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At least 145 records · Page 8

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NASA NTRS1976

SSL: A software specification language

SSL (Software Specification Language) is a new formalism for the definition of specifications for software systems. The language provides a linear format for the representation of the information normally displayed in a two-dimensional module inter-dependency diagram. In comparing SSL to FORTRAN or ALGOL, it is found to be largely complementary to the algorithmic (procedural) languages. SSL is capable of representing explicitly module interconnections and global data flow, information which is deeply imbedded in the algorithmic languages. On the other hand, SSL is not designed to depict the control flow within modules. The SSL level of software design explicitly depicts intermodule data flow as a functional specification.

Austin, S. L.↗

NASA NTRS1977

Specific cooling capacity of liquid nitrogen

The assumed cooling process and the method used to calculate the specific cooling capacity of liquid nitrogen are described, and the simple equation fitted to the calculated specific cooling capacity data, together with the graphical form calculated values of the specific cooling capacity of nitrogen for stagnation temperatures from saturation to 350 K and stagnation pressures from 1 to 10 atmospheres, are given.

Kilgore, R. A.↗

NASA NTRS1977

NASA software specification and evaluation system: Software verification/validation techniques

NASA software requirement specifications were used in the development of a system for validating and verifying computer programs. The software specification and evaluation system (SSES) provides for the effective and efficient specification, implementation, and testing of computer software programs. The system as implemented will produce structured FORTRAN or ANSI FORTRAN programs, but the principles upon which SSES is designed allow it to be easily adapted to other high order languages.

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NASA NTRS1976

Atmospheric, Magnetospheric and Plasmas in Space (AMPS) spacelab payload definition study; volume 4: Part 2, Labcraft payload general specification

The Labcraft Payload General Specification (LPGS) amplifies those general requirements in the Labcraft Program Specification (LPS) to ensure that all hardware, software, and STS elements will successfully function as an integrated system to accomplish the objectives of the first Labcraft mission. Contract End Item Specifications (CEIS) and Procurement Drawings (PDs) prepared and implemented for all deliverable hardware and software elements are discussed.

Keeley, J. T.↗

NASA NTRS1977

Development of standardized specifications for silicon solar cells

A space silicon solar cell assembly (cell and coverglass) specification aimed at standardizing the diverse requirements of current cell or assembly specifications was developed. This specification was designed to minimize both the procurement and manufacturing costs for space qualified silicon solar cell assembilies. In addition, an impact analysis estimating the technological and economic effects of employing a standardized space silicon solar cell assembly was performed.

Scott-Monck, J. A.↗

NASA NTRS1979

Analytical evaluation of the impact of broad specification fuels on high bypass turbofan engine combustors

Six conceptual combustor designs for the CF6-50 high bypass turbofan engine and six conceptual combustor designs for the NASA/GE E3 high bypass turbofan engine were analyzed to provide an assessment of the major problems anticipated in using broad specification fuels in these aircraft engine combustion systems. Each of the conceptual combustor designs, which are representative of both state-of-the-art and advanced state-of-the-art combustion systems, was analyzed to estimate combustor performance, durability, and pollutant emissions when using commercial Jet A aviation fuel and when using experimental referee board specification fuel. Results indicate that lean burning, low emissions double annular combustor concepts can accommodate a wide range of fuel properties without a serious deterioration of performance or durability. However, rich burning, single annular concepts would be less tolerant to a relaxation of fuel properties. As the fuel specifications are relaxed, autoignition delay time becomes much smaller which presents a serious design and development problem for premixing-prevaporizing combustion system concepts.

Taylor, J. R.↗

NASA NTRS1979

Mission analysis and performance specification studies report, appendix A

The Near Term Hybrid Passenger Vehicle Development Program tasks included defining missions, developing distributions of daily travel and composite driving cycles for these missions, providing information necessary to estimate the potential replacement of the existing fleet by hybrids, and estimating acceleration/gradeability performance requirements for safe operation. The data was then utilized to develop mission specifications, define reference vehicles, develop hybrid vehicle performance specifications, and make fuel consumption estimates for the vehicles. The major assumptions which underlie the approach taken to the mission analysis and development of performance specifications are the following: the daily operating range of a hybrid vehicle should not be limited by the stored energy capacity and the performance of such a vehicle should not be strongly dependent on the battery state of charge.

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NASA NTRS1980

NASA/General Electric broad-specification fuels combustion technology program, phase 1

The use of broad specification fuels in aircraft turbine engine combustion systems was examined. Three different combustor design concepts were evaluated for their ability to use broad specification fuels while meeting several specific emissions, performance, and durability goals. These combustor concepts covered a range from those having limited complexity and relatively low technical risk to those having high potential for achieving all of the program goals at the expense of increased technical risk.

Dodds, W. J.↗

NASA NTRS1980

Measurement of the specific refractivities of CF4 and C2F6

In order to relate the measured fringe shift of an interferometer to the density of a medium, the relation between density and refractive index, which is expressed by the specific refractivity, must be known. In the present paper, the specific refractivities of the wind tunnel test gases CF4 and C2F6 are determined in order to verify estimations based on the atomic refractivities of carbon and fluorine. A Twyman-Green two-beam interferometer with a 633-nm He-Ne laser light source was used to measure the specific refractivity as a function of fringe shift as the density of the gas was changed. Values of 0.122 and 0.131 cu cm/g were obtained for CF4 and C2F6 respectively at a temperature of 300 K, which are within 1% of the values computed from the atomic refractivities.

