Showing papers by "Naval Surface Warfare Center published in 2003"
TL;DR: The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer (FRP) composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of these materials by structural designers and civil engineers as discussed by the authors.
Abstract: The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer (FRP) composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of these materials by structural designers and civil engineers. This concern is emphasized since the structures of interest are primarily load bearing and are expected to remain in service over extended periods of time without significant inspection or maintenance. This paper presents a synopsis of a gap analysis study undertaken under the aegis of the Civil Engineering Research Foundation and the Federal Highway Administration to identify and prioritize critical gaps in durability data. The study focuses on the use of FRP in internal reinforcement, external strengthening, seismic retrofit, bridge decks, structural profiles, and panels. Environments of interest are moisture/solution, alkalinity, creep/relaxation, fatigue, fire, thermal effects (including free...
411 citations
TL;DR: In this paper, microstructural evolution during thermal annealing of a cryogenically ball milled Al-7.6 at% Mg alloy with a grain size of ~25 nm was examined using differential scanning calorimetry, x-ray diffraction, and transmission electron microscopy.
224 citations
TL;DR: In this article, the structural transitions associated with different cooling rates from the high temperature disordered state were investigated with X-ray diffraction of oriented single crystals of Fe-19 at% Ga.
218 citations
TL;DR: In this article, self-assembled monolayers (SAMs) are used to passivate unpassivated Al nanoparticles using a perfluoroalkyl carboxylic acid.
Abstract: Surface passivation of unpassivated Al nanoparticles has been realized using self-assembled monolayers (SAMs). Nanoscale Al particles were prepared in solution by catalytic decomposition of H3Al·NMe3 or H3Al·N(Me)Pyr by Ti(OiPr)4 and coated in situ using a perfluoroalkyl carboxylic acid SAM. Because the Al particles are prepared using wet chemistry techniques and coated in solution, they are free of oxygen passivation. This SAM coating passivates the aluminum and appears to prevent the oxidation of the particles in air and renders the composite material, to some extent, soluble in polar organic solvents such as diethyl ether. Characterization data including scanning electron microscopy , transmission electron microscopy, thermogravimetric analysis, and attenuated total reflectance-Fourier transform infrared spectroscopy of prepared materials are presented.
218 citations
TL;DR: The data suggest that the presence of an established biofilm likely serves to moderate the release of Cu from field-exposed antifouling coatings both on panels and hull surfaces.
160 citations
TL;DR: A diverse and unstable bacterial population was indicated throughout the 100-day period, with spikes in feed strength causing significant changes in community structure, and the MBR system was able to meet effluent quality parameters approximately 90% of the time.
Abstract: The bacterial population of a graywater treatment system was monitored over the course of 100 days, along with several wastewater biochemical parameters. The graywater treatment system employed an 1,800-liter membrane bioreactor (MBR) to process the waste, with essentially 100% recycling of the biomass. Graywater feed consisting of 10% galley water and 90% laundry water, selected to approximate the graywater composition on board U.S. Navy ships, was collected offsite. Five-day biological oxygen demand (BOD5), oils and greases (O/G), nitrogen, and phosphorus were monitored in the feed and were found to vary greatly day to day. Changes in the bacterial population were monitored by PCR amplification of region 332 to 518 (Escherichia coli numbering) of the 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE) analysis of the resultant PCR products. DGGE analysis indicated a diverse and unstable bacterial population throughout the 100-day period, with spikes in feed strength causing significant changes in community structure. Long-term similarity between the communities was 0 to 25%, depending on the method of analysis. In spite of the unstable bacterial population, the MBR system was able to meet effluent quality parameters approximately 90% of the time.
111 citations
TL;DR: In this article, the tensile electromechanical coupling coefficients of polyurethane electrostriction were investigated by measuring tensile tensors of structurally different materials, such as DOW 2103-80 AE, DOW 80 AE, phase-separated (PS) materials and phase-mixed (PM) materials with a molecular weight of 2000.
Abstract: Polyurethane electrostriction was investigated by measuring the tensile electromechanical coupling coefficients of structurally different materials. True values of the strain coefficients M3311, M3322, and M3333 were obtained for four types of polymer: one commercial polyurethane (DOW 2103-80 AE) and three polyurethanes synthesized at the Naval Surface Warfare Center, including two phase-separated (PS) materials with molecular weights of 1000 and 2000 and one phase-mixed (PM) material with a molecular weight of 2000. Measurements were performed at 2 kHz under a bias field of 4 MV/m at room temperature. Measured values of M3333 ranged from −9.4 × 10−18 to −74.6 × 10−18 m2/V2, with the PM material exhibiting the largest coefficient. The electrostatic interaction (Maxwell stress) did not account for more than 15% of the total electromechanical activity in any of the materials. Furthermore, at the macroscopic level, an empirical relationship was established to predict the values of the electrostrictive coefficients from the dielectric constants and the compliance coefficients of the material. Finally, results indicated that, at the microscopic level, the phenomenon of electrostriction in polyurethanes could be best explained by the presence of charges inside the material (space–charge theory). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 399–404, 2003
88 citations
TL;DR: It is demonstrated that the proposed semiparametric classifier has performance approaching that of the optimal parametric classifiers in cases for which the optimal is available for comparison.
