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At least 19 records
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NASA NTRS2005

Apex Reference Manual 3.0 Beta

Apex is a toolkit for constructing software that behaves intelligently and responsively in demanding task environments. Reflecting its origin at NASA where Apex continues to be developed, current applications include: a) Providing autonomous mission management and tactical control capabilities for unmanned aerial vehicles including an autonomous surveillance helicopter and a simulation prototype of an unmanned fixed-wing aircraft to be used for wildfire mapping; b) Simulating human air traffic controllers, pilots and astronauts to help predict how people might respond to changes in equipment or procedures; and c) Predicting the precise duration and sequence of routine human behaviors based on a human-computer interaction engineering technique called CPM-GOMS. Among Apex s components are a set of implemented reasoning services, such as those for reactive planning and temporal pattern recognition; a software architecture that embeds and integrates these services and allows additional reasoning elements to be added as extensions; a formal language for specifying agent knowledge; a simulation environment to facilitate prototyping and analysis; and Sherpa, a set of tools for visualizing autonomy logic and runtime behavior. In combination, these are meant to provide a flexible and usable framework for creating, testing, and deploying intelligent agent software. Overall, our goal in developing Apex is to lower economic barriers to developing intelligent software agents. New ideas about how to extend or modify the system are evaluated in terms of their impact in reducing the time, expertise, and inventiveness required to build and maintain applications. For example, potential enhancements to the AI reasoning capabilities in the system are reviewed not only for usefulness and distinctiveness, but also for their impact on the readability and general usability of Apex s behavior representation language (PDL) and on the transparency of resulting behavior. A second central part of our approach is to iteratively refine Apex based on lessons learned from as diverse a set of applications as possible. Many applications have been developed by users outside the core development team including engineers, researchers, and students. Usability is thus a central concern for every aspect of Apex visible to a user, including PDL, Sherpa, the Apex installation process, APIs, and user documentation. Apex users vary in their areas of expertise and in their familiarity with autonomy technology. Focusing on usability, a development philosophy summarized by the project motto "Usable Autonomy," has been important part of enabling diverse users to employ Apex successfully and to provide feedback needed to guide iterative, user-centered refinement.

Freed, Michael A.↗
NASA NTRS1999

Compositional Analysis of Martian Soil: Synergism of APEX and MECA Experiments on MPS 2001

The APEX (ATHENA Precursor Experiment) payload for the Mars 2001 mission will analyze soil and dust with a multispectral panoramic imager and an emission spectrometer on a mast on the lander, a Moessbauer spectrometer on the lander robotic arm (RA), and APXS measurements on the Marie Curie rover. These analytical methods will provide data on elemental abundances and mineralogy. The MECA payload on the lander will apply microscopy, AFM, wet chemistry, adhesive substrates, and electrometry to determine the shape and size of particles in the soil and dust, the presence of toxic substances, and electrostatic, magnetic, and hardness qualities of particles. The two experiments will complement one another through several interactions: (1) The panoramic imager provides the geological setting in which both APEX and MECA samples are acquired, (2) The RA provides samples to MECA from the surface and subsurface and will permit APEX analytical tools access to materials below the inunediate surface, (3) Comparisons can be made between elemental analyses of the Moessbauer, IR, APXS on APEX and the wet chemistry of MECA which will define trace elements (ionic species in solution) and soil redox potential and conductivity. (4) APEX bulk compositional measurements will place MECA trace measurements in context, and similarly, MECA microscopy will provide particle size data that may correlate with compositional differences determined by the APEX instruments. Additionally, lithic fragments viewed by the NMCA microscope station should correlate with mineral/rock species inferred by APEX data, (5) If APEX instruments detect quartz for example, the scratch plates of the N4ECA microscope stage will define if a mineral of this hardness is registered during abrasion tests. This is by no means an exhaustive list of potential interactions, but it is clear that both the sheer number of analytical techniques and their complementarity should provide an analytically powerful capability for both planetary and BEDS communities.

