Showing papers by "Mitre Corporation published in 1977"

Information processing

Abstract: One dilemma with health claims is that too much information can confuse consumers and too little information can mislead them. Instead of using only one side of the package, a laboratory study is used to examine the effectiveness of various front-sided health claims when used in combination with a full health claim on the back panel. The results indicate that the presence of a short health claim on the front label generates more specific attribute-related thoughts, more inferences, and creates a more believable and positive image of the product in the consumers’ mind than does a longer health claim on the front label. This article concludes with a discussion of how labeling information needs to be presented to effectively allow consumers to understand and use claim information.

History of automatic vehicle monitoring (AVM)

Abstract: The development of automatic vehicle monitoring (AVM) technology is traced from the PULSE conference of 1968 to the present. Examples of nonautomated vehicle monitoring from the past and present are cited along with a glimpse of the improvements that AVM promises. A perspective for the current AVM development activities is provided.

A Worst-Case Crosstatk Comparison Among Several Modulation Schemes

Abstract: The effects of worst-case crosstalk (from a time-domain point of view) on unsynchronized frequency division multiplexed (FDM) constant envelope modulations are considered assuming coherent hard-decision receivers and no filtering for bandwidth constraint. Continuous-phase frequency shift keying (FSK) is found to be superior to various forms of phase shift keying (PSK).

Effects of a Hard Limiting Repeater on the Performance of a DPSK Data Transmission System

Abstract: Although the effects of a hard-limiting repeater on coherent phase shift keying (CPSK) data transmission systems have been studied, corresponding effects pertaining to differential phase shift keying (DPSK) systems are yet to be examined. The present paper contains the results of a study on DPSK data detection performance when a hard-limiting repeater is part of the overall data link under consideration, and white Gaussian noise is introduced at the repeater and receiver front ends; the extension to the multi-link system, containing cascaded hard-limiting repeaters, is also included. The results obtained were found to be analogous to those of previous CPSK studies. Specifically, the inclusion of the hard-limiter was generally shown to improve probability of error performance when downlink noise is present. A comparison of present results with those of previous ones for corresponding CPSK systems shows that DPSK is degraded noticeably more by downlink noise than its CPSK counterpart.

Frequency-Domain Interference Excising at Radio Frequencies

Abstract: A simple interference excising algorithm was employed to remove discrete narrow-band interferers from wide-band radio frequency noise measurements made in the North Atlantic during three seasons of the year. Narrow-band signals were reduced by 9 to 18 dB in average data samples with only 5 to 25 percent of the effective bandwidth being sacrificed. Both the amount of bandwidth and interference power excised from samples of data were found to increase as the spectral resolution used in the excising process was increased. (The amount of interference power removed was still increasing at the narrowest spectral resolution of 122 Hz utilized.) It was concluded that frequency-domain-excising techniques can be employed to advantage in lowering the effective interference level for spread-spectrum system signal processing.

Fluidized-Bed Combustion Technology—A Review

Abstract: Fluidized-bed combustion of coal is now recognized as an economically viable process with a great potential to enhance coal utilization and thereby lessen the ever increasing burden on the scarce p...

A novel concept for a satellite-based maritime search and rescue system

Abstract: Search and rescue (SAR) for both airborne and maritime vehicles has been an area of intense investigation for many years. Current techniques include employment of small distress transmitters which provide signals that have only a limited interception capability. This can considerably increase the search time and reduce its effectiveness. With the increased availability-existing and planned-of both synchronous and nonsynchronous satellites, SAR investigations are being directed toward the application of satellites. The present paper introduces the concept of satellite-based maritime search and rescue system (SAMSARS). This is a proposed pseudonoise (PN) wide-band spread spectrum system that would operate at low power levels and coexist with operational communication satellite systems (voice or data) without mutual interference. The use of existing operational satellite spectrum, instead of a dedicated distress channel or special satellites, is a major feature of SAMSARS. Other important aspects are its capability of providing unique identification and distress information in minutes following activation of the distress transmitter and its inherent immunity to false alarms. SAMSARS can also provide position location directly when three satellites are mutually visible or indirectly, by taking advantage of a vessel's on-board derived navigation data. This paper presents concept elements such as message structure, transmitter and receiver block diagrams, and unique features of SAMSARS. The paper also presents an operational example, including sample link power budgets, and finally specifies areas for further investigation.

