Showing papers by "Mitre Corporation published in 1985"

A Visual Model Weighted Cosine Transform for Image Compression and Quality Assessment

Abstract: Utilizing a cosine transform in image compression has several recognized performance benefits, resulting in the ability to attain large compression ratios with small quality loss. Also, incorporation of a model of the human visual system into an image compression or quality assessment technique intuitively should (and has often proven to) improve performance. Clearly, then, it should prove highly beneficial to combine the image cosine transform with a visual model. In the past, combining these two has been hindered by a fundamental problem resulting from the scene alteration that is necessary for proper cosine transform utilization. A new analytical solution to this problem, taking the form of a straightforward multiplicative weighting function, is developed in this paper. This solution is readily applicable to image compression and quality assessment in conjunction with a visual model and the image cosine transform. In the development, relevant aspects of a human visual system model are discussed, and a refined version of the mean square error quality assessment measure is given which should increase this measure's utility.

Computing the discrete Fourier transform using residue number systems in a ring of algebraic integers

Abstract: A new method is described for computing an N = R^{m} = 2^{\upsilon m} -point complex discrete Fourier transform that uses quantization within a dense ring of algebraic integers in conjunction with a residue number system over this ring The algebraic and analytic foundations for the technique are derived and discussed The architecture for a radix- R fast Fourier transform algorithm using a residue number system over Z[\omega] , where \omega is a primitive R th root of unity, is developed; and range and error estimates for this algorithm are derived

Instantaneous-frequency distribution vs. time: An interpretation of the phase structure of speech

Abstract: A new time-frequency display is constructed based on the phase of the running short-time Fourier transform, specifically the distribution of its time derivative. Typical results are given for speech, indicating more precise location of formants than is usual for the spectrogram.

Active star centered fiber optic local area network

Abstract: The local area optical network interconnects a plurality of user terminals. The local area network includes an interface unit for receiving information from the user terminals and an active star node connected to the interface unit by fiber optic cables. In one embodiment, the active star centered node includes a passive optical star coupler having a plurality of ports for interconnecting the terminals. An optical receiver receives optical signals from the star coupler and is interconnected with an optical transmitter which transmits the signal from the receiver back into the star for distribution to the plurality of ports. In either embodiment, the star node includes an expansion port and an optically associated transmitter and receiver to allow multiple nodes to be connected to one another in an hierachial, branching architecture. In another embodiment, the active star centered node includes a passive input star coupler and a passive output star coupler. The local area networks organized around the active stars are portable, flexible and expandable.

Information-seeking behavior in an applied research/service delivery setting

Abstract: The area of rural mental health services was used as a testbed to study information-seeking behavior in a field that includes researchers, policymakers, and practitioners. Findings from a nationwide survey (n = 1666) describe the sources that were used to obtain information about various topics and the use and value of these sources by or to individuals in various work roles and settings. The findings demonstrate the importance of person-to-person communication; differences in the sources used, and the value placed on these sources, by individuals in different work roles and settings; and that information-seeking episodes generally involve using multiple sources (5.0) to obtain information about several topics (3.2).

Voiced/Unvoiced decision based on the bispectrum

Abstract: We initiate an analysis of English phonemes using the bispectrum. The first part of our work demonstrates that fricative phonemes share a certain statistical property with Gaussian data not shared by purely voiced phonemes. Namely, approximations to the bispectra of fricative phonemes tend to zero, whereas, approximations to the bispectra of voiced phonemes do not. Indeed, the bispectra of voiced phonemes have complex structure as seen from their log-magnitude plots. A Fortran program based on the above principle processes speech filtered to 4 kHz and sampled at 8 kHz. Each 180 sample (22 ms.) block is declared to be voiced, unvoiced, or silent. In addition, a numerical measure of the mixed excitation is given. An advantage of this method over conventional ones is that it is less subject to noise interference.