Arvidson, R.↗
NASA NTRS1999

Compositional Analysis of Martian Soil: Synergism of APEX and MECA Experiments on MPS 2001

The APEX (ATHENA Precursor Experiment) payload for the Mars 2001 mission will analyze soil and dust with a multispectral panoramic imager and an emission spectrometer on a mast on the lander, a Moessbauer spectrometer on the lander robotic arm (RA), and APXS measurements on the Marie Curie rover. These analytical methods will provide data on elemental abundances and mineralogy. The MECA payload on the lander will apply microscopy, AFM, wet chemistry, adhesive substrates, and electrometry to determine the shape and size of particles in the soil and dust, the presence of toxic substances, and electrostatic, magnetic, and hardness qualities of particles. The two experiments will complement one another through several interactions: (1) The panoramic imager provides the geological setting in which both APEX and MECA samples are acquired, (2) The RA provides samples to MECA from the surface and subsurface and will permit APEX analytical tools access to materials below the immediate surface, (3) Comparisons can be made between elemental analyses of the Moessbauer, IR, APXS on APEX and the wet chemistry of MECA which will define trace elements (ionic species in solution) and soil redox potential and conductivity. (4) APEX bulk compositional measurements will place MECA trace measurements in context, and similarly, MECA microscopy will provide particle size data that may correlate with compositional differences determined by the APEX instruments. Additionally, lithic fragments viewed by the MECA microscope station should correlate with mineral/rock species inferred by APEX data, (5) If APEX instruments detect quartz for example, the scratch plates of the MECA microscope stage will define if a mineral of this hardness is registered during abrasion tests. This is by no means an exhaustive list of potential interactions, but it is clear that both the sheer number of analytical techniques and their complementarity should provide an analytically powerful capability for both planetary and HEDS communities.

Arvidson, R.↗
DOE OSTI2024

Immunization of cows with HIV envelope trimers generates broadly neutralizing antibodies to the V2-apex from the ultralong CDRH3 repertoire

The generation of broadly neutralizing antibodies (bnAbs) to conserved epitopes on HIV Envelope (Env) is one of the cornerstones of HIV vaccine research. The animal models commonly used for HIV do not reliably produce a potent broadly neutralizing serum antibody response, with the exception of cows. Cows have previously produced a CD4 binding site response by homologous prime and boosting with a native-like Env trimer. In small animal models, other engineered immunogens were shown to focus antibody responses to the bnAb V2-apex region of Env. Here, we immunized two groups of cows (n = 4) with two regimens of V2-apex focusing Env immunogens to investigate whether antibody responses could be generated to the V2-apex on Env. Group 1 was immunized with chimpanzee simian immunodeficiency virus (SIV)-Env trimer that shares its V2-apex with HIV, followed by immunization with C108, a V2-apex focusing immunogen, and finally boosted with a cross-clade native-like trimer cocktail. Group 2 was immunized with HIV C108 Env trimer followed by the same HIV trimer cocktail as Group 1. Longitudinal serum analysis showed that one cow in each group developed serum neutralizing antibody responses to the V2-apex. Eight and 11 bnAbs were isolated from Group 1 and Group 2 cows, respectively, and showed moderate breadth and potency. Potent and broad responses in this study developed much later than previous cow immunizations that elicited CD4bs bnAbs responses and required several different immunogens. All isolated bnAbs were derived from the ultralong CDRH3 repertoire. The finding that cow antibodies can target more than one broadly neutralizing epitope on the HIV surface reveals the generality of elongated structures for the recognition of highly glycosylated proteins. The exclusive isolation of ultralong CDRH3 bnAbs, despite only comprising a small percent of the cow repertoire, suggests these antibodies outcompete the long and short CDRH3 antibodies during the bnAb response.

Microbiology↗
NASA NTRS1986

Basic studies on delta wing flow modifications by means of apex fences

The effectiveness of apex fences on a 60-deg delta wing at low speeds was experimentally investigated. Resembling highly swept spoilers in appearance, the fences are designed to fold out of the wing apex region upper surface near the leading edges, where they generate a powerful vortex pair. The intense suction of the fence vortices augments lift in the apex region, the resulting positive pitching moment being utilized to trim trailing edge flaps for lift augmentation during approach and landing at relatively low angles of attack. The fences reduce the apex lift at high angles of attack, leading to a desirable nose-down moment. The above projected functions of the apex fence device were validated and quantified through low speed tunnel tests, comprising upper surface pressure surveys on a semispan model and balance measurements on a geometrically similar fully span wing/body configuration. Fence parameters such as area, shape, hinge position and deflection angle were investigated. Typical results are presented indicating the apex fence potential in controlling the longitudinal characteristics of a tail-less delta.

Hoffler, K. D.↗
NASA NTRS1984

Force and moment measurements on a 74 deg delta wing with an apex flap

Results are presented of a subsonic experimental investigation of an apex flap concept on a 74 deg swept delta wing with trailing-edge flaps. The apex flap comprised approximately 6 percent of the wing area forward of a transverse hinge, allowing for upward and downward deflection angles from +40 deg to -20 deg. Upward deflection forces leading-edge vortex formation on the apex flap, resulting in an increased lift component on the apex area. The associated nose-up moment balances the nose-down moment due to trailing-edge flaps, resulting in sizeable increase in the trimmed lift coefficient particularly at low angles of attack. Nose-down apex deflection may be used to augment the pitch control for rapid recovery from high-alpha maneuvers. This report presents the balance data without analysis.

