Analysis of irrational transfer functions for distributed-parameter systems
Algorithmic and digital computer method for approximating irrational transfer functions by rational functions in control systems
Chen, C.-F.↗
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An example of age dependency in compartmental analysis
Compact analytic solution to distribution theory of nonsteady state model illustrated with biological data - age dependency in compartmental analysis
Matis, J. H.↗
Periodic analysis of total ozone and its vertical distribution
Both total ozone and vertical distribution ozone data from the period 1957 to 1972 are analyzed. For total ozone, improved monthly zonal means for both hemispheres are computed by weighting individual station monthly means by a factor which compensates for the close grouping of stations in certain regions of latitude bands. Longitudinal variability show maxima in summer in both hemispheres, but, in winter, only in the Northern Hemisphere. The geographical distributions of the long term mean, and the annual, quasibiennial and semiannual waves in total ozone over the Northern Hemisphere are presented. The extratropical amplitude of the annual wave is by far the largest of the three, as much as 120 m atm cm over northern Siberia. There is a tendency for all three waves to have maxima in high latitudes. Monthly means of the vertical distribution of ozone determined from 3 to 8 years of ozonesonde data over North America are presented. Number density is highest in the Arctic near 18 km. The region of maximum number density slopes upward toward 10 N, where the long term mean is 45 x 10 to the 11th power molecules cm/3 near 26 km.
Wilcox, R. W.↗
A preliminary analysis of lunar extra-mare basalts - Distribution, compositions, ages, volumes, and eruption styles
Extra-mare basalts occupy 8.5% of the lunar basalt area and comprise 1% of the total mare basalt volume. They are preferentially located where the crust is thin and topographically low. In terms of age, eruption style, and composition they are as variable as the mare basalts. In some instances extrusion in extra-mare craters was preceded by floor-fracturing whereas in other cases it apparently was not. The volume of lava erupted may have been controlled more by the volume of magma produced than by hydrostatic effects. A minimum of nearly 1300 separate basalt eruptions is indicated; the true value could be nearer 30,000 separate eruptions.
Whitford-Stark, J. L.↗
System analysis for the Huntsville Operational Support Center distributed computer system
A simulation model was developed and programmed in three languages BASIC, PASCAL, and SLAM. Two of the programs are included in this report, the BASIC and the PASCAL language programs. SLAM is not supported by NASA/MSFC facilities and hence was not included. The statistical comparison of simulations of the same HOSC system configurations are in good agreement and are in agreement with the operational statistics of HOSC that were obtained. Three variations of the most recent HOSC configuration was run and some conclusions drawn as to the system performance under these variations.
Ingels, E. M.↗
Definition, analysis and development of an optical data distribution network for integrated avionics and control systems. Part 2: Component development and system integration
Fiber optic transmission is emerging as an attractive concept in data distribution onboard civil aircraft. Development of an Optical Data Distribution Network for Integrated Avionics and Control Systems for commercial aircraft will provide a data distribution network that gives freedom from EMI-RFI and ground loop problems, eliminates crosstalk and short circuits, provides protection and immunity from lightning induced transients and give a large bandwidth data transmission capability. In addition there is a potential for significantly reducing the weight and increasing the reliability over conventional data distribution networks. Wavelength Division Multiplexing (WDM) is a candidate method for data communication between the various avionic subsystems. With WDM all systems could conceptually communicate with each other without time sharing and requiring complicated coding schemes for each computer and subsystem to recognize a message. However, the state of the art of optical technology limits the application of fiber optics in advanced integrated avionics and control systems. Therefore, it is necessary to address the architecture for a fiber optics data distribution system for integrated avionics and control systems as well as develop prototype components and systems.
Yen, H. W.↗
ISAAC (integrated Structural Analysis and Control) via Continuum Modeling and Distributed Frequency Domain Design Techniques
A methodology is proposed for the integrated design of structures and their controls. The integration of design is accomplished through simultaneous selection, via optimization, of designer-specified parameters governing the structure and its controller. The cost function is chosen to address the primary structural and control goals. Inequality constraints are added to insure that additional design requirements are met. The methodology is illustrated through development of an example involving a cantilever beam. A distributed transfer function is derived from the Bernoulli-Euler beam equation. A controller parameterization is then chosen, and performance requirements specified. A controller is then obtained via optimization, which is shown to give good performance.
Gustafson, C. L.↗
Asteroid rotation rates - Distributions and statistics
An analysis of asteroid rotation rates and light-curve amplitudes disclosed many significant correlations between these rotation parameters and asteroid diameter, with distinct changes occurring near 125 km, a diameter above which self-gravity may become important. It is suggested that this size range may represent a division between surviving primordial asteroids and collisional fragments. A comparison of rotational parameters between family and nonfamily asteroids showed that the Koronis and Eos families exhibit noticeable differences, considered to be due to different impact conditions and/or to a relatively younger age for the Koronis family.
