Publications
Automatic English-to-Korean text translation of telegraphic messages in a limited domain
August 5, 1996
Conference Paper
Published in:
Proc. Int. Conf. on Computational Linguistics, 5-9 August 1996, pp. 705-710.
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Summary
This paper describes our work-in-progress in automatic English-to-Korean text; translation. This work is an initial step toward the ultimate goal of text and speech translation for enhanced multilingual and multinational operations. For this purpose, we have adopted an interlingual approach with natural language understanding (TINA) and generation (GENESIS) modules at the core. We tackle the ambiguity problem by incorporating syntactic and semantic categories in the analysis grammar. Our system is capable of producing accurate translation of complex sentences (38 words) and sentence fragments as well as average length (12 words) grammatical sentences. Two types of system evaluation have been carried out: one for grammar coverage and the other for overall performance. For system robustness, integration of two subsystems is under way: (i) a rule-based part-of-speech tagger to handle unknown words/constructions, and (ii) a word-for-word translator to handle other system failures.
Summary
This paper describes our work-in-progress in automatic English-to-Korean text; translation. This work is an initial step toward the ultimate goal of text and speech translation for enhanced multilingual and multinational operations. For this purpose, we have adopted an interlingual approach with natural language understanding (TINA) and generation (GENESIS) modules at...
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Experimental comparison of the radiation efficiency for conventional and cavity backed microstrip antennas
July 21, 1996
Journal Article
Published in:
IEEE Antennas and Propagation Society Intl Symp., 21-26 July 1996.
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Summary
The radiation efficiency of conventional microstrip antennas generally decreases when the substrate thickness or permittivity is increased because of loss to surface waves. However, constructing a metal cavity around the microstrip antenna prevents the surface wave propagation. Thus, the cavity backed microstrip antenna has been predicted to have increased radiation efficiency. In this paper, we compare conventional and cavity backed microstrip patch antennas on substrates with an electrical thickness of 0.067 ho and dielectric constants of ~r=2.94, 6.15, and 10.2. As one would expect, the radiation efficiency of the conventional patch decreases with increasing dielectric constant, but the efficiency remains relatively constant for the cavity backed patch. In this work, three different methods are used to measure the radiation efficiencies: a far field gain comparison, a Wheeler cap method and an input admittance method.
Summary
The radiation efficiency of conventional microstrip antennas generally decreases when the substrate thickness or permittivity is increased because of loss to surface waves. However, constructing a metal cavity around the microstrip antenna prevents the surface wave propagation. Thus, the cavity backed microstrip antenna has been predicted to have increased radiation...
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The COBEL model as part of a terminal-area ceiling & visibility (C&V) nowcast system: a progress report
July 18, 1996
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-241
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of products aimed at providing automated guidance to the air traffic managers for the anticipation of changes in ceiling and visibility (C&V) conditions and wake vortex behavior in the terminal area. Fine-resolution, one-dimensional (column) numerical models are being considered to provide information on the evolution of the local fine-scale structure of the lower atmosphere over the terminal area. The Code Brouillard Eau Liquids (COBEL) column model is being investigated for potential use within the ITWS. This one-dimensional numerical model has been developed for the short-term prediction of fog events in the north of France. This report describes initial progress in adapting the COBEL model to a wider range of meteorological conditions. A parameterization of surface frost deposition was implemented and a slight error in the computation of stability in a saturated atmosphere was corrected. Tests suggest that these modifications represent important features of the newest version of the COBEL model. Other significant modifications to the COBEL model were performed. Pressure tendencies and vertical motion (vertical advection) were implemented as additional external forcings to the column model. Sensitivity tests show that these forcings play important roles in determining the onset, evolution and dissipation of low stratiform clouds. Some further applications of the model are briefly discussed and future development efforts are suggested.
Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of products aimed at providing automated guidance to the air traffic managers for the anticipation of changes in ceiling and visibility (C&V) conditions and wake vortex behavior in the terminal area. Fine-resolution, one-dimensional (column) numerical models...
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Assessment of the delay aversion benefits of the Airport Surveillence Radar (ASR) Weather Systems Processor (WSP)
July 2, 1996
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-249
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Summary
The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show current location and anticipated movement of thunderstorm cells, and provide short-term forecasts of operationally significant wind shifts. Operational tests of a prototype WSP and related terminal area hazardous weather detection systems (the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS)) have shown that, in addition to reducing the risk of aircraft accidents associated with wind shear encounters on landing or takeoff, the information provided by these systems is a significant aid in terminal air traffic management during adverse weather. The resulting efficiency enhancements reduce delay and associated costs. This report assesses the magnitude of the delay aversion benefits that will be realized through national deployment of the WSP. These are quantified both in terms of aircraft delay-hour reductions and corresponding dollar benefits. The analysis indicates that these benefits will total approximately $18M per year given year 2000 expected traffic counts at the 34 planned WSP airports. This exceeds, in equivalent dollar value, the safety benefits realized through WSP deployment by a factor of approximately five.
