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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Designing Crane Controls with Applied Mechanical and Electrical Safety Features

The use of overhead traveling bridge cranes in many varied applications is common practice. In particular, the use of cranes in the nuclear, military, commercial, aerospace, and other industries can involve safety critical situations. Considerations for Human Injury or Casualty, Loss of Assets, Endangering the Environment, or Economic Reduction must be addressed. Traditionally, in order to achieve additional safety in these applications, mechanical systems have been augmented with a variety of devices. These devices assure that a mechanical component failure shall reduce the risk of a catastrophic loss of the correct and/or safe load carrying capability. ASME NOG-1-1998, (Rules for Construction of Overhead and Gantry Cranes, Top Running Bridge, and Multiple Girder), provides design standards for cranes in safety critical areas. Over and above the minimum safety requirements of todays design standards, users struggle with obtaining a higher degree of reliability through more precise functional specifications while attempting to provide "smart" safety systems. Electrical control systems also may be equipped with protective devices similar to the mechanical design features. Demands for improvement of the cranes "control system" is often recognized, but difficult to quantify for this traditionally "mechanically" oriented market. Finite details for each operation must be examined and understood. As an example, load drift (or small motions) at close tolerances can be unacceptable (and considered critical). To meet these high functional demands encoders and other devices are independently added to control systems to provide motion and velocity feedback to the control drive. This paper will examine the implementation of Programmable Electronic Systems (PES). PES is a term this paper will use to describe any control system utilizing any programmable electronic device such as Programmable Logic Controllers (PLC), or an Adjustable Frequency Drive (AID) 'smart' programmable motion controller. Therefore the use of the term Programmable Electronic Systems (PES) is an encompassing description for a large spectrum of programmable electronic control devices.

Lytle, Bradford P.↗
NASA NTRS2001

Design of Unstructured Adaptive (UA) NAS Parallel Benchmark Featuring Irregular, Dynamic Memory Accesses

We describe the design of a new method for the measurement of the performance of modern computer systems when solving scientific problems featuring irregular, dynamic memory accesses. The method involves the solution of a stylized heat transfer problem on an unstructured, adaptive grid. A Spectral Element Method (SEM) with an adaptive, nonconforming mesh is selected to discretize the transport equation. The relatively high order of the SEM lowers the fraction of wall clock time spent on inter-processor communication, which eases the load balancing task and allows us to concentrate on the memory accesses. The benchmark is designed to be three-dimensional. Parallelization and load balance issues of a reference implementation will be described in detail in future reports.

Feng, Hui-Yu↗
NASA NTRS2002

Etching of Silicon in HBr Plasmas for High Aspect Ratio Features

Etching in semiconductor processing typically involves using halides because of the relatively fast rates. Bromine containing plasmas can generate high aspect ratio trenches, desirable for DRAM and MEMS applications, with relatively straight sidewalk We present scanning electron microscope images for silicon-etched trenches in a HBr plasma. Using a feature profile simulation, we show that the removal yield parameter, or number of neutrals removed per incident ion due to all processes (sputtering, spontaneous desorption, etc.), dictates the profile shape. We find that the profile becomes pinched off when the removal yield is a constant, with a maximum aspect ratio (AR) of about 5 to 1 (depth to height). When the removal yield decreases with increasing ion angle, the etch rate increases at the comers and the trench bottom broadens. The profiles have ARs of over 9:1 for yields that vary with ion angle. To match the experimentally observed etched time of 250 s for an AR of 9:1 with a trench width of 0.135 microns, we find that the neutral flux must be 3.336 x 10(exp 17)sq cm/s.

Hwang, Helen H.↗
NASA NTRS1998

Feature Extraction of Event-Related Potentials Using Wavelets: An Application to Human Performance Monitoring

This report describes the development and evaluation of mathematical models for predicting human performance from discrete wavelet transforms (DWT) of event-related potentials (ERP) elicited by task-relevant stimuli. The DWT was compared to principal components analysis (PCA) for representation of ERPs in linear regression and neural network models developed to predict a composite measure of human signal detection performance. Linear regression models based on coefficients of the decimated DWT predicted signal detection performance with half as many f ree parameters as comparable models based on PCA scores. In addition, the DWT-based models were more resistant to model degradation due to over-fitting than PCA-based models. Feed-forward neural networks were trained using the backpropagation,-, algorithm to predict signal detection performance based on raw ERPs, PCA scores, or high-power coefficients of the DWT. Neural networks based on high-power DWT coefficients trained with fewer iterations, generalized to new data better, and were more resistant to overfitting than networks based on raw ERPs. Networks based on PCA scores did not generalize to new data as well as either the DWT network or the raw ERP network. The results show that wavelet expansions represent the ERP efficiently and extract behaviorally important features for use in linear regression or neural network models of human performance. The efficiency of the DWT is discussed in terms of its decorrelation and energy compaction properties. In addition, the DWT models provided evidence that a pattern of low-frequency activity (1 to 3.5 Hz) occurring at specific times and scalp locations is a reliable correlate of human signal detection performance.