A fault detection and isolation method applied to liquid oxygen loading for the space Shuttle

Abstract: Process-monitoring and fault location techniques have been developed at the Kennedy Space Center in a domain of mixed media control in NASA's Space Shuttle Launch Processing System. An intuitively appealing diagnostic technique and representation of the system's structure and function were formulated in cooperation with system engineers. Functional relationships that determine the consistency of sensor measurements are represented by symbolic expressions embedded in frames. Functional relationships are stored in exactly one place, so they must be inverted to determine hypothetical values for possibly faulty objects. Propagating these hypothetical states to other sensors permits the location of faults. Standard symbolic inversion techniques have been extended to include conditional functions. A demonstration system is operating, and its evaluation will soon use live data from the firing rooms at KSC.

Design Overview for Retrofitting Integrity-Lock Architecture onto a Commercial DBMS

Abstract: This paper is a design overview document, intended to aid in the implementation of an integrity-lock database management system. The authors believe that the paper is a realistic overview of the changes that need to be made to a commercial database management system in order that may support the integrity-lock architecture. The paper examine the integrity-lock retrofit at a high level of abstraction. In particular it concentrates on changes that need to be made at the process level and in terms of the functionality that needs to reside in the various functions. It hoped that this high level view will aid in the portability of the integrity-lock architecture to other systems. While the authors' work has involved retrofitting the integrity-lock onto a specific system, we believe that many of the lessons learned in this exercise can be applied to other commercial database management systems.

Applications of digital technology to radar

Abstract: Digital technology permeates electronic design, especially in the field of radar. This paper describes some ways in, which digital technology is used to overcome the limits of analog circuits, particularly in waveform generation, signal processing, and clutter suppression. Another example of the application of digital technology to radar is the general-purpose computer that is part of every modern radar. The ability of state-of-the-art computers to support radar requirements is surveyed, and future capabilities are projected.

Satellite Selection Criteria During Altimeter Aiding of GPS

Abstract: The 21 satellite constellation envisaged for GPS yields occasional geometric configurations that result in poor navigation solutions. It therefore may be necessary to use altimeter aiding in these cases in order to improve the geometry. During altimeter aiding, only three of the visible satellites will be used in conjunction with the altimeter. It is of paramount importance to select the three satellites that will yield the best possible navigation solution when combined with the altimeter data. This paper presents a closed form algorithm for satellite selection. It differs from other satellite selection algorithms in that they use four visible satellites and do not consider the altimeter. Also, the usual problem of computationally inverting a 4 × 4 matrix is avoided. Computer simulations show that the algorithm avoids selecting any of the satellite configurations that would yield a poor navigation solution. A comparison has been made between using the true GDOP closed form solution and the maximum volume of a tetrahedron. The latter is shown to be an integral part of the former. Results indicate that it yields sufficiently accurate results under the assumed conditions.

Learning by discovering macros in puzzle solving

Abstract: This paper proposes a model of learning by discovery. The model consists of a program which discovers macro operators while conducting a best first heuristic search in the domain of puzzles. This work extends some recent work on permutation puzzles (Korf, 1982) and operator-decomposable puzzles (Korf, 1983), and is related to the earlier work on MACROPS (Fikes, Hart, and Nilsson, 1972). This work is part of a doctoral dissertation currently in progress at MIT, in which the model will be used to explore learning in conjunction with additional search paradigms and numerous alternative heuristics for macro generation and selection. The specific heuristic reported on here is that of using peaks of the evaluation function to segment the paths of the search tree in order to discover macros. The technique seems particularly valuable in difficult puzzles where only imperfect or approximate evaluation functions ar available.

Gps integrity channel

Abstract: This paper documents a system description and operational concept for ensuring the integrity of the Global Positioning System (GPS) signals-in-space for use in the National Airspace System. The concept employs a ground monitoring network, L-band transponders placed onboard already planned geostationary communication satellites to broadcast integrity data, and an integrated receiver containing both the GPS and the GPS Integrity Channel (GIC). The three, aforementioned system segments are described. The feasibility of employing a network of only four ground monitors to cover CONUS is analyzed. A discussion concerning implementation of such a system is also presented.

The transfer of polarized radiation in spectral lines: Formalism and solutions in simple cases

Abstract: A general treatment of the transfer of polarized radiation in spectral lines assuming a Rayleigh phase function and a general law of frequency redistribution is derived. It is shown how nine families of coupled integral equations for the moments of the radiation field arise which are necessary to fully describe the state of polarization of the emergent radiation from a plane-parallel, semi-infinite atmosphere. The special case of angle independent redistribution functions is derived from the general formalism, and it is shown how the nine families of integral equations reduce to the six linearly independent integral equations derived by Collins (1972). To serve as a test of the formulation, solutions for isothermal atmospheres are given.