Summary
The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show...
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The Marine Stratus Initiative at San Francisco International Airport
June 25, 1996
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-252
Summary
San Francisco International Airport is one of the busiest airports in the United States and one of the highest delay airports in terms of total aircraft delay hours and number of imposed air traffic delay programs. As with most airports, weather is the primary cause of aircraft delay. In particular, the local airspace is prone to regular occurrences of low cloud ceiling conditions due to intrusion of marine air from the eastern Pacific Ocean from May through September. Typically, this layer of stratus clouds forms in the San Francisco Bay area overnight and dissipates during the middle to late morning. The timing of the stratus cloud dissipation is such that it frequently poses a threat to the morning arrival push of air traffic into San Francisco. Weather forecasters at the Central Weather Service Unit (CWSU) at the Oakland AirRoute Traffic Control Center are responsible for providing a forecast whether or not the cloudiness will impact morning traffic operations. This information is used for decision making by the Traffic Management Unit at Oakland Center in order to optimally match arriving traffic demand to available airport capacity. As part of the FAA's Integrated Terminal Weather System, the Weather Sensing Group at MIT Lincoln Laboratory has begun an effort entitled the "Marine Stratus Initiative." Its objective is to provide improved weather information and forecast guidance to the Oakland CWSU, which is responsible for providing weather forecasts to air traffic managers. During 1995, the main focus of the project was the design and implementation of a data acquisition, communication, and display infrastructure that provides forecasters with new sources of weather data and information. These initial capabilities were tested during an operational demonstration in August and September. As the project continues, the intent is to improve these new data sources and develop an automated or semi-automated algorithm that will process raw information to provide weather forecasters with numerical guidance to assist them in the forecast process. A description of airport operations at San Francisco and the impact of marine stratus are presented. An explanation is given of the marine stratus phenomenology and the primary factors contributing to cloud dissipation. This conceptual model of the dissipation process is used to define system requirements. A description of the hardware, communications, and display subsystems is provided. An overview of the 1995 demonstration, including user comments, is presented, as well as future plans for meeting the longer-term objectives of the project.
Summary
San Francisco International Airport is one of the busiest airports in the United States and one of the highest delay airports in terms of total aircraft delay hours and number of imposed air traffic delay programs. As with most airports, weather is the primary cause of aircraft delay. In particular...
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Air Force planetary defense system: initial field test results
June 1, 1996
Conference Paper
Published in:
Proc. of the Fifth Int. Conf. on Space '96: Engineering, Construction, and Operations in Space V, 1-6 June 1996, pp. 46-53.
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Summary
Over the past several years, the Air Force has been developing new devices and technology for the detection and tracking of earth orbiting satellites. This technology has been targeted to provide an upgraded capability for an operational space surveillance system called GEODSS. Currently, a number of GEODSS systems are deployed around the world as part of the world-wide space surveillance system operated by the US Air Force. Each GEODSS site is currently equipped with 1-meter class telescopes and EBSICON detector systems which represent 1970's technology. The Air Force is now in the process of upgrading the GEODSS system to achieve the performance offered by state of the art detector systems. Under Air Force sponsorship, Lincoln Laboratory has developed a new generation of sensitive, large format, frame transfer CCD focal planes for GEODSS. These focal planes have been installed in a new generation of cameras and are currently undergoing testing at the Lincoln Laboratory Experimental Test Site (ETS). When equipped with the new focal plane and camera technology, the modest sized GEODSS telescopes have considerable capability to conduct large coverage, sensitive searches for earth crossing asteroids. Theoretical analysis has indicated that the CCD equipped GEODSS telescope will be capable of achieving a limiting magnitude of 22, over a 2 sq/deg field of view, with about 100 seconds of integration. This is comparable to the sensitivity of considerably larger telescopes equipped with current cameras. In addition to the high sensitivity, the CCD is configured for frame transfer operations which are well suited to asteroid search operations. This paper will present the results of the initial system tests conducted at the ETS and will discuss how this technology fits into a concept of operations for a planetary defense system based on the Air Force developed technology.
Summary
Over the past several years, the Air Force has been developing new devices and technology for the detection and tracking of earth orbiting satellites. This technology has been targeted to provide an upgraded capability for an operational space surveillance system called GEODSS. Currently, a number of GEODSS systems are deployed...