Trejo, Leonard J.↗
NASA NTRS2001

Spinoff 2001: Special Millennium Feature

For the past 43 years, NASA has devoted its facilities, labor force, and expertise to sharing the abundance of technology developments used for its missions with the nation's industries. These countless technologies have not only successfully contributed to the growth of the U.S. economy, but also to the quality of life on Earth. For the past 25 years, NASA's Spinoff publication has brought attention to thousands of technologies, products, and services that were developed as a direct result of commercial partnerships between NASA and the private business sector. Many of these exciting technologies included advances in ceramics, computer technology, fiber optics, and remote sensing. New and ongoing research at the NASA field centers covers a full spectrum of technologies that will provide numerous advantages for the future, many of which have made significant strides in the commercial market. The NASA Commercial Technology Network plays a large role in transferring this progress. By applying NASA technologies such as data communication, aircraft de-icing technologies, and innovative materials to everyday functions, American consumers and the national economy benefit. Moving forward into the new millennium, these new technologies will further advance our country's position as the world leader in scientific and technical innovation. These cutting-edge innovations represent the investment of the U.S. citizen in the Space Program. Some of these technologies are highlighted in Spinoff 2001, an example of NASA's commitment to technology transfer and commercialization assistance. This year's issue spotlights the commercial technology efforts of NASA's John F. Kennedy Space Center. Kennedy's extensive network of commercial technology opportunities has enabled them to become a leader in technology transfer outreach. This kind of leadership is exemplified through Kennedy's recent partnership with the State of Florida, working toward the development of the Space Experiment Research and Processing Laboratory. The new laboratory is the first step toward the development of a proposed 400-acre Space Commerce Park, located at Kennedy Space Center. Spinoff, once again, successfully showcases the variety of commercial successes and benefits resulting from the transfer of NASA technology to private industry. It is with great pride and pleasure that we present Spinoff 2001 with a Special Millennium Feature. With help from U.S. industry and commercial technology programs, NASA will continue to assist in the presentation of innovative new products to our nation.

Source record↗
NASA NTRS2002

Observational Signatures of Black Holes: Spectral and Temporal Features of XTE J1550-564

The theoretical predictions of the converging inflow, or Bulk-Motion Comptonization model are discussed and some predictions are compared to X- and gamma-ray observations of the high-soft state of Galactic black hole candidate XTE J1550+564. The approx. 10(exp 2)-Hz QPO phenomenon tends to be detected in the high-state at times when the bolometric luminosity surges and the hard-powerlaw spectral component is dominant. Furthermore, the power in these features increases with energy. We offer interpretation of this phenomenon, as oscillations of the innermost part of the accretion disk, which in turn supplies the seed photons for the converging inflow where the hard power-law is formed through Bulk Motion Comptonization (BMC). We further argue that the noted lack of coherence between intensity variations of the high-soft-state low and high energy bands is a natural consequence of our model, and that a natural explanation for the observed hard and soft lag phenomenon is offered. In addition, we address some criticisms of the BMC model supporting our claims with observational results.

Titarchuk, Lev↗
NASA NTRS1999

LIC for Surface Flow Feature Detection

The Line Integral Convolution (LIC) algorithm has received a lot of attention and interest. Yet, only a few of the current LIC related algorithms deal specifically with color textures for automatic detection of flow features. This paper provides an overview of research in this area.

Kao, David L.↗
NASA NTRS2002

A Sublimation Model for the Martian Polar Swiss-Cheese Features. Observational and Modeling Studies of the South Polar Residual Cap

In their pioneering work Leighton and Murray argued that the Mars atmosphere, which is 95 percent CO2 today, is controlled by vapor equilibrium with a much larger polar reservoir of solid CO2. Here we argue that the polar reservoir is small and cannot function as a long-term buffer to the more massive atmosphere. Our work is based on modeling the circular depressions (Swiss-cheese features) in the south polar cap. We argue that a solid CO2 layer approximately 8 meters thick is being etched away to reveal water ice underneath. Preliminary results from the THEMIS (Thermal Emission Imaging System) instrument seem to confirm our model.

