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At least 1,279 records · Page 71

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NASA NTRS1979

Adaptive allocation of decisionmaking responsibility between human and computer in multitask situations

As human and computer come to have overlapping decisionmaking abilities, a dynamic or adaptive allocation of responsibilities may be the best mode of human-computer interaction. It is suggested that the computer serve as a backup decisionmaker, accepting responsibility when human workload becomes excessive and relinquishing responsibility when workload becomes acceptable. A queueing theory formulation of multitask decisionmaking is used and a threshold policy for turning the computer on/off is proposed. This policy minimizes event-waiting cost subject to human workload constraints. An experiment was conducted with a balanced design of several subject runs within a computer-aided multitask flight management situation with different task demand levels. It was found that computer aiding enhanced subsystem performance as well as subjective ratings. The queueing model appears to be an adequate representation of the multitask decisionmaking situation, and to be capable of predicting system performance in terms of average waiting time and server occupancy. Server occupancy was further found to correlate highly with the subjective effort ratings.

Chu, Y.-Y.↗

NASA NTRS1981

Determination of crash test pulses and their application to aircraft seat analysis

Deceleration time histories (crash pulses) from a series of twelve light aircraft crash tests conducted at NASA Langley Research Center (LaRC) were analyzed to provide data for seat and airframe design for crashworthiness. Two vertical drop tests at 12.8 m/s (42 ft/s) and 36 G peak deceleration (simulating one of the vertical light aircraft crash pulses) were made using an energy absorbing light aircraft seat prototype. Vertical pelvis acceleration measured in a 50 percentile dummy in the energy absorbing seat were found to be 45% lower than those obtained from the same dummy in a typical light aircraft seat. A hybrid mathematical seat-occupant model was developed using the DYCAST nonlinear finite element computer code and was used to analyze a vertical drop test of the energy absorbing seat. Seat and occupant accelerations predicted by the DYCAST model compared quite favorably with experimental values.

Alfaro-Bou, E.↗

NASA NTRS1981

Technical writing practically unified through industry

General background details in the development of a university level technical writing program, based upon the writing tasks of the student's occupations, are summarized. Objectives and methods for unifying the courses of study with the needs of industry are discussed. Four academic course divisions, Industries Technologies, in which preparation and training are offered are: Animal, Horticulture, Agriculture, and Agricultural Business. Occupational competence is cited as the main goal for these programs in which technical writing is to be practically unified through industry. Course descriptions are also provided.

Houston, L. S.↗

NASA NTRS1980

Analysis of airborne RF measurements from U.S.A. urban areas

The paper presents in-situ, airborne survey radio-frequency measurements, which were made over the 400-1000 MHz range in May 1977 during the ASSESS-II Space Shuttle/Spacelab simulation aircraft flights. Measurements were made from altitudes of 10,000 to 33,000 feet with a downward-directed 70 deg wide, half-power beamwidth receiving antenna pattern. Channel occupancy percentages are given within a 50 MHz spectrum width, and continuous spectrum-scan measurements are presented for selected locations on the USA West Coast, showing the channel occupancy environment within the 806-890 MHz mobile-service band.

Taylor, R. E.↗

NASA NTRS1984

Human response to vibroacoustic environments of space vehicles

To insure efficient utilization of the system, space station design and operations will require special habitability considerations for the occupants and crew because of the relatively long duration missions. Of particular concern is the environment in which the personnel will live and work, and how it affects both the performance and comfort of the occupants. Current criteria do not consider possible effects of reduced gravity, long duration, and confinement. Preliminary to developing space station vibroacoustic habitability criteria, the adequacy of criteria for other space vehicles has been reviewed. In this paper, responses to the noise and vibration environments of both Skylab and Shuttle are discussed. Some astronauts have reported sleep interference, communication interference, distraction, and general annoyance as noise related complaints. In addition, information from the Russian Salyut missions, as well as similar based situtations (e.g., submarines), is reviewed.