Buter, T. A.↗
NASA NTRS1991

Early Archean (approximately 3.4 Ga) prokaryotic filaments from cherts of the apex basalt, Western Australia: The oldest cellularly preserved microfossils now known

In comparison with that known from later geologic time, the Archean fossil record is miniscule: although literally hundreds of Proterozoic formations, containing more that 2800 occurrences of bona fide microfossils are now known, fewer than 30 units containing some 43 categories of putative microfossils (the vast majority of which are of questionable authenticity) have been reported from the Archean. Among the oldest known fossils are Early Archean filaments reported from cherts of the Towers Formation and the Apex Basalt of the 3.3-3.6 Ga-old Warrawoona Group of Western Australia. The paleobiologic significance of the Towers Formation microstructures is open to question: thin aggregated filaments are properly regarded as dubiomicrofossils (perhaps biogenic, but perhaps not); therefore, they cannot be regarded as firm evidence of Archean life. Although authentic, filamentous microfossiles were reported from a second Towers Formation locality, because the precise layer containing the fossiliferous cherts was not relocated, this discovery can neither be reconfirmed by the original collector nor confirmed independently by other investigators. Discovery of microfossils in bedded cherts of the Apex Basalt, the stratigraphic unit immediately overlying the Towers Formation, obviates the difficulties stored above. The cellularly preserved filaments of the Apex Basalt meet all of the criteria required of a bona fide Archean microfossils. Recent studies indicate that the Apex assemblage includes at least six morphotypes of uniseriate filaments, composed of barrel-shaped, discoidal, or quadrate cells and exhibiting rounded or conical terminal cells and medial bifurcated and paired half-cells that reflect the occurrence of prokaryotic binary cell division. Interestingly, the majority of these morphotypes are morphologically more similar to extant cyanobacteria than to modern filamentous bacteria. Prokaryotes seem clearly to have been hypobradytelic, and the evidence suggests (but does not prove) that physiologically advanced oxygen-producing photosynthesizers may have been represented in the Early Archean biota.

Schopf, J. W.↗
NASA NTRS2003

Determining the Biogenicity of Microfossils in the Apex Chert, Western Australia, Using Transmission Electron Microscopy

For over a decade, the oldest evidence for life on this planet has been microfossils in the 3.5 Ga Apex Chert in Western Australia. Recently, the biogenicity of these carbon-rich structures has been called into question through reanalysis of the local geology and reinterpretation of the original thin sections. Although initially described as a stratiform, bedded chert of siliceous clasts, the unit is now thought to be a brecciated hydrothermal vein chert. The high temperatures of a hydrothermal environment would probably have detrimental effects to early non-hyperthermophilic life, compared to that of a shallow sea. Conversely, a hydrothermal origin would suggest that if the microfossils were valid, they might have been hyperthermophilic. Apex Chert controversy. The Apex Chert microfossils were originally described as septate filaments composed of kerogen similar in morphology to Proterozoic and modern cyanobacteria. However new thin section analysis shows that these carbonaceous structures are not simple filaments. Many of the original microfossils are branched and have variable thickness when the plane of focus is changed. Hydrothermal alteration of organic remains has also been suggested for the creation of these strange morphologies. Another point of contention lies with the nature of the carbon material in these proposed microfossils. Kerogen is structurally amorphous, but transforms into well-ordered graphite under high pressures and temperatures. Raman spectrometry of the carbonaceous material in the proposed microfossils has been interpreted both as partially graphitized kerogen and amorphous graphite. However, these results are inconclusive, since Raman spectrometry cannot adequately discriminate between kerogen and disordered graphite. There are also opposing views for the origin of the carbon in the Apex Chert. The carbon would be biogenic if the proposed microfossils are indeed the remains of former living organisms. However, an inorganic Fischer- Tropsch-type synthesis is also a possible explanation for the formation of large-aggregate carbonaceous particles and could also account for the depletion of (13)C observed.

