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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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NASA flight test of hingeless rotor compound helicopter to determine lift sharing characteristics, showing rotor lift dependence on airspeed
On-line central data processing system connected to time shared computer for recording data from test facilities, discussing hardware configuration, software considerations and advantages
Multiprogramming subsystem implementation by time sharing computer in tracking station
Power ratios of wanted to unwanted signals for frequency sharing between FM and AM-VSB television transmission systems
Special purpose computer organized as time-shared digital filter for real time applications with adaptable coefficients, programming and multiplexing scheme
Loops and paths in Mason signal flow graph of linear systems using algorithm with remote time shared digital computation
Frequency sharing between satellite-transmitted FM TV signals and terrestrially transmitted AM-VSB TV signals
Time shared computer system providing real time service to multiple laboratory instrumentation, discussing high speed channel, computer control and data abstracting techniques
Integrated time shared instrumentation display for aerospace vehicle simulators
There are numerous examples of cases where the human operator is confronted with several tasks occurring simultaneously and continuously in time. The current study is an investigation into the nature of attention sharing between two continuous tasks with independent input-output modes. Eleven subjects were tested using a zero order compensatory control task with three levels of difficulty (input bandwidth) for each subject. As a secondary task on half of the trials, the subjects were also required to verbally shadow a random auditory input. Results from an extensive time and frequency domain analysis of the data are presented and discussed. The evidence supports a single channel model for continuous dual-task control.
The experimental program was based on the premise that the plastic sizing cycle, which each pressure vessel is subjected to prior to operation, acts as an effective proof test of the liner, screening out all flaws or cracks larger than a critical size. In doing so, flaw growth potential is available for cyclic operation at pressures less than the sizing pressure. Static fracture and cyclic life tests, involving laboratory type specimens and filament overwrapped tanks, were conducted on three liner materials: (1) 2219-T62 aluminum, (2) Inconel X750 STA, and (3) cryoformed 301 stainless steel. Variables included material condition, thickness, flaw size, flaw shape, temperature, sizing stress level, operating stress level and minimum-to-maximum operating stress ratio. From the empirical data base obtained, a procedure was established by which the service life of composite tanks with load sharing liners could be guaranteed with a high degree of confidence.
NASA-Ames Research Center, Stanford University, and Carleton University, Ottawa, Canada, are participating in a joint experiment to evaluate the feasibility and effectiveness of college curriculum sharing using compressed digital television and the Communications Technology Satellite (CTS). Each university will offer televised courses to the other during the 1976-1977 academic year via CTS, a joint program by NASA and the Canadian Department of Communications. The video compression techniques to be demonstrated will enable economical interconnection of educational institutions using existing and planned domestic satellites.
Domestic communication satellites and video compression techniques will increase communication channel capacity and reduce cost of video transmission. NASA Ames Research Center, Stanford University and Carleton University are participants in an experiment to develop, demonstrate, and evaluate college course sharing techniques via satellite using video compression. The universities will exchange televised seminar and lecture courses via CTS. The experiment features real-time video compression with channel coding and quadra-phase modulation for reducing transmission bandwidth and power requirements. Evaluation plans and preliminary results of Carleton surveys on student attitudes to televised teaching are presented. Policy implications for the U.S. and Canada are outlined.
The lack of adequate institutional mechanisms to regulate, monitor and govern the use of commonly owned world resources appears to be politically destabilizing and subject to socioeconomic pressures of overpopulation, food shortages, cartelism, terrorism, and wealth distribution to developing countries. The capacity and propensity to wage war and its potential consequences are elaborated. It is shown that technology is one of the dominant factors affecting the exploration and management of commonly shared resources.
A modular dc power supply power sharing technique was developed for the Apollo telescope mount electrical power sytem on Skylab. The advantages and disadvantages of various techniques used are reviewed and compared. The new technique design is discussed, and results of its implementation in the power system are reviewed.
A nondissipative circuit for automatic load sharing in parallel converter modules having push-pull power transistors is presented. Each transistor has a separate current-sensing transformer and an impedance-adjusting transformer in series with its collector. The impedance-adjusting transformer functions as a current-controlled variable impedance that is responsive to the difference between the peak collector current of the transistor and the average peak current of all collector currents of power transistors in all modules, thereby to control the collector currents of all power transistors with reference to the average peak collector current.
As the data rates required for digitally encoded television are reduced, satellite systems employing the transmission of digitally encoded television will become attractive. It is likely that television transmitted in this format will be adjacent to or in the same frequency band as television transmissions in other modulation formats, so a knowledge of carrier to interference power ratios as a function of assessed picture quality will be required for frequency sharing between these different modulation formats. This paper presents the results of subjective and quantitative tests describing the results of interference to a particular digital television system from a frequency modulated (FM) television system, and for interference to an FM television system from a digital television system.
Time shared systems permit the fixed costs of computing resources to be spread over large numbers of users. However, bottleneck results in the theory of closed queueing networks can be used to show that this economy of scale will be offset by the increased congestion that results as more users are added to the system. If one considers the total costs, including the congestion cost, there is an optimal number of users for a system which equals the saturation value usually used to define system capacity.