Willshire, K. F.↗

NASA NTRS1990

Radiological health risks to astronauts from space activities and medical procedures

Radiation protection standards for space activities differ substantially from those applied to terrestrial working situations. The levels of radiation and subsequent hazards to which space workers are exposed are quite unlike anything found on Earth. The new more highly refined system of risk management involves assessing the risk to each space worker from all sources of radiation (occupational and non-occupational) at the organ level. The risk coefficients were applied to previous space and medical exposures (diagnostic x ray and nuclear medicine procedures) in order to estimate the radiation-induced lifetime cancer incidence and mortality risk. At present, the risk from medical procedures when compared to space activities is 14 times higher for cancer incidence and 13 times higher for cancer mortality; however, this will change as the per capita dose during Space Station Freedom and interplanetary missions increases and more is known about the risks from exposure to high-LET radiation.

Peterson, Leif E.↗

NASA NTRS1990

Runway Exit Designs for Capacity Improvement Demonstrations. Phase 1: Algorithm Development

A description and results are presented of a study to locate and design rapid runway exits under realistic airport conditions. The study developed a PC-based computer simulation-optimization program called REDIM (runway exit design interactive model) to help future airport designers and planners to locate optimal exits under various airport conditions. The model addresses three sets of problems typically arising during runway exit design evaluations. These are the evaluations of existing runway configurations, addition of new rapid runway turnoffs, and the design of new runway facilities. The model is highly interactive and allows a quick estimation of the expected value of runway occupancy time. Aircraft populations and airport environmental conditions are among the multiple inputs to the model to execute a viable runway location and geometric design solution. The results presented suggest that possible reductions on runway occupancy time (ROT) can be achieved with the use of optimally tailored rapid runway designs for a given aircraft population. Reductions of up to 9 to 6 seconds are possible with the implementation of 30 m/sec variable geometry exits.

Trani, A. A.↗

NASA NTRS1992

The Use of Subcarriers in Future DSN Missions

The performance of deep space telemetry signals that employ a residual carrier modulation technique is compared in the presence and absence of a subcarrier. When the subcarrier is present, the performance for the resulting pulse-coded modulation/phase-shift keyed/phase-modulated (PCM/PSK/PM) scheme is evaluated for both sine wave and square wave subcarriers and non-return-to zero (NRZ) data. When the subcarrier is absent, the performance for the resulting PCM/PM technique is evaluated for both the NRZ and the bi-phase data format. The comparison is based on telemetry performance as well as bandwidth efficiency. The first criterion is characterized in terms of the symbol error rate (SER) as a function of symbol SNR, loop bandwidth-to-data rate ratio, and modulation index. The bandwidth efficiency is characterized by the occupancy factor. The results of both the analysis and measurements show that when the interference-to-carrier ratio (ICR) is less than -15 dB, the performance degradation in the absence of a subcarrier is negligible. Various combinations of loop bandwidth-to-data rate ratios and modulation indices that achieve this performance are derived and listed. Bandwidth occupancy comparison indicates that PCM/PM/NRZ is the most efficient in this regard. Therefore, by eliminating the subcarrier and using the PCM/PM/NRZ scheme, many advantages can be realized without any sacrifice in performance.

Shihabi, M. M.↗

NASA NTRS1993

Energy-absorbing-beam design for composite aircraft subfloors

Data have been presented from the design support testing of composite energy absorbing (EA) aircraft subfloor structures. The focus of the current study is the design and testing of subfloor structural concepts that would limit the loads transmitted to occupants to less than 20 g at crush speeds of approximately 30 fps. The EA composite subfloor is being designed to replace an existing noncrashworthy metallic subfloor in a composite aircraft prior to a full-scale crash test. A sandwich spar construction of a sine wave beam was chosen for evaluation and was found to have excellent energy absorbing characteristics. The design objective of obtaining sustained crushing loads of the spar between 200-300 lbf/inch were achieved for potentially limiting occupants loads to around 20 g's. Stroke efficiency of up to 79 percent of the initial spar height under desired sustained crushing loads was obtained which is far greater than the level provided by metal structure. Additionally, a substantial residual spar stiffness was retained after impact, and the flange integrity, which is critical for seat retention, was maintained after crushing of the spars.