Measurement of Ocean Surface Currents from Space with Multifrequency Microwave Radars-A System Analysis

Abstract: The use of multifrequency microwave radars to measure ocean surface currents from satellites is considered in this paper. We discuss the effects that satellite motion background backscatter from the ocean surface, and receiver noise have on the ability of such systems to obtain current maps. We present an example which shows that radars in geostationary orbit have the potential to map ocean currents over large areas of the ocean surface.

Application of Guidelines for Designing User Interface Software

Abstract: A survey was conducted of people who had received a report on guidelines for designing user interface software. Analysis of questionnaire responses indicates that design guidelines are generally considered useful, but that there are significant problems in the practical application of guidelines. For effective application, generally stated guidelines must be translated into system-specific design rules.

Person-to-person communication in an applied research/service delivery setting

Abstract: Data from a national survey (n = 1666) of researchers, practitioners, and policymakers in the field of rural mental health services were used to conduct a sociometric analysis of person-to-person communication in tData from a national survey (n = 1666) of researchers, practitioners, and policymakers in the field of rural mental health services were used to conduct a sociometric analysis of person-to-person communication in tData from a national survey (n = 1666) of researchers, practitioners, and policymakers in the field of rural mental health services were used to conduct a sociometric analysis of person-to-person communication in the field. This article describes the structure of the person-to-person communication network in terms of its connectedness, centrality, homogeneity, and differentiation. Despite the diversity of survey respondents, and apparently meager interorganizational communication, communication in the field is similar, in many respects, to that observed in “invisible colleges.” While the probability of two randomly chosen individuals being in contact is low (0.0008), over 70% were connected indirectly. The person-to-person communication network is also highly centralized and exhibits higher than expected communication among respondents in the same professional role, type of work organization, and geographical region. It does not appear to be highly differentiated with respect to topic, since the majority of information providers are contacted with respect to a number of topi While the probability of two randomly chosen individuals being in contact is low (0.0008), over 70% were connected indirectly. The person-to-person communication network is also highly centralized and exhibits While the probability of two randomly chosen individuals being in contact is low (0.0008), over 70% were connected indirectly. The person-to-person communication network is also highly centralized and exhibits higher than expected communication among respondents in the same professional role, type of work organization, and geographical region. It does not appear to be highly differentiated with respect to topic, since the majority of information providers are contacted with respect to a number of topics.

The Impact of Cross-Rate Interference on LORAN-C Receivers

Abstract: Wong [1] recommends that 16 additional LORAN-C ground stations are needed to provide redundant coverage throughout the conterminous U.S. so that LORAN-C can provide the primary navigation service to civil aviation. The purpose of this paper is to estimate the effect of the interference from the additional stations on the acquisition (phase code identification and third cycle selection) and track modes of a LORAN-C receiver whose detection process is based on the sequential decision theory. This receiver model represents a modern design using microprocessor technology. The results are compared against the requirement that acquisition be completed 90 percent of the time within 7.5 minutes. The impact of cross-rate interference (CRI) on the track mode is estimated using a time-domain analysis.

Design and Hardware Implementation of a Versatile Transform Decoder for Reed-Solomon Codes

Abstract: The design and hardware implementation of a versatile Reed-Solomon encoder and decoder based on a transform decoding algorithm is presented. The decoder is electronically reconfigurable to accommodate a large number of different code parameters; the symbol fields range from 4 to 8 bits, the code lengths range from 3 to 255 symbols, and the rates are programmable downward to a minimum of one-half. The discrete transform used for encoding and syndrome computation is implemented with an algorithm that minimizes the number of extension-field products. The error locator uses a modified version of the Berlekamp-Massey feedback shift register synthesis algorithm to correct both errors and erasures. In the decoder’s implementation, extension-field operations are separated to a maximum extent from the normal binary operations to promote reconfiguration. The decoding algorithm results in a highly repetitive architecture intended for VLSI implementation. This VLSI architecture is described in detail. The design and measured performance of a TTL breadboard and key-function VLS I macrocells that have been implemented as custom designed LSI circuits are described.