Binzel, Richard P.↗
Statistical analysis of upflowing ion beam and conic distributions at DE 1 altitudes
Upflowing ion (UFI), beam, conic, and hybrid pitch angle distribution data obtained in the 8000-23,000-km altitude range by the energetic ion composition spectrometer of the DE 1 satellite during September 1981-June 1986 have been statistically analyzed. It is found that the source and transport mechanisms largely confine UFI to auroral field lines; no obvious one-to-one relationship is found between current direction and UFI source characteristics. O(+) is more efficiently accelerated than H(+) at the higher K(p) values.
Kondo, T.↗
Analysis of a general circulation model. II - Distribution of kinetic energy in the South Atlantic and Kuroshio/Oyashio systems
It was found (Garzoli et al., 1992) that the general circulation model of Semtner and Chervin (1992) provides accurate descriptions of the Brazil-Malvinas and the Kuroshio/Oyashio confluence systems, except for the fact that the model prediction shows less variability than that present in observations. This paper investigates the problem of model variability by analyzing the mean and the eddy kinetic energy from the model and comparing the values with the Geosat altimeter observations for the South Atlantic Ocean and for the Kuroshio system. It is found that, while the model shows transient eddy activity in the areas that overlap the Geosat observations, the energy level of the model transient motions is considerably smaller following an arch along the bottom topography. The same was found from the comparisons made with values obtained from FGGE and surface drifters. It is suggested that the model is poorly resolving instabilities in the confluence front, and is not resolving other transients appearing in regions of marked topography.
Garraffo, Zulema↗
An Analysis of Surface Pressures and Aerodynamic Load Distribution over the Swept Wing of the Douglas D-558-II Research Airplane at Mach Numbers from 0.73 to 1.73
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Taillon, Norman V↗
Comparative hypsometric analysis of both Earth and Venus topographic distributions
Previous studies have compared the global topographic distribution of both planets by means of differential hypsometric curves. For the purpose of comparison, the terrestrial oceanic load was removed, and a reference base level was acquired. It was chosen on the basis of geometric considerations and reflected the geometric shape of the mean dynamical equilibrium figure of the planetary surface in both cases. This reference level corresponds to the well-known sea level for the Earth; for Venus, given its slow rate of rotation, a sphere of radius close to the mean, median and modal values of the planetary radii distribution were considered and the radius value of 6051 km arbitrarily taken. These studies were based on the low resolution (100 x 100 sq km) coverage of Venus obtained by the Pioneer Venus altimeter and on the 1 deg x 1 deg terrestrial topography. But, apart from revealing the distinct contrast existing between the Earth's bimodal and Venus' strong unimodal topographic distribution, the choice of such a reference level is inadequate and even misleading for the comparative geophysical understanding of the planetary relief distribution. The present work reinvestigates the comparison between Earth and Venus hypsometric distribution on the basis of the high-resolution data provided, on one hand, by the recent Magellan global topographic coverage of Venus' surface, and on the other hand, by the detailed NCAR 5 x 5 ft. grid topographic database currently available for the Earth's surface.
Rosenblatt, P.↗
Distributive On-line Processing, Visualization and Analysis System for Gridded Remote Sensing Data
The ability to use data stored in the current Earth Observing System (EOS) archives for studying regional or global phenomena is highly dependent on having a detailed understanding of the data's internal structure and physical implementation. Gaining this understanding and applying it to data reduction is a time- consuming task that must be undertaken before the core investigation can begin. This is an especially difficult challenge when science objectives require users to deal with large multi-sensor data sets that are usually of different formats, structures, and resolutions, for example, when preparing data for input into modeling systems. The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) has taken a major step towards meeting this challenge by developing an infrastructure with a Web interface that allows users to perform interactive analysis online without downloading any data, the GES-DISC Interactive Online Visualization and Analysis Infrastructure or "Giovanni." Giovanni provides interactive, online, analysis tools for data users to facilitate their research. There have been several instances of this interface created to serve TRMM users, Aerosol scientists, Ocean Color and Agriculture applications users. The first generation of these tools support gridded data only. The user selects geophysical parameters, area of interest, time period; and the system generates an output on screen in a matter of seconds. The currently available output options are: Area plot averaged or accumulated over any available data period for any rectangular area; Time plot time series averaged over any rectangular area; Time plots image view of any longitude-time and latitude-time cross sections; ASCII output for all plot types; Image animation for area plot. In the future, we will add correlation plots, GIS-compatible outputs, etc. This allow user to focus on data content (i.e. science parameters) and eliminate the need for expensive learning, development and processing tasks that are redundantly incurred by an archive's user community. The current implementation utilizes the GrADS-DODS Server (GDS), a stable, secure data server that provides subsetting and analysis services across the Internet for any GrADS-readable dataset. The subsetting capability allows users to retrieve a specified temporal and/or spatial subdomain from a large dataset, eliminating the need to download everything simply to access a small relevant portion of a dataset. The analysis capability allows users to retrieve the results of an operation applied to one or more datasets on the server. In our case, we use this approach to read pre-processed binary files and/or to read and extract the needed parts from HDF or HDF-EOS files. These subsets then serve as inputs into GrADS processing and analysis scripts. It can be used in a wide variety of Earth science applications: climate and weather events study and monitoring; modeling. It can be easily configured for new applications.