DeGregorio, B. T.↗
NASA NTRS2006

Using Apex To Construct CPM-GOMS Models

process for automatically generating computational models of human/computer interactions as well as graphical and textual representations of the models has been built on the conceptual foundation of a method known in the art as CPM-GOMS. This method is so named because it combines (1) the task decomposition of analysis according to an underlying method known in the art as the goals, operators, methods, and selection (GOMS) method with (2) a model of human resource usage at the level of cognitive, perceptual, and motor (CPM) operations. CPM-GOMS models have made accurate predictions about behaviors of skilled computer users in routine tasks, but heretofore, such models have been generated in a tedious, error-prone manual process. In the present process, CPM-GOMS models are generated automatically from a hierarchical task decomposition expressed by use of a computer program, known as Apex, designed previously to be used to model human behavior in complex, dynamic tasks. An inherent capability of Apex for scheduling of resources automates the difficult task of interleaving the cognitive, perceptual, and motor resources that underlie common task operators (e.g., move and click mouse). The user interface of Apex automatically generates Program Evaluation Review Technique (PERT) charts, which enable modelers to visualize the complex parallel behavior represented by a model. Because interleaving and the generation of displays to aid visualization are automated, it is now feasible to construct arbitrarily long sequences of behaviors. The process was tested by using Apex to create a CPM-GOMS model of a relatively simple human/computer-interaction task and comparing the time predictions of the model and measurements of the times taken by human users in performing the various steps of the task. The task was to withdraw $80 in cash from an automated teller machine (ATM). For the test, a Visual Basic mockup of an ATM was created, with a provision for input from (and measurement of the performance of) the user via a mouse. The times predicted by the automatically generated model turned out to approximate the measured times fairly well (see figure). While these results are promising, there is need for further development of the process. Moreover, it will also be necessary to test other, more complex models: The actions required of the user in the ATM task are too sequential to involve substantial parallelism and interleaving and, hence, do not serve as an adequate test of the unique strength of CPM-GOMS models to accommodate parallelism and interleaving.

John, Bonnie↗
NASA NTRS1985

An exploratory study of apex fence flaps on a 74 deg delta wing

An exploratory wind tunnel investigation was performed to observe the flow field effects produced by vertically deployed apex fences on a planar 74 degree delta wing. The delta shaped fences, each comprising approximately 3.375 percent of the wing area, were affixed along the first 25 percent of the wing leading edge in symmetric as well as asymmetric (i.e., fence on one side only) arrangements. The vortex flow field was visualized at angles of attack from 0 to 20 degrees using helium bubble and oil flow techniques; upper surface pressures were also measured along spanwise rows. The results were used to construct a preliminary description of the vortex patterns and induced pressures associated with vertical apex fence deployment. The objective was to obtain an initial evaluation of the potential of apex fences as vortex devices for subsonic lift modulation as well as lateral directional control of delta wing aircraft.

Wahls, R. A.↗
NASA NTRS1980

Synoptic thermal and oceanographic parameter distribution in the New York Bight Apex on June 23, 1977

Concurrent surface water measurements made from a moving oceanographic research vessel were used to calibrate and interpret remotely sensed data collected over a plume in the New York Bight Apex on June 23, 1977. Multiple regression techniques were used to develop equations to subsequently map synoptic distributions of water quality parameters, chlorophyll A and total suspended matter, in the remotely sensed scene. Thermal (which did not have surface calibration values) and water quality parameter distributions indicated a cold mass of upwelled water in the Bight Apex with an overflowing nutrient-rich warm water plume that originated in the Sandy Hook Bay and flowed south near the New Jersey shoreline. Additional comparison of remotely sensed thermal and optical properties of the water with shipboard measurements indicated that remotely sensed data may be particularly useful for studying physical and biological processes in the top several meters of surface water at the plume boundaries.

Johnson, R. W.↗
NASA NTRS1981

Synoptic thermal and oceanographic parameter distributions in the New York Bight Apex

Concurrent surface water measurements made from a moving oceanographic research vessel were used to calibrate and interpret remotely sensed data collected over a plume in the New York Bight Apex on 23 June 1977. Multiple regression techniques were used to develop equations to map synoptic distributions of chlorophyll a and total suspended matter in the remotely sensed scene. Thermal (which did not have surface calibration values) and water quality parameter distributions indicated a cold mass of water in the Bight Apex with an overflowing nutrient-rich warm water plume that originated in the Sandy Hook Bay and flowed south near the New Jersey shoreline. Data analysis indicates that remotely sensed data may be particularly useful for studying physical and biological processes in the top several metres of surface water at plume boundaries.

