Showing papers by "Naval Postgraduate School published in 1989"

Decision, Estimation and Classification: An Introduction to Pattern Recognition and Related Topics

Abstract: Probability theory for random vectors simple statistical decision procedures operations upon random vectors feature extraction and nonlinear mapping quadratic and linear classifiers parameter estimation nonparametric estimation and classification estimating and bounding the probability of error classification of stationary time series context-dependent methods other methods of classification.

Some Aspects of Vortex Structure Related to Tropical Cyclone Motion

Abstract: Some effect of tropical cyclone structure on the vortex motion are examined in a nondivergent, barotropic numerical model with no basic current. As suggested earlier by DeMaria, the initial maximum wind speed has little effect on the track. Vortex translation associated with the beta effect depends sensitively on the strength of the flow between 300 and 1000 km from the center. If the flow in this annulus is made more cyclonic, the track will turn cyclonically and move more toward the west in the Northern Hemisphere. The dynamics of this beta-drift is studied via a decomposition into symmetric and asymmetric circulations. The symmetric flow experiences a slight weakening of the maximum wind speed and an anticyclonic circulation is induced beyond 600 km. The asymmetric circulation is dominated by an azimuthal wavenumber one circulation with an anticyclonic gyre east of the center, a cyclonic gyre to the west and a nearly uniform, broad-scale ventilation flow between the gyres. The vortex translati...

The consistent Shapley value for hyperplane games

Abstract: A new value is defined for n-person hyperplane games, ie, non-sidepayment cooperative games, such that for each coalition, the Pareto optimal set is linear This is a generalization of the Shapley value for side-payment games It is shown that this value is consistent in the sense that the payoff in a given game is related to payoffs in reduced games (obtained by excluding some players) in such a way that corrections demanded by coalitions of a fixed size are cancelled out Moreover, this is the only consistent value which satisfies Pareto optimality (for the grand coalition), symmetry and covariancy with respect to utility changes of scales It can be reached by players who start from an arbitrary Pareto optimal payoff vector and make successive adjustments

The dynamics of software project staffing: a system dynamics based simulation approach

Abstract: The author focuses on the dynamics of software project staffing throughout the software-development lifecycle. The research vehicle is a comprehensive system-dynamics model of the software-development process. A detailed discussion of the model's structure as well as its behavior is provided. The results of a case study in which the model is used to simulate the staffing practices of an actual software project are then presented. The experiment produces some interesting insights into the policies (both explicit and implicit) for managing the human resource, and their impact on project behavior. The decision-support capability of the model to answer what-if questions is also demonstrated. In particular, the model is used to test the degree of interchangeability of men and months on the particular software project. >

Software evolution through rapid prototyping

Abstract: Rapid prototyping is defined, and its role in software evolution is examined. Software evolution refers to all activities that change a software system. It differs from maintenance in that the latter is done after the initial development, whereas evolution activities are interleaved with the initial development and continue after the delivery of the initial version of the system. In the author's approach to rapid prototyping, software systems are delivered incrementally and requirements analysis continues throughout the process, interleaved with implementation and evolution. The focus is on reducing requirements errors through prototyping before undertaking the incremental implementation effort for each deliverable version of the system. The evolution of a hyperthermia system is considered as an example. >

keV particle bombardment of semiconductors: A molecular-dynamics simulation.

Abstract: Molecular-dynamics simulations have been performed for the keV particle bombardment of Si{110} and Si{100} using a many-body potential developed by Tersoff. Energy and angle distributions are presented along with an analysis of the important ejection mechanisms. We have developed a computer logic that only integrates the equations of motion of the atoms that are struck, thus decreasing the computer time by a factor of 3 from a complete molecular-dynamics simulation.

Factors affecting the policy for distributing computing resources

Abstract: This article discusses the findings of an empirical study conducted on 303 organizations. The major purpose of the study was to analyze the relationship between various organizational attributes and the deployment of hardware resources. The salient finding was that the most influential variable is the distribution of decision-making processes in the organization. The more decision making is distributed, the more hardware is distributed. No significant relationships were detected between hardware distribution and any of the following variables: organizational structure, economic sectorial association, and the size of the organization.

Vertical Structure of the Ocean Current Response to a Hurricane

Abstract: During the passage of hurricane Norbert in 1984, the Hurricane Research Division of NOAA conducted a Planetary Boundary Layer Experiment that included the deployment of Airborne eXpendable Current Profilers (AXCP). A total of. 16 AXCPs provided for the fist time high-resolution vertical profiles of currents and temperatures in hurricane wind conditions. This study focuses on the vertical structure of the near-inertial baroclinic current excited by the passage of this hurricane. The transient hurricane-induced currents are isolated from the AXCP profiles in Norbert by subtracting a spatially-averaged current. Near the center of hurricane Norbert, the WKBJ-scaled vertical wavenumber spectra are a decade greater than the Garrett-Munk spectra (GM75). The fist ten linear, baroclinic free modes are calculated from the spatially-averaged Brunt–Vaisala frequency. To allow a more direct comparison with the AXCP observations in the current wind regime, the near-inertial response for the three dimensional v...