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Six-sector antenna for the GPS-squitter en-route ground station
May 31, 1996
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-248
Summary
Summary: A six-sector antenna for a pole-mounted GPS-Squitter en-route ground station was designed, built, and tested. The fan beam of each of the six sectors of the antenna covers a 60- degree azimuthal sector. Together, the six uniformly-spaced, contiguous 60-degree sectors cover the complete 360 degrees of azimuth at the two Mode S frequencies, 1030 and 1090 MHz. When equipped with its receivers, the antenna achieves a maximum operational squitter reception range in excess of 200nmi. Physically, the antenna consists of six vertical 12-element linear arrays spaced uniformly round the circumference of an imaginary vertical circular cylinder and lying parallel to its axis. Six reflectors in the form of parabolic cylinders are mounted behind the linear arrays, one per array, to define the six separate sector beams. The complete radome-enclosed assembly is a cylinder eight feet tall and 23 inches in diameter. It weighs 250 pounds.
Summary
Summary: A six-sector antenna for a pole-mounted GPS-Squitter en-route ground station was designed, built, and tested. The fan beam of each of the six sectors of the antenna covers a 60- degree azimuthal sector. Together, the six uniformly-spaced, contiguous 60-degree sectors cover the complete 360 degrees of azimuth at the...
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Improving wordspotting performance with artificially generated data
May 9, 1996
Conference Paper
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech, and Signal Processing, ICASSP, 9 May 1996, pp. 526-9.
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Summary
Lack of training data is a major problem that limits the performance of speech recognizers. Performance can often only be improved by expensive collection of data from many different talkers. This paper demonstrates that artificially transformed speech can increase the variability of training data and increase the performance of a wordspotter without additional expensive data collection. This approach was shown to be effective on a high-performance whole-word wordspotter on the Switchboard Credit Card database. The proposed approach used in combination with a discriminative training approach increased the Figure of Merit of the wordspotting system by 9.4% percentage points (62.5% to 71.9%). The increase in performance provided by artificially transforming speech was roughly equivalent to the increase that would have been provided by doubling the amount of training data. The performance of the wordspotter was also compared to that of human listeners who were able to achieve lower error rates because of improved consonant recognition.
Summary
Lack of training data is a major problem that limits the performance of speech recognizers. Performance can often only be improved by expensive collection of data from many different talkers. This paper demonstrates that artificially transformed speech can increase the variability of training data and increase the performance of a...
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Low rate coding of the spectral envelope using channel gains
May 7, 1996
Conference Paper
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 2, 7-10 May 1996, pp. 769-772.
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A dual rate embedded sinusoidal transform coder is described in which a core 14th order allpole coder operating at 2400 b/s is augmented with a set of channel gain residuals in order to operate at the higher 4800 b/s rate. The channel gains are a set of non-uniformly spaced samples of the spline envelope and constitute a lowpass estimate of the short-time vocal tract magnitude spectrum. The channel gain residuals represent the difference between the spline envelope and the quantized 14th order allpole spectrum at the channel gain frequencies. The channel gain residuals are coded using pitch dependent scalar quantization. Informal listening indicates that the quality of the embedded coder at 4800 b/s is comparable to that of an existing high quality 4800 b/s allpole coder.
Summary
A dual rate embedded sinusoidal transform coder is described in which a core 14th order allpole coder operating at 2400 b/s is augmented with a set of channel gain residuals in order to operate at the higher 4800 b/s rate. The channel gains are a set of non-uniformly spaced samples...
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The effects of handset variability on speaker recognition performance: experiments on the switchboard corpus
May 7, 1996
Conference Paper
Published in:
Proc. IEEE Int. Conf. on Acoustics, Speech and Signal Processing, ICASSP, Vol. 1, 7-10 May 1996, pp. 113-116.
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Summary
This paper presents an empirical study of the effects of handset variability on text-independent speaker recognition performance using the Switchboard corpus. Handset variability occurs when training speech is collected using one type of handset, but a different handset is used for collecting test speech. For the Switchboard corpus, the calling telephone number associated with a file is used to imply the handset used. Analysis of experiments designed to focus on handset variability on the SPIDRE database and the May95 NIST speaker recognition evaluation database, show that a performance gap between matched and mismatched handset tests persists even after applying several standard channel compensation techniques. Error rates for the mismatched tests are over 4 times those for the matched tests. Lastly, a new energy dependent cepstral mean subtraction technique is proposed to compensate for nonlinear distortions, but is not found to improve performance on the databases used.
Summary
This paper presents an empirical study of the effects of handset variability on text-independent speaker recognition performance using the Switchboard corpus. Handset variability occurs when training speech is collected using one type of handset, but a different handset is used for collecting test speech. For the Switchboard corpus, the calling...
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