Marine radar interrogator-transponder

Abstract: The use of ship's radar for collision avoidance presents a fundamental problem in threat detection and identification since all vessel radar returns ("paints") look alike. As a result, when a ship master caught in a fog is trying to use his radio-telephone to work out a maneuvering plan with another vessel, it is difficult for him to identify which blip on the planar position indicator PPI is the source of the voice on the radio. One solution now receiving worldwide attention is to fit all vessels with active transponders. The marine radar interrogator-transponder (MRIT) is an advanced form of transponder which includes an integral interrogator and works in coordination with the ship radar to provide not only target identity and "clutter-free" target paints, but also maneuvering information and such data as target's course, speed, draft, safe or dangerous cargo, etc. Mounted on a fixed navigation aid, the transponder portion alone can also function as a racon (radar beacon). This paper describes the operational parameter and reviews the system bench tests and sea trials.

The Need for Better Data to Support Crime Control Policy

Abstract: On the one hand, the importance of evaluation findings for crime control policy now appears to be well understood. On the other hand, the contribution of evaluative data to those findings and to that policy seems much less well established. This paper examines some of the weaknesses of the data base presently available for evaluation in the criminal justice area and relates the quality of evaluation findings to the quality of that data support. A case study (the national-level evaluation of the High-Impact Anti-Crime Program) serves to illustrate the points made and to develop recommendations for new efforts needed in this area.

A novel concept for a satellite-based maritime search and rescue system

Abstract: Search and rescue (SAR) for both airborne and maritime vehicles has been an area of intense investigation for many years. Current techniques include employment of small distress transmitters which provide signals that have only a limited interception capability. This can considerably increase the search time and reduce its effectiveness. With the increased availability-existing and planned-of both synchronous and nonsynchronous satellites, SAR investigations are being directed toward the application of satellites. The present paper introduces the concept of satellite-based maritime search and rescue system (SAMSARS). This is a proposed pseudonoise (PN) wide-band spread spectrum system that would operate at low power levels and coexist with operational communication satellite systems (voice or data) without mutual interference. The use of existing operational satellite spectrum, instead of a dedicated distress channel or special satellites, is a major feature of SAMSARS. Other important aspects are its capability of providing unique identification and distress information in minutes following activation of the distress transmitter and its inherent immunity to false alarms. SAMSARS can also provide position location directly when three satellites are mutually visible or indirectly, by taking advantage of a vessel's on-board derived navigation data. This paper presents concept elements such as message structure, transmitter and receiver block diagrams, and unique features of SAMSARS. The paper also presents an operational example, including sample link power budgets, and finally specifies areas for further investigation.

Integral glass encapsulation for solar arrays

Abstract: Work reported was performed during the period from August 1977 to December 1978. The program objective was to continue the development of electrostatic bonding (ESB) as an encapsulation technique for terrestrial cells. Economic analyses shows that this process can be a cost-effective method of producing reliable, long lifetime solar modules. When considered in sufficient volume, both material and equipment costs are competitive with conventional encapsulation systems. In addition, the possibility of integrating cell fabrication into the encapsulation process, as in the case of the preformed cell contacts discussed in this report, offers the potential of significant overall systems cost reduction.

On-board data collection for transit operations

Abstract: Improved techniques for collecting data on transit operations are essential to improvements in transit operating efficiency. An On-Board Data Collection System, which is being developed for use by the transit industry, provides information on ridership, revenue, and mileage. A test program to determine the most suitable automatic passenger counting technique for use in such a system has shown that accuracies of better than 90 percent can be achieved. Mileage and information on revenue collected can be determined to better than 98 percent accuracy. The system provides for data storage on the vehicle, with subsequent off-line data processing.

Determination of scattering functions and their effects on remote sensing of turbidity in natural waters

Abstract: The development of quantitative analytical procedures for relating scattered signals, measured by a remote sensor, was considered. The applications of a Monte Carlo simulation model for radiative transfer in turbid water are discussed. The model is designed to calculate the characteristics of the backscattered signal from an illuminated body of water as a function of the turbidity level, and the spectral properties of the suspended particulates. The optical properties of the environmental waters, necessary for model applications, were derived from available experimental data and/or calculated from Mie formalism. Results of applications of the model are presented.