Byrne, Shane↗
NASA NTRS2000

Geological History of the Tyre Region of Europa: A Regional Perspective on Europan Surface Features and Ice Thickness

Galileo images of the Tyre Macula region of Europa at regional (170 m/pixel) and local (approx. 40 m/pixel) scales allow mapping and understanding of surface processes and landforms. Ridged plains, doublet and complex ridges, shallow pits, domes, "chaos" areas. impact structures, tilted blocks and massifs, and young fracture systems indicate a complex history of surface deformation on Europa. Regional and local morphologies of the Tyre region of Europa suggest that an impactor penetrated through several kilometers of water ice tc a mobile layer below. The surface morphology was initially dominated by formation of ridged plains, followed by development of ridge bands and doublet ridges, with chaos and fracture formation dominating the latter part of the geologic history of the Tyre region. Two distinct types of chaos have been identified which, along with upwarped dome materials, appear to represent a continuum of features (domes-play chaos-knobby chaos) resulting from increasing degree of surface disruption associated with local lithospheric heating and thinning. Local and regional stratigraphic relationships, block heights, and the morphology of the Tyre impact structure suggest the presence of low-viscosity ice or liquid water beneath a thin (severa1 kilometers) surface ice shell at the time of the impact. The very low impact crater density on the surface of Europa suggests that this thin shell has either formed or been thoroughly resurfaced in the very recent past.

Kadel, Steven D.↗
NASA NTRS2002

Universal Features of the Fluid to Solid Transition for Attractive Colloidal Particles

Attractive colloidal particles can exhibit a fluid to solid phase transition if the magnitude of the attractive interaction is sufficiently large, if the volume fraction is sufficiently high, and if the applied stress is sufficiently small. The nature of this fluid to solid transition is similar for many different colloid systems, and for many different forms of interaction. The jamming phase transition captures the common features of these fluid to solid translations, by unifying the behavior as a function of the particle volume fraction, the energy of interparticle attractions, and the applied stress. This paper describes the applicability of the jamming state diagram, and highlights those regions where the fluid to solid transition is still poorly understood. It also presents new data for gelation of colloidal particles with an attractive depletion interaction, providing more insight into the origin of the fluid to solid transition.

Cipelletti, L.↗
NASA NTRS2003

Nanolayered Features of Collagen-like Peptides

We have been investigating collagen-like model oligopeptides as molecular bases for complex ordered biomimetic materials. The collagen-like molecules incorporate aspects of native collagen sequence and secondary structure. Designed modifications to native primary and secondary structure have been incorporated to control the nanostructure and microstructure of the collagen-like materials produced. We find that the collagen-like molecules form a number of lyotropic rod liquid crystalline phases, which because of their strong temperature dependence in the liquid state can also be viewed as solvent intercalated thermotropic liquid crystals. The liquid crystalline phases formed by the molecules can be captured in the solid state by drying off solvent, resulting in solid nanopatterned (chemically and physically) thermally stable (to greater than 100 C) materials. Designed sequences which stabilize smectic phases have allowed a variety of nanoscale multilayered biopolymeric materials to be developed. Preliminary investigations suggest that chemical patterns running perpendicular to the smectic layer plane can be functionalized and used to localize a variety of organic, inorganic, and organometallic moieties in very simple multilayered nanocomposites. The phase behavior of collagen-like oligopeptide materials is described, emphasizing the correlation between mesophase, molecular orientation, and chemical patterning at the microscale and nanoscale. In many cases, the textures observed for smectic and hexatic phase collagens are remarkably similar to the complex (and not fully understood) helicoids observed in biological collagen-based tissues. Comparisons between biological morphologies and collagen model liquid crystalline (and solidified materials) textures may help us understand the molecular features which impart order and function to the extracellular matrix and to collagen-based mineralized tissues. Initial studies have utilized synthetic collagen-like peptides while future work will also focus on similar sequences generated via genetic engineering methods.

Valluzzi, Regina↗
NASA NTRS2003

Design Features and Capabilities of the First Materials Science Research Rack

The First Materials Science Research Rack (MSRR-1) aboard the International Space Station (ISS) will offer many unique capabilities and design features to facilitate a wide range of materials science investigations. The initial configuration of MSRR-1 will accommodate two independent Experiment Modules (EMS) and provide the capability for simultaneous on-orbit processing. The facility will provide the common subsystems and interfaces required for the operation of experiment hardware and accommodate telescience capabilities. MSRR1 will utilize an International Standard Payload Rack (ISPR) equipped with an Active Rack Isolation System (ARIS) for vibration isolation of the facility.

