Prototype Data Research Articles

Diagnosing a Colorado Heavy Snow Event with a Nonhydrostatic Mesoscale Numerical Model Structured for Operational Use

Abstract State-of-the-art data sources, such as Doppler radar, automated surface observations, wind profiler, digital satellite, and aircraft reports, are for the first time providing the capability to generate real-time, operational three-dimensional gridded datasets with sufficient spatial and temporal resolutions to diagnose the structure and evolution of mesoscale systems. A prototype data assimilation system of this type, called the Local Analysis and Prediction System (LAPS), is being developed at the National Oceanic and Atmospheric Administration's Forecast Systems Laboratory. The investigation uses the three-dimensional LAPS analyses for initialization of the nonhydrostatic Regional Atmospheric Modeling System (RAMS) model developed at Colorado State University to create a system capable of generating operational mesoscale predictions. The LAPS/RAMS system structured for operational use can add significant value to existing operational model output and provide an improved scientific understanding...

Local Scour Downstream of Hydraulic Structures

An analysis of the problem of local scour downstream of hydraulic structures is presented here. This paper briefly discusses the functional design of the bed protection downstream of large hydraulic structures. Phases of the scour process and transport mechanism are treated in an introductory manner. Subsequently, semiempirical relations for the maximum scour depth of clear-water scour (scour with no sediment flux from upstream) and the stability analysis of scour slopes upstream are discussed. The proposed equations are verified with prototype data.

PREDICTING OXYGEN CONTENT DOWNSTREAM OF WEIRS, SPILLWAYS AND WATERWAYS.

At hydraulic structures (e.g. weirs, spillways), air-water transfer of atmospheric gases (e.g. oxygen) occurs by self-aeration along the chute and by flow aeration in the hydraulic jump at the downstream end of the structure. In this paper, experimental data are re-analysed and compared with a numerical method to predict the free-surface aeration. Aeration at hydraulic jumps is also examined and compared with existing correlations. Calculations of free-surface aeration and empirical correlations for hydraulic jump aeration are combined to predict the DO content downstream of weirs and spillways. Good agreement between calculations and prototype data is obtained. The results indicate that self-aeration might contribute to a large part of the oxygenation taking place at hydraulic structures for small water discharges. For large discharges, the reduction or the disappearance of free-surface aeration affects substantially the aeration efficiency.

HyperFile: A data and query model for documents

Non-quantitative information such as documents and pictures pose interesting new problems in the database world. Traditional data models and query languages do not provide appropriate support for this information. Such data are typically stored in file systems, which do not provide the security, integrity, or query features of database management systems. The hypertext model has emerged as a good interface to this information; however, finding information using hypertext browsing does not scale well. We developed a query interface that serves as an extension of the browsing model of hypertext systems. These queries minimize the repeated user interactions required to locate data in a standard hypertext system. HyperFile is a prototype data server interface. In this article, we describe HyperFile, including a number of issues such as query generation, query processing, and indexing.

Simulation of multi-species tropical forest dynamics using a vertically and horizontally structured model

The mutual interaction of forest growth and light conditions causes vertical and horizontal differentiation in the natural forest mosaic. The associated physical processes should be represented in simulation models describing long-term forest dynamics. The FORMIX2 (tropical) forest simulator incorporates the multi-storey canopy layer structure of the natural tropical forest, the basic processes of gap succession dynamics and gap interaction by tree fall and seed dispersal, several functionally different species groups (emergents, main canopy trees, pioneers, woody treelets and forest-floor herbs) and the energy (carbon) balance of assimilation, dissimilation, and increment resulting from the differing light conditions for the various canopy layers in the gap-size areas of a forest mosaic. The vertically and horizontally structured FORMIX2 model produces time-dependent results (average per hectare data) for stem numbers, diameter distributions, basal areas, standing crop and yield, as well as dynamic views of the forest profile and of spatial forest development, as a function of logging method and intensity and silvicultural treatment. The model has been applied in an exploratory investigation to compute the long-term development of (a) virgin forest and (b) logged-over forest in Sabah, using prototypical data. The results obtained agree with empirical data.

Development of a Hermetically Sealed Stirling Engine Battery Charger

Recent Stirling engine research at the University of Canterbury has focused on the development of a compact 12 volt 200 watt electrical battery charger suitable for use in yachts, mobile homes or remote dwellings, and intended for scaling up to larger power applications. The hermetically sealed engine with integral alternator uses a four-cylinder double-acting configuration with air pressurized to 1 MPa as the working fluid. The engine and battery charger control system includes self-regulation, and automatic start and shut-down. The previous paper has described the wobble yoke mechanism which is central to the engine design as it requires only pre-lubricated single degree of freedom bearings. This paper explains the design philosophy behind the new engine and describes the computer modelling and subsequent development of engine components on an alpha configuration experimental prototype. Features examined include the alternator, the cylinder-mounted seals and the heat exchangers. Embodiment design features of the final double-acting prototype are discussed. Performance data for the experimental prototype are presented.

