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At least 181 records · Page 10

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NASA NTRS1984

Error determination of a successive correction type objective analysis scheme

The Purdue Regional Objective Analysis of the Mesoscale (PROAM) is a successive correction type scheme for the analysis of surface meteorological data. The scheme is subjected to a series of experiments to evaluate its performance under a variety of analysis conditions. The tests include use of a known analytic temperature distribution to quantify error bounds for the scheme. Similar experiments were conducted using actual atmospheric data. Results indicate that the multiple pass technique increases the accuracy of the analysis. Furthermore, the tests suggest appropriate values for the analysis parameters in resolving disturbances for the data set used in this investigation.

Smith, D. R.↗

NASA NTRS1986

Kinetics of successive seeding of monodisperse polystyrene latexes. I - Initiation via potassium persulfate. II - Azo initiators with and without inhibitors

The polymerization kinetics of monodisperse polystyrene latexes with diameters of 1 micron are studied. The monodisperse latexes were prepared by the successive seeding method using 1 mM K2S2O8 with an 8 percent emulsifier surface coverage and 0.5 mM K2S2O8 with a 4 percent emulsifier surface coverage, and the kinetics were measured in a piston/cylinder dialometer. The data reveal that the polymerization rate decreases with increasing particle size; and the surface charge decreases with increasing particle size. The effects of initiators (AIBN and AMBN) and inhibitors (NH24SCN, NaNO2, and hydroquinone) on the product monodispersity and polymerization kinetics of latexes with diameters greater than 1 micron are investigated in a second experiment. It is observed that hydroquinone combined with AMBN are most effective in reducing nucleation without causing flocculation. It is noted that the kinetic transition from emulsion to bulk is complete for a particle size exceeding 1 micron in which the polymerization rate is independent of the particle size.

Sudol, E. D.↗

NASA NTRS1987

On the concept of varying influence radii for a successive corrections objective analysis

This paper discusses objective analysis techniques known as 'methods of successive corrections' which were introduced by Cressman (1959) and developed for the analysis of mesoscale weather systems by Barnes (1964 and 1973). Theoretical filter response characteristics of the Barnes method are compared for filter parameters set to retrieve the short wavelengths and then build in the long wavelengths. The accuracy of the method is judged by the ability of the filters to restore desired wavelengths and remove undesired wavelengths. It was found that no single selection of filter parameters for the two-pass Barnes method gives the best analysis for all wavelengths. A three-pass hybrid method is shown to reduce this problem.

Achtemeier, Gary L.↗

NASA NTRS1988

Successful completion of a cyclic ground test of a mercury ion auxiliary propulsion system

An engineering model Ion Auxiliary Propulsion System (IAPS) 8-cm thruster (S/N 905) has completed a life test at NASA Lewis Research Center. The mercury ion thruster successfully completed and exceeded the test goals of 2557 on/off cycles and 7057 hr of operation at full thrust. The final 1200 cycles and 3600 hr of the life test were conducted using an engineering model of the IAPS power electronics unit (PEU) and breadboard digital controller and interface unit (DCIU). This portion of the test is described in this paper with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were constant throughout the test with only minor variations. The engineering model power electronics unit operated without malfunction; the flight software in the digital controller and interface unit was exercised and verified. Post-test inspection of the thruster revealed facility enhanced accelerator grid erosion but overall the thruster was in good condition. It was concluded that the thruster performance was not drastically degraded by time or cycles. Additional cyclic testing is currently under consideration.

Francisco, David R.↗

NASA NTRS1987

International cooperation in planetary exploration - Past success and future prospects

A review is given of the ways in which the National Aeronautics and Space Administration (NASA) has participated in international efforts to explore the solar system. Past examples of successful international cooperative programs are described. Prospects for future cooperative efforts are discussed with emphasis placed on current events, issues, and trends which are likely to affect possibilities for cooperation over the next 5 to 10 years. Key factors which will play a major role in shaping future prospects for cooperation include the move towards balancing the budget in the United States and the impact of the Challenger accident on the NASA program.

Rosendhal, Jeffrey D.↗

NASA NTRS1988

Successful completion of a cyclic ground test of a mercury Ion Auxiliary Propulsion System

Francisco, David R.↗

NASA NTRS1989

A system management methodology for building successful resource management systems

This paper presents a system management methodology for building successful resource management systems that possess lifecycle effectiveness. This methodology is based on an analysis of the traditional practice of Systems Engineering Management as it applies to the development of resource management systems. The analysis produced fifteen significant findings presented as recommended adaptations to the traditional practice of Systems Engineering Management to accommodate system development when the requirements are incomplete, unquantifiable, ambiguous and dynamic. Ten recommended adaptations to achieve operational effectiveness when requirements are incomplete, unquantifiable or ambiguous are presented and discussed. Five recommended adaptations to achieve system extensibility when requirements are dynamic are also presented and discussed. The authors conclude that the recommended adaptations to the traditional practice of Systems Engineering Management should be implemented for future resource management systems and that the technology exists to build these systems extensibly.