Pettigrew, P. J.↗
NASA NTRS2003

Search for X-ray Spectral Features in Two BL Lac Objects

This grant covered the analysis and interpretation of astrophysical data obtained with the XMM-Newton satellite mission. BL Lac objects are active galactic nuclei that exhibit unusually strong polarization and variability, and are also missing the usual strong optical/ultraviolet emission lines. They are typically strong X-ray sources, but this is the first survey gathering high-quality spectral data from a significant number of these objects. The observations were successful, and all data (for objects in this proposal as well as that of Dr. Perlman s) were of very good quality, as expected. We find that the X-ray spectra of most of these objects are well described by a power-law after allowing for low-energy absorption that can be attributed to neutral gas in the line of sight, presumably located in our own Galaxy. However, in some cases we see indications of a deviation from power-law behavior in the sense that the spectrum appears to be steepening (softening) to higher energies. We are developing a theoretical model in which the steepening is a result of energy-dependent cooling of the radiating particles.We searched for discrete spectral features that might be intrinsic to the objects or their host galaxies, but we found none at the level of sensitivity provided by these data. These are interestingly strong upper bounds.

Source record↗
NASA NTRS2003

Use of Multi-Resolution Wavelet Feature Pyramids for Automatic Registration of Multi-Sensor Imagery

The problem of image registration, or alignment of two or more images representing the same scene or object, has to be addressed in various disciplines that employ digital imaging. In the area of remote sensing, just like in medical imaging or computer vision, it is necessary to design robust, fast and widely applicable algorithms that would allow automatic registration of images generated by various imaging platforms at the same or different times, and that would provide sub-pixel accuracy. One of the main issues that needs to be addressed when developing a registration algorithm is what type of information should be extracted from the images being registered, to be used in the search for the geometric transformation that best aligns them. The main objective of this paper is to evaluate several wavelet pyramids that may be used both for invariant feature extraction and for representing images at multiple spatial resolutions to accelerate registration. We find that the band-pass wavelets obtained from the Steerable Pyramid due to Simoncelli perform better than two types of low-pass pyramids when the images being registered have relatively small amount of nonlinear radiometric variations between them. Based on these findings, we propose a modification of a gradient-based registration algorithm that has recently been developed for medical data. We test the modified algorithm on several sets of real and synthetic satellite imagery.

Zavorin, Ilya↗
NASA NTRS2003

Mars: Detaching of the Free Water Signature (FWS) Presence Regions on the Base of HEND/ODYSSEY Data and Their Correlation with Some Permafrost Features from MOC Data

The first results from global mapping of the neutron albedo from Mars by HEND instrument have shown the noticeable deficit of both the epithermal (EN) and the fast (FN) neutrons counts rate in the high latitudes regions of both hemispheres of the planet. The deficit is indicative for high enriching of the surface regolith by hydrogen, which may correspond to amount of any water phases and forms. The objectives of our study are the spatial and temporal variations of the free water (ice) signature in the Martian surface layer on the base of HEND/ODYSSEY data and their correlation with spatial spreading of some permafrost features, mapped on the base of MOC images. For the study we used the results of the global mapping (pixel 5 x5 ) of EN and FN albedo, realized by HEND/ODYSSEY in the period from 17 February to 10 December 2002 year.

Kuzmin, R. O.↗
NASA NTRS2003

Extraction of Qualitative Features from Sensor Data Using Windowed Fourier Transform

In this paper, we use Matlab to model the health monitoring of a system through the information gathered from sensors. This implies assessment of the condition of the system components. Once a normal mode of operation is established any deviation from the normal behavior indicates a change. This change may be due to a malfunction of an element, a qualitative change, or a change due to a problem with another element in the network. For example, if one sensor indicates that the temperature in the tank has experienced a step change then a pressure sensor associated with the process in the tank should also experience a step change. The step up and step down as well as sensor disturbances are assumed to be exponential. An RC network is used to model the main process, which is step-up (charging), drift, and step-down (discharging). The sensor disturbances and spike are added while the system is in drift. The system is allowed to run for a period equal to three time constant of the main process before changes occur. Then each point of the signal is selected with a trailing data collected previously. Two trailing lengths of data are selected, one equal to two time constants of the main process and the other equal to two time constants of the sensor disturbance. Next, the DC is removed from each set of data and then the data are passed through a window followed by calculation of spectra for each set. In order to extract features the signal power, peak, and spectrum are plotted vs time. The results indicate distinct shapes corresponding to each process. The study is also carried out for a number of Gaussian distributed noisy cases.

Amini, Abolfazl M.↗