Abstract: based on proximity between training observations. Performance
comparisons are presented on synthetic and real examples versus
k-nearest neighbors, Fisher's linear discriminant and support vector
machines. We demonstrate that the proposed semiparametric classifier has
performance approaching that of the optimal parametric classifier in cases
for which the optimal is available for comparison.
67 citations
TL;DR: A conceptual pulsed-power system for driving ship-based long-range electromagnetic guns based on state-of-the-art power-supply, capacitor, and switching technologies is described.
Abstract: Proposed ship-based long-range electromagnetic guns require input energies greater then 100 MJ, at peak powers in excess of 50 GW, and at average power in the tens of megawatts. This paper describes a conceptual pulsed-power system for driving these types of guns. A generic design was developed based on state-of-the-art power-supply, capacitor, and switching technologies. Results of modeling and parametric studies are presented, and key issues that impact system size and configuration are explored. An assessment is made of the feasibility of integrating this type of system into an electric-drive ship.
64 citations
TL;DR: In this paper, the impedance of a cylindrical coil and a planar circular spiral coil carrying an alternating current above a defect-free conducting magnetic half-space and a conductive magnetic halfspace containing an infinitely long slot with uniform depth and width is examined in detail.
Abstract: The impedance of a cylindrical coil and a planar circular spiral coil carrying an alternating current above (i) a defect-free conducting magnetic half-space and (ii) a conducting magnetic half-space containing an infinitely long slot with uniform depth and width is examined in detail. Closed-form expressions for the coil impedance in these cases are presented, based on the theories of Dodd and Deeds and Harfield and Bowler. The validity of these expressions is tested by measurements using steel plates over the frequency range 100 Hz-10 MHz. The theoretical predictions are in good agreement with experiment, with the best agreement for the smallest slot width. The results confirm that thin, flexible spiral coils offer some attractive features for eddy-current detection of cracks in metals, particularly in terms of sensitivity and potential for unobtrusive permanent attachment to the material being inspected. Approximate expressions for a spiral coil above a defect-free magnetic half-space are also given to allow easy calculation in limiting cases.
63 citations
01 Aug 2003
TL;DR: In this article, the authors address the hit-to-kill missile flight control problem by casting it as an integrated guidance-control problem, which automatically compensates for the impact of the autopilot lag on the miss distance.
Abstract: Due to their potential for reducing the weapon size and efficiency, design methods for realizing hitto-kill capabilities in missile systems are of significant research interest in the missile flight control community. As defined in this paper, hit-tokill capability requires the missile to consistently achieve point-mass miss distances less than half the minimum dimension of the target. It has been noted in the literature that the chief contributors to the miss distance in homing missiles are the seeker errors, autopilot lag, target maneuvers, and target state estimation lag. Guidance laws for ameliorating the effects of each of these miss distance components have been discussed in several recent publications. The present research addresses the hit-to-kill missile flight control problem by casting it as an integrated guidance-control problem. By including the complete dynamics of the missile, the integrated guidance-control formulation automatically compensates for the impact of the autopilot lag on the miss distance. The resulting finite-interval control problem is then solved using a transformation approach. Interception by a kinetic warhead is used as an example to illustrate the performance of the integrated guidance-control law.
TL;DR: In this article, the authors compared different methods of predicting hydrodynamic impacts with available test data of 2-D wedge-shaped section shapes, based on peak pressures at different impact velocities.
TL;DR: In this paper, a prototype in-water laser line-scanning multispectral fluorescence imaging system was evaluated for its ability to provide data that could be used to determine the quantitative distribution and abundance of various functional groups on coral reefs.
Abstract: A prototype in-water laser line-scanning multispectral fluorescence imaging system was evaluated for its ability to provide data that could be used to determine the quantitative distribution and abundance of various functional groups on coral reefs. The system collected fluorescence imagery in three spectral bands with 1 cm 2 resolution at sites in Florida and the Bahamas. Fluorescence excitation was at 488 nm, and imagery was collected in emission bands centered at 520, 580, and 685 nm. Ground truth data on bottom cover was collected by divers using conventional line transect and photographic quadrat methods. A set of classification rules based on the relative signal levels in the three fluorescence channels was developed to assign the image pixels to functional groups. Once the image was classified, percent cover data for the groups were computed for the full image and for subsets of the image chosen to simulate line transect, grid survey, and photographic quadrat surveys. The statistics of percent cover of various bottom types derived from the fluorescence image compared favorably with those determined by diver survey techniques. The results demonstrate that fluorescence imaging has the long-term potential to provide coverage of large spatial areas of coral reefs at high resolution, with automated classification and quantification of functional groups in the image.
