outcomes that occur from this process as system requirements evolve. Observations are made with respect to the reliability and readiness of key technologies. The results of this study were disseminated to industry to assist their interpretation of, and responses to, system requirements provided by the U.S. Government.
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Summary

The process of formulating a remote sensing instrument design from a set of observational requirements involves a series of trade studies during which judgments are made between available design options. The outcome of this process is a system architecture which drives the size, weight, power consumption, cost, and technological risk...

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Architectural trades for an advanced geostationary atmospheric sounding instrument

MEMS microswitches for reconfigurable microwave circuitry

March 1, 2001
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Journal Article
Author:
Sean M. Duffy
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Published in:
IEEE Microw. Wirel. Compon. Lett., Vol. 11, No. 3, March 2001, pp. 106-108.
Topic:
antennas
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R&D group:

Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted switches have an impedance ratio of 141:1 from the open to closed state and in the closed position have a series capacitance of 1.2 pF. The capacitively-contacted switches have been measured up to 40 GHz with S(21) less than -0.7 dB across the 5-40 GHz band.
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Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted...

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MEMS microswitches for reconfigurable microwave circuitry

Delay causality and reduction at the New York City airports using terminal weather information systems

February 16, 2001
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Project Report
Author:
Shawn S. Allan
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Published in:
Project Report ATC-291, MIT Lincoln Laboratory
Topic:
weather
R&D area:
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Summary

Adverse weather accounts for the bulk of the aviation delays at the major New York City airports. In this report, we quantify: 1. Aviation delay reduction with an Integrated Terminal Weather System (ITWS) that incorporates the 30-60 minute predictions of convective storms generated by the Terminal Convective Weather Forecast (TCWF) algorithm, 2. Principal causes of aviation delays with the ITWS in operation, and 3. The extent to which the current delays are "avoidable". We find that improved decision making by the New York FAA users of ITWS provides an annual delay reduction of over 49,000 hours per year with a monetary value of over $150,000,000 per year. Convective weather was found to be the leading contributor to delays at Newark International Airport (EWR) between September 1998 and August 2000. It was found that 40% of the arrival delay in this study occurred in association with delay days characterized by convective weather both within and at considerable distances from the New York terminal area. Of the remaining delay, 27% occurred on days characterized by low ceiling/visibility conditions, while 16% occurred on fair weather days with high surface winds. We also concluded that many of the delays which occur with the current ITWS, over $1,500,000 in one case, could be avoided if the ITWS were extended to provide: 1. Predictions of thunderstorm decay, and 2. Predictions of the onset and ending of capacity limiting events such as low ceilings or high surface winds. These delay causality results are very important for studies of the effectiveness of changes made to the U.S. aviation system to reduce delays at airports such as Newark as well as for prioritizing FAA research and development expenditures.
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Summary

Adverse weather accounts for the bulk of the aviation delays at the major New York City airports. In this report, we quantify: 1. Aviation delay reduction with an Integrated Terminal Weather System (ITWS) that incorporates the 30-60 minute predictions of convective storms generated by the Terminal Convective Weather Forecast (TCWF)...

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Delay causality and reduction at the New York City airports using terminal weather information systems

Positive charge in the stratiform cloud of a mesoscale convective system

January 16, 2001
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Journal Article
Author:
Thomas C. Marshall
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Published in:
J. Geophys. Res., Vol. 106, No. D1, 16 January 2001, pp. 1157-1163.
Topic:
weather
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R&D group:

Summary

A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The two positive charge regions are the likely sources of six positive cloud-to-ground flashes with large peak currents (>32 kA) that occurred within 60 km of the balloon during its flight. The amount of charge transferred by three of these positive flashes that made Q bursts is calculated in the range of 97-196 C. Flashes of this sort are known to produce sprites and elves in the mesosphere. The positive charge regions in this stratiform cloud are substantially lower than the 10-km altitude commonly assumed for the positive charge in many sprite modeling studies.
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Summary

A balloon sounding of electric field in the trailing stratiform cloud of a bow echo mesoscale convective system reveals only two substantial in-cloud positive charge regions. These charge regions are located at altitudes of 5.1-5.6 km and 6.4-6.8 km, above the level of 0 degree C at 4.2 km. The...

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Positive charge in the stratiform cloud of a mesoscale convective system

An assessment of the communications, navigation, surveillance (CNS) capabilities needed to support the future Air Traffic Management System

January 10, 2001
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Project Report
Author:
Steven D. Thompson
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Published in:
MIT Lincoln Laboratory Report ATC-295
Topic:
air traffic control
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R&D group:

Summary

The purpose of this study was to assess the Communications, Navigation, and Surveillance (CNS) capabilities needed to support future Air Traffic Management (ATM) functionality in the National Airspace System (NAS). The goal was to determine the most effective areas for research and technical development in the CNS field and to make sure the decision support tools under development match future CNS capabilities. The requirements for future ATM functions were derived from high level operational concepts designed to provide more freedom and flexibility in flight operations and from the Joint Research Project Descriptions (JRPDs) that are listed in the Integrated Plan for Air Traffic Management Research and Technology Development. This work was performed for the FAA/NASA Interagency Air Traffic Management Integrated Product Team.
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Summary

The purpose of this study was to assess the Communications, Navigation, and Surveillance (CNS) capabilities needed to support future Air Traffic Management (ATM) functionality in the National Airspace System (NAS). The goal was to determine the most effective areas for research and technical development in the CNS field and to...

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An assessment of the communications, navigation, surveillance (CNS) capabilities needed to support the future Air Traffic Management System
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