Carden, Huey D.↗

NASA NTRS1953

Accelerations and Passenger Harness Loads Measured in Full-Scale Light-Airplane Crashes

Full-scale light-airplane crashes simulating stall-spin accidents were conducted to determine the decelerations to which occupants are exposed and the resulting harness forces encountered in this type of accident. Crashes at impact speeds from 42 to 60 miles per hour were studied. The airplanes used were of the familiar steel-tube, fabric-covered, tandem, two-seat type. In crashes up to an impact speed of 60 miles per hour, crumpling of the forward fuselage structure prevented the maximum deceleration at the rear-seat location from exceeding 26 to 33g. This maximum g value appeared independent of the impact speed. Restraining forces in the seatbelt - shoulder-harness combination reached 5800 pounds. The rear-seat occupant can survive crashes of the type studied at impact speeds up to 60 miles per hour, if body movement is restrained by an adequate seatbelt-shoulder-harness combination so as to prevent injurious contact with obstacles normally present in the cabin. Inwardly collapsing cabin structure, however, is a potential hazard in the higher-speed crashes.

Eiband, A. Martin↗

NASA NTRS1993

Baseline characteristics of different strata of astronaut corps

The Longitudinal Study of Astronaut Health (LSAH) is an epidemiological study designed to study the effects of the occupational exposures incurred by astronauts in health outcomes and changes in physiological variables. Between 1959 and 1991, 195 individuals were selected for the program. The medical standards for selection have remained essentially unchanged since the Mercury Program, but the range and stringency of these criteria have been modified. Demographic and physiological variables identified during the selection year are examined for various strata of the Astronaut Corps. Specifically, age, sex, race, education, usual occupation, military affiliation, medical history, family medical history, visual and hearing measurements, physical exam variables, and specific laboratory values are investigated. Differences are examined in astronauts for the following criteria: (1) were selected prior to 1970 (n = 73) versus those selected after 1970 (n = 122); (2) have flown multiple missions versus those who have flown less than two missions; (3) have walked in space versus all others; (4) have more than 500 hours of mission time versus all others; and (5) have gone to the Moon versus all others. Length of time served in the Astronaut Corps is examined for each of these strata.

Hamm, Peggy B.↗

NASA NTRS1993

Efficient management of cardiovascular risk screening programs

The Environmental Health Unit, located on-site at the the Goddard Space Flight Center (GSFC), is responsible for the implementation of the Center's Employee Environmental and Occupational Health Program. The Health Unit, Health Physics (HP), and Industrial Hygiene (IH) staffs collaborate to provide quality service to the employees at GSFC. The Health Unit staff identifies, evaluates, and ensures the control of occupational hazards on the Center. In the past, components of the Industrial Hygiene Program have included the Industrial Hygiene Health Hazard Identification Program (IHHIP), the Hearing Conservation Program (HCP), the Hazard Communication Program, and the bi-annual fume hood survey. More recently, the Environmental Health Unit has expanded its services by adding the Ergonomics Program. Various aspects of the Ergonomics Program are discussed.

Roth, Carol↗

NASA NTRS1993

Bloodborne Pathogens Program

The final rule on the Occupational Exposure to Bloodborne Pathogens was published in the Federal Register on Dec. 6, 1991. This Standard, 29 CFR Part 1910.130, is expected to prevent 8,900 hepatitis B infections and nearly 200 deaths a year in healthcare workers in the U.S. The Occupational Medicine and Environmental Health Services at KSC has been planning to implement this standard for several years. Various aspects of this standard and its Bloodborne Pathogens Program at KSC are discussed.