A knowledge based expert system for propellant system monitoring at the Kennedy Space Center

Abstract: The Lox Expert System (LES) is the first attempt to build a realtime expert system capable of simulating the thought processes of NASA system engineers, with regard to fluids systems analysis and troubleshooting. An overview of the hardware and software describes the techniques used, and possible applications to other process control systems. LES is now in the advanced development stage, with a full implementation planned for late 1985.

Issues in software reusability

Abstract: At the ACM SIGAda Future Ada Environments Workshop, the working group on software reusability decided that the most productive use of the little time available to the group was to clearly determine the issues in software reusability and make recommendations wherever possible.

Observations on Operating a LocaI Area Network

Abstract: Local area networks have become part of the information infrastructure. A few years ago they were technical innovations; today they are an established technology-which is being challenged. There are sufficient numbers of LAN products on the market, installed, and in use to permit observations on their strengths and weaknesses. This discussion of local area networking adopts a service viewpoint. LANs utilize certain services (e.g., a broadband LAN* utilizes a CATVtype cable plant as its distribution and connectivity service) and provide additional services. The term often applied to this concept is "value added," which implies that each level of service provided employs some other level of service as input, adds something to it, and provides an enhanced level of service as output. To the casual observer this is a continuous process; there is no "basic" service and no "enhanced" service since each level is built on all preceding levels. Put another way, one observer's system is another observer's component. This view of services is similar

Grammatical relations as the basis for natural language parsing and text understanding

Abstract: The KING KONG parser described by this paper attempts to apply the principles of relational grammar to the parsing of English in older to overcome the problems encountered by syntactic and semantic parsers. Specifically, this-parser uses relational categories such as subject, direct object, and instrument to map syntactic constituents onto semantic roles with in CD-like structures. Thus, the parser makes use of both syntactic and semantic information to guide its parse.

Trusted Software Verification: A Case Study

Abstract: This paper presents a case study of the verification of the trusted software component of the SCOMP system Trusted Computing Base (TCB). The SCOMP system was developed by Honeywell and is the first system to achieve an A1 rating from the DoDCSC. A number of papers have been published that discuss the verification approach for the SCOMP system security kernel [15, 14, 12, 10]. The SCOMP system security kernel was verified using the Hierarchical Development Methodology in a manner similar to those used for previous kernel verifications [13]. Most of the research and applications to date have been directed towards verifying the security properties of kernel software. Much less is known about verifying the security properties of trusted software. This paper will present a case study of these trusted software verification in the SCOMP system. The case study will focus on defining what trusted software is in a kernelized systems, why trusted software is trusted, what are the security requirements to be proved, and how should these requirements be proven. Then a method developed at MITRE for the review of trusted software werification evidence using the Gypsy methodolgy will be presented. Finaly, area requiring futher research will be discussed.

Color Coding Re-Viewed

Abstract: The advantages and disadvantages of color coding in information displays are summarized, based on the available experimental data. The necessity of analyzing the observers task in making decisions about the application of color to displays is stressed. Nevertheless, it is shown that if certain conditions are met as to luminance, subtense and chromaticity of the light signals, all normal observers and a majority of color-deficient observers can make the necessary identifications to aid performance. Recommendations are made for the effective use of color in complex information displays.

Estimates for the stability of low-pass filters

Abstract: A measure of stability is defined for digital filters. It is shown that the stability of low-pass filters goes to zero as the filter characteristics approach that of an ideal low-pass filter. More precisely, estimates for the rate of convergence are given. It is shown that, except for constants, the stability of a low-pass filter is no greater than the square root of the reciprocal of the logarithm of the transition bandwidth. For linear phase filters the square root may be removed. These estimates are shown to be optimal for the case of linear phase filters.

A Note on Contention with Reference to Communication Networks

Abstract: In this paper we give a solution to a contention problem with reference to communication networks. A and B simultaneously try to access a communication channel. They attempt access again at some later time chosen at random. From what probability density function should the time be chosen to minimize conflict? They are not allowed to communicate with one another.