Adaptive Controllers as Virtual Instruments

A virtual instrument environment is an ideal paradigm for building prototype data acquisition and control system. It offers several conventional components of instruments to acquire data from plug-in boards and programmable instruments and then analyze the data, control the process and present the results through graphical interfaces. One of the most advanced representation of this idea is the National Instruments’ LabView®. A new family of adaptive controllers were developed based on this system. This paper presents one of its elements, an adaptive PID controller in detail, where the delay time of the system is estimated with a new algorithm in the adaptation step.

A small Unix-based data acquisition system

The proposed SLAC B Factory detector plans to use Unix-based machines for all aspects of computing, including real-time data acquisition and experimental control. An R&D program has been established to investigate the use of Unix in the various aspects of experimental computation. Earlier R&D work investigated the basic real-time aspects of the IBM RS/6000 workstation running AIX, which claims to be a real-time operating system. The next step in this R&D is the construction of a prototype data acquisition system which attempts to exercise many of the features needed in the final on-line system in a realistic situation. For this project, we have combined efforts with a team studying the use of novel cell designs and gas mixtures in a new prototype drift chamber. >

Effects of bathymetric complexities and wind generation in a coastal wave propagation model

A new wave modelling strategy has been developed by Holthuijsen et al. (1989) for estimating wave heights for engineering applications in coastal areas. This strategy as well as the original model itself of Holthuijsen et al. (1989), called HISWA, are being used in several engineering applications. This paper examines two aspects of this model: its ability to adequately predict wave properties in regions with complex bathymetry where diffraction effects are likely to be important, and its ability to model wave growth due to wind. The former is of interest because the model is based on the energy-balance equation and does not explicitly incorporate diffraction. Other such models deal with this through artificial bounds on the energy, whereas HISWA does not. It is therefore necessary for the engineer to be aware of its performance in such situations. Investigations are therefore performed using hydraulic model data and the results of other mathematical models that are known to adequately handle such bathymetric configurations. For complex bathymetries, the model is found to give good simulations for sea-states with considerable directional spreading. As the degree of spreading decreased or for certain special wave conditions, model performance was marginal. Finally, the model is used to study the physics of wave decay and wind-induced growth in Saginaw Bay (Michigan) using prototype data.

Scalable software libraries

Many software libraries (e.g., the Booch C++ Components, libg++, NIHCL, COOL) provide components (classes) that implement data structures. Each component is written by hand and represents a unique combination of features (e.g. concurrency, data structure, memory allocation algorithms) that distinguishes it from other components.We argue that this way of building data structure component libraries is inherently unscalable. Libraries should not enumerate complex components with numerous features; rather, libraries should take a minimalist approach: they should provide only primitive building blocks and be accompanied by generators that can combine these blocks to yield complex custom data structures.In this paper, we describe a prototype data structure generator and the building blocks that populate its library. We also present preliminary experimental results which suggest that this approach does not compromise programmer productivity nor the run-time performance of generated data structures.

A feasibility study of a data acquisition system for a silicon strip detector with a digital readout scheme

We describe a prototype data acquisition system for a silicon strip detector, which has been developed in terms of a digital readout scheme. The system consists of a master timing generator, readout controller, and a detector emulator card on which we use custom VLSI shift registers with operating clock frequency of 30 MHz.

Design and Implementation of a Prototype Data System for Earth Radiation Budget, Cloud, Aerosol, and Chemistry Data

Activities at the NASA Langley Research Center's distributed active archive centers (DAACs) intended to capitalize on existing centers of scientific expertise and to prevent a single point of failure are described. A Version 0 Langley DAAC, a prototype of an Earth Observing System Data and Information System, started archiving and distributing existing datasets on the earth's radiation budget, clouds, aerosols, and tropospheric chemistry in late 1992. The major goals of the LaRC Version 0 effort include to enhance scientific use of existing data; to develop institutional expertise in maintaining and distributing data; to encourage cooperative interagency and international involvement with datasets and research; and to use institutional capability for processing data from previous missions to prepare for processing the future EOS satellite data.

Developing Feature-based Manufacturing Applications Using PDES/STEP

This paper provides an object-onented approach to implement the PDES/STEP-based information model for concurrent engin eering applications. The PDES/STEP-based information model is the global foundation of concurrent engineering communication. To demonstrate the approach, a schema for assembly operations is defined, using the EXPRESS language, in the form of a prototype data model. The assembly_model entity is designed to carry the assembly system configuration information: bill of material (BOM) and assembly sequence. The assembly entities, called joints, are designed to work with each component part's PDES/STEP geometry, form feature, and tolerance definition. The connectivity of each joint is directly related to mating or joining parts' assembly-related form features. Examples are given to illustrate the use of PDES/STEP entities to construct the feature- based part definition and proposed assembly schema. The assembly schema is translated into the classes that both C++ and ROSE (an object-oriented database designed to support concurrent engineering and work with PDES/STEP) can accept. The classes serve as object templates for both application programs and ROSE, which has the capability to output the object in a STEP file format. The assembly functions and constraints related to the assembly entities are also defined to represent the dynamic properties of assembly schema.