Hornstein, Rhoda Shaller↗

NASA NTRS1990

Success of the Tracking and Data Relay Satellite System (TDRSS)

The paper provides historical data and presents two parameters for evaluating the success of the Tracking and Data Relay Satellite System (TDRSS). The TDRSS provides high rate data from missions such as the Shuttle and Landsats, and lower rate data from missions such as the Solar Mesosphere Explorer and the Earth Radiation Budget Satellite. Two parameters have been established as measurements of the ability of the system to transmit user commands and telemetry data, i.e., availability and proficiency. Availability is the system's readiness to support any and all user requirements 24 hours per day, 7 days per week. Proficiency is the ratio of actual support provided to scheduled support.

Harris, David W.↗

NASA NTRS1990

An 8-b 1.3-MHz successive-approximation A/D converter

A new successive-approximation A/D converter is described. It combines a string of equal-valued polysilicon resistors and a set of ratioed capacitors in a unique circuit configuration so that a high sampling rate is achieved. The comparator is realized by a chopper-stabilized amplifier to reduce the effect of the offset voltages of MOS amplifiers. The converter performs an 8-b monotonic conversion with a differential nonlinearity less than 1 LSB in 770 nsec. The die area is 3750 sq mil. This new conversion technique can also be utilized in a pipelined A/D converter (Temes, 1985) and enables it to achieve high speed.

Hadidi, KH.↗

NASA NTRS1990

Software technology insertion: A study of success factors

Managing software development in large organizations has become increasingly difficult due to increasing technical complexity, stricter government standards, a shortage of experienced software engineers, competitive pressure for improved productivity and quality, the need to co-develop hardware and software together, and the rapid changes in both hardware and software technology. The 'software factory' approach to software development minimizes risks while maximizing productivity and quality through standardization, automation, and training. However, in practice, this approach is relatively inflexible when adopting new software technologies. The methods that a large multi-project software engineering organization can use to increase the likelihood of successful software technology insertion (STI), especially in a standardized engineering environment, are described.

Lydon, Tom↗

NASA NTRS1992

The cosmic radiation in the heliosphere at successive solar minima

Cosmic ray observations at 1 AU are compared for the last three solar minimum periods along with the 1977/1989 and 1987 Pioneer 10 and Voyager 1 and 2 data from the outer heliosphere. There is good agreement between the 1965 and 1987 Galactic cosmic ray H and He spectra at 1 AU. Significant and complex differences are found between the 1977/1978 and 1987 measurements of the Galactic and anomalous cosmic ray components at 1 and 15 AU. In the outer heliosphere there are negative latitudinal gradients that reach their maximum magnitude when the inclination of the outer heliosphere current sheet is at a minimum. The radial gradients decrease with heliocentric distance as about 1/r exp 0.7 and do not differ significantly at the successive solar minima. The measured radial and latitudinal gradients are used to estimate the particle transport parameters in the outer heliosphere. Using the local interstellar He spectrum of Webber et al. (1987), it is estimated that the modulation boundary is of the order of 160 AU.

Mcdonald, Frank B.↗

NASA NTRS1992

Spacelab Life Sciences 1, development towards successive life sciences flights

A general review is presented of flight data and related hardware developments for Spacelab Life Sciences (SLS) 1 with an eye toward applying this knowledge to projected flight planning. Specific attention is given to the Research Animal Holding Facility (RAHF), the General Purpose Work Station (GPWS), the Small Mass Measuring Instrument (SMMI), and the Animal Enclosure Module (AEM). Preflight and in-flight testing methods are detailed including biocompatibility tests, parametric engineering sensitivity analyses, measurements of environmental parameters, and studies of operational interfaces. Particulate containment is demonstrated for some of the equipment, and successful use of the GPWS, RAHF, AEM, and SMMI are reported. The in-flight data are useful for developing more advanced hardware such as the AEM for SLS flight 2 and the modified RAHF for SLS flight 3.