Leptoukh, G.↗
Analysis of the Effects of Streamwise Lift Distribution on Sonic Boom Signature
The streamwise lift distribution of a wing-canard-stabilator-body configuration was varied to study its effect on the near-field sonic boom signature. The investigation was carried out via solving the three-dimensional Euler equation with the OVERFLOW-2 flow solver. The computational meshes were created using the Chimera overset grid topology. The lift distribution was varied by first deflecting the canard then trimming the aircraft with the wing and the stabilator while maintaining constant lift coefficient of 0.05. A validation study using experimental results was also performed to determine required grid resolution and appropriate numerical scheme. A wide range of streamwise lift distribution was simulated. The result shows that the longitudinal wave propagation speed can be controlled through lift distribution thus controlling the shock coalescence.
Yoo, Seung Yeun (Paul)↗
Advanced Symbolic Analysis Tools for Fault-Tolerant Integrated Distributed Systems
The project aims to develop advanced model-checking algorithms and tools to automate the verification of fault-tolerant distributed systems for avionics. We present a new method called Property-Directed K-Induction (PD-KIND) for synthesizing K-inductive invariants of state-transition systems. PD-KIND builds upon Satifiability Modulo Theories (SMT) to generalize Bradley's IC3 method and its variants. This method is implemented in a new tool called SALLY. Case studies show that PD-KIND can automatically verify fault-tolerant algorithms under a variety of fault models and that SALLY is competitive with other SMT-based model checkers.
Dutertre, Bruno↗
Distribution of Extraterrestrial Nucleobases, Other N-Heterocycles, and Their Precursors in A Sample From Asteroid Bennu
The recent discovery of all five canonical nucleobases in samples from Bennu provides compelling evidence that some of life’s ingredients were synthesized abiotically in the parent body of this asteroid and/or its precedent components. However, due to the sample availability and the limited method for the analysis, the detailed distribution of nucleobases in the samples remains elusive. Here we report the concentrations of a diverse suite of nitrogen (N)-heterocycles including nucleobases extracted by 2% and 20% hydrochloric acid from a homogenized Bennu sample. The detection of both canonical and non-canonical nucleobase pairs confirms that these biologically important compounds are extraterrestrial. Pyrimidines are more abundant than purines—like the Orgueil meteorite, but unlike the Murchison meteorite and asteroid Ryugu samples—suggesting preferential synthesis in ammonia-rich ices from the outer Solar System. The distribution of other N-heterocycles is consistent with extensive aqueous alteration on the parent body. High concentrations of urea underscore its role in N-heterocycle synthesis. Our findings offer important information on the prebiotic inventory of N-heterocycles in the Solar System.
Yasuhiro Oba↗
Simultaneous Development and Robust Optimization of a Microstructure Dependent Material
Recent microstructure characterization techniques combined with Symbolic Regression(SR)analysis has been proven to generate white box plasticity models well suited for incorporation into FEA software.The current work builds upon those efforts and demonstrates the applicability of Sequential Monte-Carlo (SMC) methods within SR analysis to condense model development and robust optimization into a single, co-dependent process. In this project, SMC methods provide a mechanism through which the observed microstructure features and associated variability can be incorporated into the discovery phase of model development and simultaneously recover approximate parameter distributions through SR analysis. The demonstration utilized a data set consisting of tensile test results from a limited number of sample specimens with corresponding EBSD data from which microstructure features were characterized.The maximum threshold stress model in the Visco-Plastic Self-Consistent (VPSC) code developed by Los Alamos National Laboratories was calibrated using mechanical test data.Synthetic volume elements with statistically equivalent microstructure were generated with DREAM3Dbased on the observed EBSD data. VPSC was used to simulate the corresponding tensile test response for each of the synthetic volume elements. The simulated microstructure and tensile test data was used astraining datafor SMC-SR algorithm and the resulting model was validated with data from the original empirical data set.
Karl Garbrecht↗
An analysis for high speed propeller-nacelle aerodynamic performance prediction. Volume 1: Theory and application
A computer program, the Propeller Nacelle Aerodynamic Performance Prediction Analysis (PANPER), was developed for the prediction and analysis of the performance and airflow of propeller-nacelle configurations operating over a forward speed range inclusive of high speed flight typical of recent propfan designs. A propeller lifting line, wake program was combined with a compressible, viscous center body interaction program, originally developed for diffusers, to compute the propeller-nacelle flow field, blade loading distribution, propeller performance, and the nacelle forebody pressure and viscous drag distributions. The computer analysis is applicable to single and coaxial counterrotating propellers. The blade geometries can include spanwise variations in sweep, droop, taper, thickness, and airfoil section type. In the coaxial mode of operation the analysis can treat both equal and unequal blade number and rotational speeds on the propeller disks. The nacelle portion of the analysis can treat both free air and tunnel wall configurations including wall bleed. The analysis was applied to many different sets of flight conditions using selected aerodynamic modeling options. The influence of different propeller nacelle-tunnel wall configurations was studied. Comparisons with available test data for both single and coaxial propeller configurations are presented along with a discussion of the results.
Egolf, T. Alan↗