The horizontal density gradient in hydrodynamic models of salinity around river mouths

Research described in this paper looks at the effect of horizontal density gradient in the vicinity of a river mouth. The model results based on the measured prototype data in Apalachicola Bay, Florida, indicate that horizontal density in the vicinity of a river mouth. The horizontal density gradient terms have been added to a two-dimensional depth averaged model and a two-layer hydrodynamic and salinity model. The salinity results from model with and without the horizontal density gradient terms are presented and compared with prototype data. The statistical analysis of salinity variance at each gage station around the river mouth also demonstrates the effect of the horizontal salinity gradients.

Real time data acquisition in SETI

NASA's Search for Extraterrestrial Intelligence presents unique challenges for data acquisition and analysis. During the proposed Microwave Observing Project each MultiChannel Spectrum Analyser (MCSA) system will process more than 60 million bytes of information every second. To prevent a backlog of data and to avoid delays in the confirmation of potential signals, the data will be processed in real time with special purpose hardware and software. The software is required to control and coordinate the hardware systems and the data that they produce. The performance of the system must be continuously monitored to assure that the search achieves maximum sensitivity, minimum contamination by Radio Frequency Interference, and optimal use of observing resources. We have developed a prototype data acquisition system that has been used in field tests of a prototype MCSA and software signal detection algorithms. The system, called VERA 2.0, is based on virtually concurrent communication software processes within a single computer. A new version under development will use several independent computers, communicating over a network. Each computer will be responsible for a portion of the data processing. Some techinques of artificial intelligence will be used to evaluate potential signals during the observation.

General Purpose High Temperature Microwave Measurement of Electromagnetic Properties

ABSTRACTAn efficient general purpose method has been developed for implementing a variety of broad band microwave measurement techniques at high temperature. Central to these techniques has been the development of a “dual-waveguide” test fixture. These techniques have been selected, out of necessity, to cover a variety of material types and geometries such as slabs, posts and sheets. These include measurement of complex permittivity and permeability using a modified Nicolson-Ross technique for slabs and Marcuwitz' algorithm for posts. In the implementation of the dual-waveguide, two adjacent and symmetric X-band waveguides are machined from a single block of Inconel alloy 601*, one serving as a test waveguide, the other as a reference waveguide. The dual-waveguide is surrounded by a programmable clam-shell furnace. The reference waveguide provides data which is used to compensate for electrical and dimensional thermal changes in the test section. Combined with commonly used HP 8510 Network Analyzer methods, automated test procedures have been developed to accommodate the various measurement types and sample shapes. Prototypical data will be presented illustrating the effectiveness of some of these techniques. The methods discussed are most useful for rapid data generation over temperatures ranging from room temperature to 2000 degrees F (1093 degrees C) and at frequencies defined by the waveguide dimensions. This paper highlights developments in the dual waveguide system since its construction over one year ago.

Accuracy of Offshore Subsidence Measurements With Seabed Pressure Gauges

Summary Phillips Petroleum Co. Norway pioneered the application of pressure gauges to measure offshore platform subsidence histories. Four pressure-gauge systems were installed in the Greater Ekofisk area. Prototype data prove that the progression of subsi dence can be measured with pressure gauges with a relative uncertainty of ±9 mm.

Numerical Computations of a Two-Layer Model for Estuaries

The research described in this paper is aimed at improving the predictive capability of numerical models for estuarine circulation. An improved two-layer model has been developed, which is applicable to the entire estuary including areas near the river mouth and the estuary inlet. This model is applied to Apalachicola Bay, Florida. The calibration and verification of the numerical model is accomplished with available prototype data. The horizontal density gradient terms have been added to the model and provide significantly improved salinity predictions near the river mouths. A theoretical approach to the internal wave boundary condition has been developed in this two-layer model.

Model for Turbidity Plume Induced by Bucket Dredge

A model based on the analytical solution of an advective-diffusion equation is developed to describe the turbidity plume induced by the operation of a bucket dredge. The model applies to the portion of the plume beyond the initial mixing zone where the separate patches of suspended sediments have coalesced into a continuous plume. It predicts the vertical average suspended sediment concentration within the plume as a function of the source strength of suspended sediment, the characteristics of the ambient flow field and the effective particle settling velocity. Four sets of field data from previous studies are compared with the model. It is shown that the model describes the qualitative feature of prototype data and that the calibrated model parameters agree with independent observations.

Horizontal Salinity Gradient Effects in Apalachicola Bay

This research demonstrates that horizontal density gradients approximated by salinity gradient represent an additional forcing term in the equations of motion, which have a significant effect in certain portions of a well‐mixed estuary. The horizontal density gradient terms have been added to a two‐dimensional depth‐averaged hydrodynamic and salinity model that is applied to Apalachicola Bay, Florida. A variable‐size finite difference cell is used in the model to allow more efficient resolution of physical details. The estuary system is assumed to be well mixed and boundary conditions are satisfied at the bottom and top of the water column but vertical components of velocity are neglected. A high‐resolution numerical model is desirable with particular emphasis on areas near passes, channels, and other critical features. This is accomplished by applying a smoothly varying grid technique. Results from the numerical model are presented and compared with prototype data. Calibration and verification of the improved numerical model is accomplished with available prototype data.