Burner, A. W.↗

NASA NTRS1980

ERSYS-SPP access method subsystem design specification

The STARAN special purpose processor (SPP) is a machine allowing the same operation to be performed on up to 512 different data elements simultaneously. In the ERSYS system, it is to be attached to a 4341 plug compatible machine (PCM) to do certain existing algorithms and, at a later date, to perform other to be specified algorithms. That part of the interface between the 4341 PCM and the SPP located in the 4341 PCM is known as the SPP access method (SPPAM). Access to the SPPAM will be obtained by use of the NQUEUE and DQUEUE commands. The subsystem design specification is to incorporate all applicable design considerations from the ERSYS system design specification and the Level B requirements documents relating to the SPPAM. It is intended as a basis for the preliminary design review and will expand into the subsystem detailed design specification.

Weise, R. C.↗

NASA NTRS1982

NASA Broad Specification Fuels Combustion Technology program - Pratt and Whitney Aircraft Phase I results and status

In connection with increases in the cost of fuels and the reduced availability of high quality petroleum crude, a modification of fuel specifications has been considered to allow acceptance of poorer quality fuels. To obtain the information upon which a selection of appropriate fuels for aircraft can be based, the Broad Specification Fuels Combustion Technology program was formulated by NASA. A description is presented of program-related investigations conducted by an American aerospace company. The specific objective of Phase I of this program has been to evaluate the impact of the use of broadened properties fuels on combustor design through comprehensive combustor rig testing. Attention is given to combustor concepts, experimental evaluation, results obtained with single stage combustors, the stage combustor concept, and the capability of a variable geometry combustor.

Lohmann, R. P.↗

NASA NTRS1982

Formal specification and mechanical verification of SIFT - A fault-tolerant flight control system

The paper describes the methodology being employed to demonstrate rigorously that the SIFT (software-implemented fault-tolerant) computer meets its requirements. The methodology uses a hierarchy of design specifications, expressed in the mathematical domain of multisorted first-order predicate calculus. The most abstract of these, from which almost all details of mechanization have been removed, represents the requirements on the system for reliability and intended functionality. Successive specifications in the hierarchy add design and implementation detail until the PASCAL programs implementing the SIFT executive are reached. A formal proof that a SIFT system in a 'safe' state operates correctly despite the presence of arbitrary faults has been completed all the way from the most abstract specifications to the PASCAL program.

Melliar-Smith, P. M.↗

NASA NTRS1982

Material characterization and specification development for 350 F curing epoxy-graphite materials

New analytical techniques and a processability laminate have been used in the development of a material specification for 350 F curing epoxy-graphite materials. The development of the specification required the evaluation of prepregs which had variations in their processing behavior that were detected only in production. Chemical techniques were used to analyze the prepregs and establish limits on the concentrations of the various chemical constituents. A batch acceptance test laminate was designed to determine suitability of prepregs for production useage. The new specification requires that the processability laminate be ultrasonically and micrographically inspected for voids and porosity. Incorporation of these and other requirements will help to insure material consistency and processability.

Rogers, A. K.↗

NASA NTRS1984

IGES, a key interface specification for CAD/CAM systems integration

The Initial Graphics Exchange Specification (IGES) program has focused the efforts of 52 companies on the development and documentation of a means of graphics data base exchange among present day CAD/CAM systems. The project's brief history has seen the evolution of the Specification into preliminary industrial usage marked by public demonstrations of vendor capability, mandatory requests in procurement actions, and a formalization into an American National Standard in September 1981. Recent events have demonstrated intersystem data exchange among seven vendor systems with a total of 30 vendors committing to offer IGES capability. A full range of documentation supports the IGES project and the recently approved IGES Version 2.0 of the Specification.

Smith, B. M.↗

NASA NTRS1984

Site-Specific Research Conducted in Support of the Salton Sea Solar Pond Project - FY 1982 Report

The design and operation of a salt-gradient solar pond power plant at the Salton Sea presents problems not encountered at small research ponds that were built in the United States. The specific characteristics of the Salton Sea site and the desire to construct the pond using the local clay as a sealant represent major deviations from previous solar pond experience. The site-specific research in support of the plant design is described. The research activity included validation of the spectrophotometric light transmission measurement technique, a search for options for clarifying the turbid and colored water of the Salton Sea, development of water clarification specifications in terms common to industry practice, quantification of gas production from microbiological reactions in the ground, a determination of the combined effects of temperature and salinity on the permeation of the local clays, and a preliminary evaluation of material corrosion.

French, R. L.↗

NASA NTRS1985

Gateway design specification for fiber optic local area networks

This is a Design Specification for a gateway to interconnect fiber optic local area networks (LAN's). The internetworking protocols for a gateway device that will interconnect multiple local area networks are defined. This specification serves as input for preparation of detailed design specifications for the hardware and software of a gateway device. General characteristics to be incorporated in the gateway such as node address mapping, packet fragmentation, and gateway routing features are described.

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NASA NTRS1984

An approach to developing specification measures

An approach to developing specification measures is described. A key feature of the approach is the introduction of a new requirements representation, the Composite Specification Model (CSM). Results are reported from an experiment in which the requirements for a real system are recast using the CSM. Specification measures are then extracted from the CSM representation of the system.

Agresti, W. W.↗

NASA NTRS1984

Investigation of specification measures for the Software Engineering Laboratory (SEL)

Requirements specification measures are investigated for potential application in the Software Engineering Laboratory. Eighty-seven candidate measures are defined; sixteen are recommended for use. Most measures are derived from a new representation, the Composite Specification Model, which is introduced. The results of extracting the specification measures from the requirements of a real system are described.

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