Johnson, R. W.↗
NASA NTRS1985

An experimental investigation of apex fence flaps on delta wings

The effects on leading edge vortex formation produced by apex fences mounted on two delta wings were examined in a subsonic wind tunnel. Pressure data were collected on the upper surface of the test wings and oil flow and bubble flow visualizations were performed. The deflections studied were 74, 90 and 65 deg in one-sided and two-sided configurations. Full span and semi-span delta wing planforms were used. Relatively small, symmetrically deployed apex fences provided enhanced upper surface suction which, in some angle-of-attack situations, could lead to a pitch-up force. Asymmetrically-deployed fences showed promise for yaw control at high angles of attack, althouh the force effectiveness has yet to be quantified.

Vess, R. J.↗
NASA NTRS1998

Effect of Apex Flap Deflection on Vertical Tail Buffeting

A computational study of the effect of vortex breakdown location on vertical tail buffeting is conducted. The position of the breakdown is modified by employing an apex flap deflected by an experimentally determined optimal angle. The delayed breakdown flow and buffeting response is then compared to the nominal undeflected case. This multidisciplinary problem is solved sequentially for the fluid flow, the elastic tail deformations and the grid displacements. The fluid flow is simulated by time accurately solving the unsteady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, upwind, flux-difference splitting finite volume scheme. The elastic vibrations of the tails are modeled by uncoupled bending and torsion beam equations. These equations are solved accurately in time using the Galerkin method and a five-stage Runge-Kutta-Verner scheme. The grid for the fluid dynamics calculations is continuously deformed using interpolation functions to disperse the displacements smoothly throughout the computational domain. An angle-of-attack of 35 deg.is chosen such that the wing primary-vortex cores experience vortex breakdown and the resulting turbulent wake flow impinges on tile vertical tails. The dimensions and material properties of the vertical tails are chosen such that the deflections are large enough to insure interaction with the flow, and the natural frequencies are high enough to facilitate a practical computational solution. Results are presented for a baseline uncontrolled buffeting case and a delayed breakdown case in which the apex flap has been deflected 15 deg. The flap was found to be very effective in delaying the breakdown, increasing the location from 50%c to 94%c, which resulted in a 6% increase in lift coefficient and pitching moment. However, the integrated buffet loads and tip responses were roughly equivalent for the two cases.

Massey, Steven J.↗
NASA NTRS1998

Numerical Simulations of Unsteady Low-Reynolds-Number Flows Over the APEX Airfoil

Laminar and transitional separation bubbles are an important feature of low-Reynolds-number flows over airfoils. The separation bubbles are unsteady and have a significant impact on the aerodynamic properties of the airfoils. In this paper unsteady low-Reynolds-number separated flows over the APEX airfoil are calculated using a Navier-Stokes solver. The numerical results show the presence of unsteady separation bubbles in the flowfield. An analysis of the numerical results shows that flowfield disturbances are amplified significantly in the separation bubble, leading to periodic vortex shedding. A linear stability analysis of the separated boundary layer is performed and the results show that the dominant wavenumber and frequency in the numerical simulations agree with the most unstable wavenumber and frequency from the linear stability analysis. The numerical results also show the growth and interaction of disturbance waves in the separation bubble. For transonic flows over the APEX airfoil, the calculations show that the presence of shocks causes significant changes in the separation location and consequently, the overall flowfield.

Tatineni, Mahidhar↗
NASA NTRS1997

Improvements for Image Compression Using Adaptive Principal Component Extraction (APEX)

The issues of image compression and pattern classification have been a primary focus of researchers among a variety of fields including signal and image processing, pattern recognition, data classification, etc. These issues depend on finding an efficient representation of the source data. In this paper we collate our earlier results where we introduced the application of the. Hilbe.rt scan to a principal component algorithm (PCA) with Adaptive Principal Component Extraction (APEX) neural network model. We apply these technique to medical imaging, particularly image representation and compression. We apply the Hilbert scan to the APEX algorithm to improve results

Ziyad, Nigel A.↗
NASA NTRS1999

The Mars 2001 Athena Precursor Experiment (APEX)

The Athena Precursor Experiment (APEX) is a suite of scientific instruments for the Mars Surveyor Program 2001 (MSP'01) lander. The major elements of the APEX pay load are: (1) Pancam/Mini-TES, a combined stereo color imager and mid-infrared point spectrometer. (2) An Alpha-Proton-X-Ray Spectrometer (APXS) for in-situ elemental analysis. (3) A Mossbauer Spectrometer for in-situ determination of the mineralogy of Fe-bearing rocks and soils. (4) A Magnet Array that can separate magnetic soil particles from non-magnetic ones.

Squyres, S. W.↗