Taxonomy of Human Wayfinding Tasks: A Knowledge-Based Approach

Abstract

Although the term “Wayfinding” has been defined by several authors, it subsumes a whole set of tasks that involve different cognitive processes, drawing on different cognitive components. Research on wayfinding has been conducted with different paradigms using a variety of wayfinding tasks. This makes it difficult to compare the results and implications of many studies. A systematic classification is needed in order to determine and investigate the cognitive processes and structural components of how humans solve wayfinding problems. Current classifications of wayfinding distinguish tasks on a rather coarse level or do not take the navigator's knowledge, a key factor in wayfinding, into account. We present an extended taxonomy of wayfinding that distinguishes tasks by external constraints as well as by the level of spatial knowledge that is available to the navigator. The taxonomy will help to decrease ambiguity of wayfinding tasks and it will facilitate understanding of the differentiated demands a navigator faces when solving wayfinding problems.     

Gaseous cavity at the base of an underwater projectile

The problem of the behavior of the gaseous cavity which is formed at the base of an underwater launched projectile is treated using different approaches. Asymptotic analysis is used to yield expressions for similarity parameters and a simplified hydrodynamic model of the initial stretching phase. A laboratory facility is described, in which launches can be simulated and analyzed by means of pressure measurements and high speed visualizations. Complete calculations are also performed using a numerical “Volume of Fluid” model solving the unsteady Navier-Stokes equations. Results from the three approaches are presented and compared during the cavity stretching phase. Finally, the thermodynamic aspects of the problem are examined.     

An Engineering Approach to Software Configuration Management

Increasingly, digital computers are being incorporated as major hard-ware subsystems in today's large support and operational systems. As a result, computer programs and complex operational procedures, software, are also becoming major system elements. Contrary to much current practice, software must be managed, engineered, and controlled in the same manner as hardware if past pitfalls are to be avoided. NASA's NPC 500-1 and the USAF 375 series establish a basis for an effective hardware/software systems development methodology that must be adopted by both hardware and software engineers and managers.     

The Impact of Integrated Electronics on Aerospace Avionic Subsystems

Integrated electronics or microelectronics is one of today's major technical frontiers. Possibilities offered to the designer of avionics subsystems, for aerospace vehicles, by these techniques, are almost limitless, from the point of view of performance capabilities as well as reliability and maintainability. Application will change current engineering practices in avionics design. Some changes will be easy; in others, problems will appear. This paper discusses these changes, indicating potential gains to be expected as well as potential problem areas. The rise in the application of integrated electronics is expected to be high for the next 10 to 15 years. By 1980, integrated circuitry will have largely replaced the use of discrete components, and the rate-of-increase-of-application curves will level off.     

Measurement of Pressures and Heat Transfer by FM Telemetry

A measurement system for obtaining pressure and heat-transfer data from models flying freely in hypersonic tunnel streams is described. Test models are either released from suspension threads or launched by low-velocity pneumatic launchers and have internal miniaturized frequency-modulated telemetry units. This technique permits the historically desired measurement of support-free afterbody pressure and heat-transfer rates. Base heating and pressure measurements for a cone and a sphere in free flight are included to illustrate application.     

Reanalysis of radiation belt electron phase space density using various boundary conditions and loss models

Data assimilation is becoming an increasingly important tool for understanding the near Earth hazardous radiation environments. Reanalysis of the radiation belts can be used to identify the electron acceleration mechanism and distinguish local acceleration from radial diffusion. However, for any practical applications we need to determine how reliable is reanalysis, and how significant is the dependence of the results on the assumptions of the code and choice of boundary conditions. We present the sensitivity of reanalysis of the radiation belt electron phase space density (PSD) to the assumed location of the outer boundary, using the VERB code and a Kalman filter. We analyze the sensitivity of reanalysis to changes in the electron-loss throughout the domain, and the sensitivity to the assumed boundary condition and its effect on the innovation vector. All the simulations presented in this study for all assumed loss models and boundary conditions, show that peaks in the phase space density of relativistic electrons build up between 4.5 and 6 R_E during relativistic electron flux enhancements in the outer radiation belt. This clearly shows that peaks build up in the heart of the electron radiation belt independent of the assumptions in the model, and that local acceleration is operating there. The work here is also an important step toward performing reanalysis using observations from current and future missions.     

Open systems architecture for integrated RF electronics

The Integrated Sensor System (ISS) program is defining an Open System Architecture (OSA) for Radio Frequency (RF) electronics, which represent the largest portion of an advanced aircraft's avionics flyaway cost. An integrated architecture is used to reduce costs in a number of ways, including time-sharing, centralization of resources, and reduction of the number of unique module types. The OSA approach extends these cost reductions by simplifying technology insertion, using well-understood standards, and increasing use of commercial hardware and software. This paper describes interim results. The work was funded by the Open Systems Joint Task Force (OS-JTF)     

Source and loss processes in the inner magnetosphere

Space Science Reviews -     

Single ion actions: the induction of micronuclei in V79 cells exposed to individual protons.

Understanding the effects of single-particles from conventional radiation biology experiments is problematic due to the stochastics of particle tracks. This complicates the determinations of risk associated with low doses. We have developed a charged particle microbeam, which allows individually counted particles to be delivered to precise cellular locations. The system is capable of delivering a single charged particle with > 99% efficiency. Of these particles 90% are delivered with a resolution of +/- 2 micrometers and 96% with a resolution of +/- 5 micrometers. We have carried out preliminary studies in Chinese hamster V79 cells to monitor the effectiveness of low energy protons at inducing cytological damage. We have used the micronucleus assay as a measure of predominantly lethal chromosome damage. The effects of a single 3.2 MeV proton delivered individually to cells could be measured, with less than 2% of the exposed cells producing micronuclei 24 hours later. The yield of micronuclei formation was essentially linear up to the highest dose (30 particles per cell nucleus) delivered. Ultimately, the ability to target particles to different parts of the cell nucleus may start to impact on models available for chromosome aberration formation and chromosomal Organisation and mechanisms underlying genomic instability.