Effects of a hard limiting repeater on the performance of a DPSK data transmission system

Abstract: Although the effects of a hard-limiting repeater on coherent phase shift keying (CPSK) data transmission systems have been studied, corresponding effects pertaining to differential phase shift keying (DPSK) systems are yet to be examined. The present paper contains the results of a study on DPSK data detection performance when a hard-limiting repeater is part of the overall data link under consideration, and white Gaussian noise is introduced at the repeater and receiver front ends; the extension to the multi-link system, containing cascaded hard-limiting repeaters, is also included. The results obtained were found to be analogous to those of previous CPSK studies. Specifically, the inclusion of the hard-limiter was generally shown to improve probability of error performance when downlink noise is present. A comparison of present results with those of previous ones for corresponding CPSK systems shows that DPSK is degraded noticeably more by downlink noise than its CPSK counterpart.

Performance of a Square Law Pseudonoise Ranging Time-of-Arrival Estimator

Abstract: The performance of a square law time-of-arrival (TOA) estimator that has been proposed for use in ASTRO-DABS, part of a possible satellite-based fourth generation air traffic control system is considered. The transmitted message consists of a pulse amplitude modulated (PAM) ranging sequence that, due to transmitter characteristics, is corrupted by an unknown frequency offset. The optimum TOA estimator, for the case of no frequency uncertainty, is first presented, together with a lower bound on the variance of the estimate generated. This is followed by the consideration of a suboptimum TOA estimator for which a high signal-to-noise ratio (SNR) performance analysis is carried out; here, the effects of frequency uncertainty are included. Next, the zero-crossing properties of the derivative of the (suboptimum) estimation statistic are presented and the results used to derive an upper bound to the TOA estimate variance that is valid for all SNR values. This latter result is significant because it displays the system threshold effect and complements performance lower bounds that may be derived via other methods. In addition, the method presented here may be applied to other optimum and suboptimum systems where a discrete set of parameters is to be estimated.

Ground mapping resolution accuracy of a scanning radiometer from a geostationary satellite.

Abstract: Measures of the spatial and spatial rate (frequency) mapping of scanned visual imagery from an earth reference system to a spin-scan geostationary satellite are examined. Mapping distortions and coordinate inversions to correct for these distortions are formulated in terms of geometric transformations between earth and satellite frames of reference. Probabilistic methods are used to develop relations for obtainable mapping resolution when coordinate inversions are employed.

A microprocessor selective encryption terminal for privacy protection

Abstract: This paper reports on an experiment performed by the METREK Division of The MITRE Corporation from November 1975 through August 1976. The purpose of the experiment was to determine how effectively a low cost microcomputer could provide privacy protection to a user of a time-shared computer system. The microprocessor was used to selectively encrypt information entered at the terminal before transmission to the host computer so that the protected information never appears in plaintext form at the host computer. The advantages and disadvantages of this approach along with the operational details of the experimental system are presented.

Concerning the logical comparison of atc separation standard assessment models

Abstract: There exist many models for the determination or assessment of safe separation standards between aircraft flying under an air traffic control (ATC) system. Most models fall within the general categories of collision risk or collision avoidance. This paper presents a framework for the qualitative comparison of the logical structure of these several models. Thus the merits and appropriateness of the several models may be more critically evaluated, and better definition of model applicability made.

Data collection system for transit buses

Abstract: A breadboard of an Operational Data Collection System (ODCS) was constructed to collect passenger, revenue, mileage, and identification data from onboard transit buses. The data was stored on standard Phillips magnetic cassettes for later processing. The collection and storage unit (data collector) was assembled with off-the-shelf microprocessor components and some interface circuitry. The software was organized as a group of independent processors that were simulated via the interrupt system of the microprocessor Central Processor Unit. Each processor was associated with one of the physical units of ODCS, such as the registering fare box or the automatic passenger counter, and may be perceived as an extension to the physical unit.

The terminal area automated path generation problem

Abstract: The automated terminal area path generation problem in the advanced Air Traffic Control System (ATC), has been studied. Definitions, input, output and the interrelationships with other ATC functions have been discussed. Alternatives in modeling the problem have been identified. Problem formulations and solution techniques are presented. In particular, the solution of a minimum effort path stretching problem (path generation on a given schedule) has been carried out using the Newton-Raphson trajectory optimization method. Discussions are presented on the effect of different delivery time, aircraft entry position, initial guess on the boundary conditions, etc. Recommendations are made on real-world implementations.