Dalton, B. P.↗

NASA NTRS1992

OAST space research and technology applications: Technology transfer successes

The ultimate measure of success in the Space Research and Technology Program is the incorporation of a technology into an operational mission. Charts are presented that describe technology products which OAST has helped support that (1) have been used in a space mission, (2) have been incorporated into the baseline design of a flight system in the development phase, or (3) have been picked up by a commercial or other non-NASA user. We hope that these examples will demonstrate the value of investment in technology. Pictured on the charts are illustrations of the technology product, the mission or user which has incorporated the technology, and where appropriate, results from the mission itself.

Reck, Gregory M.↗

NASA NTRS1951

Method of successive approximations for the solution of certain problems in aerodynamics

A method of successive approximations for the solution of problems in the fields of diffusion, boundary-layer flow, and heat-transfer is illustrated by solving problems in each of these fields. In most of the examples, the approximate solutions are compared with known accurate solutions and the agreement is shown to be good.

FLOW, TURBULENT - DIFFUSION↗

NASA NTRS1993

Predicting scheduling success

This paper provides an analytical formulation to predict scheduling success for a class of problems frequently referred to as activity scheduling. Space Network communications scheduling is an example of activity scheduling. The principal assumption is that the activity start times are randomly distributed over the available time in the time line. The formulation makes it possible to estimate how much of the demand can be scheduled as a function of the demand, number of resources, activity duration, and activity flexibility. The paper includes computed results for a variety of resource and demand conditions. The results demonstrate that even with highly flexible activities, it is difficult to schedule demand greater than 60 percent of resources without the use of optimization and conflict resolution capabilities in the scheduling system.

Messing, Fredric↗

NASA NTRS1994

Task automation in a successful industrial telerobot

In this paper, we discuss cooperative work by Oak Ridge National Laboratory and Remotec, Inc., to automate components of the operator's workload using Remotec's Andros telerobot, thereby providing an enhanced user interface which can be retrofit to existing fielded units as well as being incorporated into new production units. Remotec's Andros robots are presently used by numerous electric utilities to perform tasks in reactors where substantial exposure to radiation exists, as well as by the armed forces and numerous law enforcement agencies. The automation of task components, as well as the video graphics display of the robot's position in the environment, will enhance all tasks performed by these users, as well as enabling performance in terrain where the robots cannot presently perform due to lack of knowledge about, for instance, the degree of tilt of the robot. Enhanced performance of a successful industrial mobile robot leads to increased safety and efficiency of performance in hazardous environments. The addition of these capabilities will greatly enhance the utility of the robot, as well as its marketability.

Spelt, Philip F.↗

NASA NTRS1995

Successful product realization strategies

Product realization is the process of defining, designing, developing, and delivering products to the market. While the main thrust of this JTEC panel was to conduct a complete investigation of the state of Japanese low-cost electronic packaging technologies, it is very difficult to totally separate the development of technology and products from the product realization process. Japan's electronics firms adhere to a product realization strategy based on a strong customer focus, a consistent commitment to excellence in design, and a cost-effective approach to technology commercialization. The Japanese product-pull strategy has been a successful driver and influencing factor in every aspect of the product development cycle.

Peeples, John↗

NASA NTRS1994

The successful management of programs for human factors certification of advanced aviation technologies

In recent years there have been immense pressures to enact changes on the air traffic control organizations of most states. In addition, many of these states are or have been subject to great political, sociological and economic changes. Consequently, any new schemes must be considered within the context of national or even international changes. Europe has its own special problems, and many of these are particularly pertinent when considering human factors certification programs. Although these problems must also be considered in the wider context of change, it is usually very difficult to identify which forces are pressing in support of human factors aspects and which forces are resisting change. There are a large number of aspects which must be taken into account if human factors certification programs are to be successfully implemented. Certification programs would be new ventures, and like many new ventures it will be essential to ensure that managers have the skills, commitment and experience to manage the programs effectively. However, they must always be aware of the content and the degree of certainty to which the human factors principles can be applied - as Debons and Horne have carefully described. It will be essential to avoid the well known pitfalls which occur in the implementation of performance appraisal schemes. While most appraisal schemes are usually extremely well thought out, they often do not produce good results because they are not implemented properly and staff therefore do not have faith in them. If the manager does not have the commitment and interest in his/her staff as human beings, then the schemes will not be effective. Thus, one aspect of considering human factors certification schemes is within the context of a managed organization. This paper outlines some of the management factors which need to be considered for the air traffic control services. Many of the points received attention during the plenary sessions while others were covered by the working groups when the question arose of how various aspects of human factors certification programs would be managed. Management and organizational issues will certainly need to be included in any frame of reference by those who may be involved in developing certification programs.

Baldwin, Rod↗