Barotropic Vortex Stability to Perturbations from Axisymmetry

Abstract: Tropical cyclones and dynamically similar model vortices robustly maintain a near-axisymmetric horizontal structure where the vortex flow is strongly nonlinear in spite of persistent asymmetric forcing represented by horizontal variations in the environmental winds and the Coriolis parameter. Since tropical cyclone motion relative to environmental “steering” has been associated with vortex asymmetries in even the simplest numerical models, identification of a barotropic mechanism that stabilizes vortices to dispersive influences is important. A nondivergent, barotropic analytical model is used to identify the asymmetry-damping influence of symmetric angular windshear as the mechanism by which a barotropic vortex resists asymmetric forcing. Solutions are obtained for the evolution of linear asymmetric perturbations imposed as initial conditions on a steady, Rankine vortical flow. Perturbations combining various radial and azimuthal structures that might be expected from environmental and convectiv...

Estimating the Reliability of Systems Subject to Imperfect Repair

Abstract: This study of statistical inference for repairable systems focuses on the development of estimation procedures for the life distribution F of a new system based on data on system lifetimes between consecutive repairs The Brown—Proschan imperfect-repair model postulates that at failure the system is repaired to a condition as good as new with probability p, and is otherwise repaired to the condition just prior to failure In treating issues of statistical inference for this model, the article first points out the lack of identifiability of the pair (p, F) as an index of the distribution of interfailure times T 1, T 2, … It is then shown that data pairs (Ti, Zi ) (i = 1, 2, …) render the parameter pair (p, F) identifiable, where Zi is a Bernoulli variable that records the mode of repair (perfect or imperfect) following the ith failure Under the assumption that data of the form {(Ti, Zi )} are drawn via inverse sampling until the occurrence of the mth perfect repair, the problem of estimating the

Optimal location of candidates in ideological space

Abstract: The strong point is the point which minimizes the probability that a candidate be defeated in a two-party election. The center of power is the weighted average of voters' positions in a spatial voting game, where the weights are given by Shapley's modified value. We show that, under very general conditions, the strong point and the center of power coincide.

Round Robin computer simulation of ejection probability in sputtering

Abstract: We have studied the ejection of a copper atom through a planar copper surface as a function of recoil velocity and depth of origin. Results were obtained from six molecular dynamics codes, four binary collision lattice simulation codes, and eight Monte Carlo codes. Most results were found with a Born-Mayer interaction potential between the atoms with Gibson 2 parameters and a planar surface barrier, but variations on this standard were allowed for, as well as differences in the adopted cutoff radius for the interaction potential, electronic stopping, and target temperature. Large differences were found between the predictions of the various codes, but the cause of these differences could be determined in most cases. A fairly clear picture emerges from all three types of codes for the depth range and the angular range for ejection at energies relevant to sputter ejection, although a quantitative discussion would have to include an analysis of replacement collision events which has been left out here.

The Use of Information from and about Competitors in Small Business Management

Abstract: Interviews of small business owner/managers were conducted to determine the extent to which they use information from competitors and about competitors. A combination of quantitative and qualitative information indicated that small business managers used competitors less frequently than customers and suppliers as sources of information. In addition, the managers did not analyze the competitors’ products or services closely, and they did not enter into formal arrangements with them.

Miniature five-hole pressure probe for measurement of three mean velocity components in low-speed flows

Abstract: A miniature five-hole pressure probe is described which has a probe tip diameter of 122 mm The probe was developed to measure three mean velocity components using a non-nulling procedure at individual locations in a curved channel where differential pressures are low, flow is three-dimensional and laminar, and spatial resolution and flow blockage effects are important considerations Calibration coefficients are presented for Reynolds numbers based on probe tip diameter ranging from 80 to 400 Coefficients for yaw angle, pitch angle, total pressure and total minus static pressure are independent of Reynolds number within experimental uncertainties Experimental details unique to the use of the miniature probe are also given along with distributions of mean velocity and mean vorticity over a portion of the 127 mm*5080 mm cross section of a curved channel At a Dean number of 119 (mean streamwise velocity approximately 12 m s-1), structural characteristics of Dean vortices are evident from contours of the streamwise velocity, the total pressure and the streamwise component of mean vorticity determined from secondary flow vectors

Ocean Radar Backscatter Relationship with Near-Surface Winds: A Case Study during FASINEX

Abstract: A case study of the ocean radar backscatter dependence on near-surface wind and wind stress is presented using the data obtained on February 18, 1986 during the Frontal Air-Sea Interaction Experiment. The particular wind-wave conditions and their variations across a sharp sea surface temperature front are described. The small change in wind speed across the front cannot account for the large change in wind stress implying significant changes in the drag coefficient and surface roughness length. The results strengthen the hypothesis that radar backscatter is closely correlated to wind stress, and therefore, could be used for remote sensing of the wind stress itself over the global oceans.