Blasdell, Sharon↗

NASA NTRS1993

OSHA Bloodborne Pathogens Standards Exposure Control Plan

The Hummer Associates Exposure Control Plan is designed to reduce significant occupational exposure to bloodborne pathogens and infectious materials for Hummer Associates health care personnel. Under universal precautions, all patients and all body fluids are considered potentially infectious for bloodborne pathogens. Medical personnel need not be at increased risk if universal precautions are correctly understood and followed. This program covers all employees who could reasonably anticipate contact with blood or other potentially infectious materials during the performance of their job responsibilities. Although HIV and hepatitis B are mentioned most often, this program applies to all bloodborne diseases. The two main components needed to implement this program are universal precautions and engineering/work practice controls. This program covers all employees who may have occupational exposure to blood or other potentially infectious materials. Other aspects of this program are discussed.

Luhrs, Caro Elise↗

NASA NTRS1994

Development of microgravity, full body functional reach envelope using 3-D computer graphic models and virtual reality technology

In microgravity conditions mobility is greatly enhanced and body stability is difficult to achieve. Because of these difficulties, optimum placement and accessibility of objects and controls can be critical to required tasks on board shuttle flights or on the proposed space station. Anthropometric measurement of the maximum reach of occupants of a microgravity environment provide knowledge about maximum functional placement for tasking situations. Calculations for a full body, functional reach envelope for microgravity environments are imperative. To this end, three dimensional computer modeled human figures, providing a method of anthropometric measurement, were used to locate the data points that define the full body, functional reach envelope. Virtual reality technology was utilized to enable an occupant of the microgravity environment to experience movement within the reach envelope while immersed in a simulated microgravity environment.

Lindsey, Patricia F.↗

NASA NTRS1994

Aerospace Industries Association (AIA) work practices report for composites

In an effort to gain a better understanding of effective safety and health work practice controls for composite manufacturing operations, the Aerospace Industries Association (AIA) Occupational Safety and Health Committee established a Composites Task Group. The group's task was to provide AIA members with recommendations for minimizing occupational exposure risk and to determine research needs and information gaps. The strategy included a review of toxicological information on composites, a review of member company experience and control methods, and interaction with other professional organizations who share an interest in composite work practices.

Luca, Jackie↗

NASA NTRS1994

Skin exposure: Assessing the hazard in the workplace

An outline of the Occupational Safety and Health Agency's concerns of skin exposure to hazardous chemicals is presented, followed by the corresponding slide narrations. Specifically, dermatitis and skin absorption as compared to lung absorption are addressed. Lung versus skin exposure is examined for glycol ethers and acrylamide. Examples of skin exposure include PBC's in transformers, toluene and xylene from autobody work, polynuclear aromatics (PNA's) among Coke oven workers, toluene diisocyanate (TDI), and occupational chemical exposures in an academic medical center. Permeation through gloves in the semiconductor industry is addressed as evidence for the need to assess the effectiveness of PPE (Personal Protective Equipment). This leads to the revisions of the PPE standard and the Safety and Health Program standard.

Cummins, Kevin↗

NASA NTRS1994

Size estimation of complexes consisting of hairpin DNAs bound to an assembler-strand

In connection with a model of a primitive translation based entirely on nucleic acids the structural requirements and interactions of small nucleic acids were studied. As shown previously hairpins bind to a complementary single-strand by base pairs of their loop nucleotides if the loop contains at least five nucleotides (Baumann et al 1987). Here, the question is approached to which degree a single-strand, the assembler-strand, is occupied with hairpin molecules. A gapless occupation would allow the close proximity necessary for the assumed peptide bond formation by hairpins bearing an amino acid at their 3'-end. Oligo(dC)(sub n), n = 12, 15, 18, and the investigated hairpins form complexes which are detectable under nondenaturing electrophoretic conditions. The size range is estimated to be 3-4 hairpin molecules to one assembler molecule when oligo(dC)(sub n), n = 15, 18, is used. Due to the limitation of the method, dependence of the migration velocity on the shape which is unique and thus limits the use of marker nucleic acids, and due to the uncertainty if the ends of the assembler form base pairs, a gapless occupation of the assembler is conceivable but not proven.

Baumann, Ulrich↗