Measurements in Vertical Plane Turbulent Plumes

Abstract: Mean-flow and turbulence measurements have been obtained in two-dimensional vertical turbulent plumes in a nominally still ambient. The plumes were generated by injecting hot water vertically upwards from the bottom of a reservior containing cold water. A two-component Laser Doppler Anemometer (LDA) and a “cold-film” resistance thermometer were used to obtain instantaneous velocity and temperature measurements in the plume. The present mean-flow measurements have confirmed many of the earlier measurements on plane plumes, but have also indicated some important differences. The use of the two-component LDA made it possible to obtain data on turbulent intensities, turbulent fluxes and other details of the structure of turbulence in plane plumes. The turbulence measurements have shown that the eddy viscosity and turbulence are significantly higher in the plume compared to an isothermal jet. Detailed measurements of energy balance suggest that buoyant production contributes substantially to this increase.

Bremsstrahlung radiation effects in rare earth permanent magnets

Abstract: Advances in rare earth permanent magnet (REPM) technology have made possible new applications. Two such applications are the use of permanent magnetic lenses for accelerator and beam transport systems and the expanding use in undulators and wigglers of synchrotron radiation and free electron laser systems. Both applications involve potential exposure of REPM's to high radiation fields. We have investigated the radiation hardness of several different varieties of REPM's up to 2 gigarads of absorbed dose from a mixed electron-photon (bremsstrahlung) field. Sm/sub 2/Co/sub 17/, Nd/sub 2/Fe/sub 14/B and an experimental REPM, Pr/sub 15/Fe/sub 79/B/sub 6/, from several different manufacturers have been investigated. Of the samples irradiated, Sm/sub 2/Co/sub 17/ proved to be the most resistant to bremsstrahlung radiation. However, details of manufacturing techniques produced significantly different results. We observed that REPM's of nominally identical stoichiometric composition from different manufacturers did not show the same rate of remanence loss. We present details of our experiment and absorbed dose modeling and a summary of radiation effects measurements of which we are aware. Our study of these radiation damage experiments lead us to the empirical observation that the order of radiation hardness is Sm/sub 2/Co/sub 17/, SmCo/sub 5/ and Nd/sub 2/Fe/sub 14/B, regardlessmore » of the source of radiation, i.e., gammas, electrons, protons or neutrons. 8 refs., 2 figs., 4 tabs.« less

An accurate moment method model for the tapered slot antenna

Abstract: A moment-method model is presented for the radiation characteristics of the tapered slot antenna. It overcomes the shortcoming of an earlier theory. The method is rigorous for the air dielectric antennas. For dielectric-supported antennas, the method is approximate but accurate. The method is particularly accurate for antennas etched on substrates that are electrically thin or have a low dielectric constant, within the limits of ( epsilon /sub r/-1)d/ lambda /sub 0/ >

Heterogeneous databases: proliferations, issues, and solutions

Abstract: The authors characterize the notion of heterogeneous databases as the inevitable consequence of replacing the traditional data processing practice with modern database management. They articulate the current problems and future issues connected with the great proliferation and overwhelming use of heterogeneous databases and their DBMS (database management systems). They survey available DBMS solutions to these problems and issues. The limitations and advantages of various DBMS solutions are examined. To this end, a taxonomy of DBMS solutions to the problems and issues of heterogeneous databases is presented. Some of the current research and proposals on the heterogeneous-database solutions are discussed in the context of the taxonomy. >

Translation and execution of distributed Ada programs: Is it still Ada?

Abstract: Some of the fundamental issues and tradeoffs involved in the translation and execution of programs written in the Ada language and intended for distributed execution are examined. The memory access architecture, binding time and degree of system homogeneity are the three basic characteristics in terms of which target systems can be described. Library subprograms and library packages are identified as natural distributable units of the language. The program-to-process/memory mapping and the unit of the language to be distributed are the key issues in the distribution of Ada. The implications of various alternatives for these are analyzed. >

Spatial resolution and downwash velocity corrections for multiple-hole pressure probes in complex flows

Abstract: Correction schemes for finite spatial resolution and induced downwash velocity are presented which have application to the measurement of complex three-dimensional flow fields using five-hole angle-type pressure probes. In the study, induced downwash velocity is assumed to be proportional to the transverse gradients of streamwise velocity. The present correction schemes are validated by application to flows including vortices embedded within turbulent boundary layers and flows in a curved channel with 1.27-cm width, a 40-to-1 aspect ratio, and 59.7 cm of convex surface curvature.

Horizontal Distribution and Characteristics of Shear Layers in the Seasonal Thermocline

Abstract: High-resolution velocity shear, CTD, and microstructure measurements were made simultaneously from the research submarine Dolphin in Monterey Bay in October 1984. During three consecutive dives, the Dolphin cycled between the surface and 110 m along predetermined tracks 10 miles northwest of Monterey. Inside the seasonal thermocline, the vertical velocity shear appeared to be concentrated in layers 10 m thick extending several kilometers horizontally. The thickness of the shear layers is consistent with the typical size of turbulent patches encountered in the seasonal thermocline. In contrast, no large shear layers were observed below a 50 m depth. The depth levels at which the shear layers were observed were nearly constant throughout each dive, suggesting that the shear layers, with some unknown degree of intermittency, might extend horizontally over several square kilometers. The shear vector inside the seasonal themocline (at σt = 25.5) rotated 360° over an inertial period, but did appear to ...