TL;DR: In response to several claims from Manufacturers that intumescent coatings could be used in place of fire insulation and provide equal protection to shipboard structures during a fire, U.S. Navy conducted an extensive investigation of several fire protective coatings for use aboard ship as discussed by the authors.
Abstract: In response to several claims from Manufacturers that intumescent coatings could be used in place of fire insulation and provide equal protection to shipboard structures during a fire, U.S. Navy conducted an extensive investigation of several fire protective coatings for use aboard ship. These fire protective coatings included water and solvent based coatings, insulative coatings, and foams. The objective of this program was to identify passive fire protection (PFP) coatings for shipboard interior applications capable of meeting U.S. Navy (USN) fire resistance requirements (DRAFT MIL-PRF-XX 381) of 30 min rating with backside average temperature rise less than 139 C using UL-1709 fire curve (post flashover fire). This evaluation consisted of small scale fire, adhesion, and impact tests; intermediate scale room corner fire tests, and full scale fire tests conducted aboard ex-USS SHADWELL. The test results with steel substrate show that all candidate coatings failed to meet minimum U.S. Navy fire resistance...
TL;DR: In this article, three full-scale fire tests were performed with an area initiating fire in a combustible lined corner with a ceiling, and the mock corner was lined with a different combustible material, plywood and two different composite materials.
01 Jan 2003
TL;DR: In this article, the magnetoelastic transduction properties of single-crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic, and thermal conditions were characterized.
Abstract: The objective of this work is to characterize the magnetoelastic transduction properties of single-crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic, and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties are significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single-crystal response to major- loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress are examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded, and single-crystal specimens. The paper concludes with a magnetic characterization summary of the different Fe-Ga alloys examined.
10 Nov 2003
TL;DR: This paper shows that some built-in-test (BIT) systems have an intrinsic 50 percent false alarm rate and shows how Bayes' theorem can be used to analyze how variation of BIT characteristics can increase or decrease the intrinsicfalse alarm rate.
Abstract: This paper shows that some built-in-test (BIT) systems have an intrinsic 50 percent false alarm rate The paper also shows how Bayes' theorem can be used to analyze how variation of BIT characteristics can increase or decrease the intrinsic false alarm rate
TL;DR: In this article, a two-stage light gas gun was used for the expansion and fragmentation of tubes using a limited number of simulations performed with CTH, and the results of experiments on two materials, which provided insight into the physics of the process.
TL;DR: Because it is essentially impossible to store streaming data, recursive algorithms, algorithms which are adaptive and discount the past and also algorithms that create finite pseudo-samples are considered and some evolutionary graphics procedures that are suitable for streaming data are suggested.
Abstract: We consider the implications of streaming data for data analysis and data mining. Streaming data are becoming widely available from a variety of sources. In our case we consider the implications arising from Internet traffic data. By implication, streaming data are unlikely to be time homogeneous so that standard statistical and data mining procedures do not necessarily apply. Because it is essentially impossible to store streaming data, we consider recursive algorithms, algorithms which are adaptive and discount the past and also algorithms that create finite pseudo-samples. We also suggest some evolutionary graphics procedures that are suitable for streaming data. We begin our discussion with a discussion of Internet traffic in order to give the reader some sense of the time and data scale and visual resolution needed for such problems.
TL;DR: A new finite volume method for the incompressible Navier–Stokes equations, expressed in arbitrary Lagrangian–Eulerian (ALE) form, is presented, using a staggered storage arrangement for the pressure and velocity variables and adopting an edge‐based data structure and assembly procedure which is valid for arbitrary n‐sided polygonal meshes.
Abstract: A new finite volume method for the incompressible Navier–Stokes equations, expressed in arbitrary Lagrangian–Eulerian (ALE) form, is presented. The method uses a staggered storage arrangement for the pressure and velocity variables and adopts an edge-based data structure and assembly procedure which is valid for arbitrary n-sided polygonal meshes. Edge formulas are presented for assembling the ALE form of the momentum and pressure equations. An implicit multi-stage time integrator is constructed that is geometrically conservative to the precision of the arithmetic used in the computation. The method is shown to be second-order-accurate in time and space for general time-dependent polygonal meshes. The method is first evaluated using several well-known unsteady incompressible Navier–Stokes problems before being applied to a periodically forced aeroelastic problem and a transient free surface problem. Published in 2003 by John Wiley & Sons, Ltd.
TL;DR: An exploratory data analysis methodology for characterizing the scale dimension of a classi#cation problem to characterize the support of one distinguished target class as a collection of balls covering the class, with each ball centered at an observation in that class such that the radius is maximal without containing observations from the other classes.
TL;DR: A data visualization technique for class cover catch digraphs which allows for the discovery of latent subclasses representing chemical concentration in the artificial nose data and two subtypes of acute lymphoblastic leukemia in the gene expression data and the associated conjectures pertaining to the geometry of these subclasses in their respective high-dimensional observation spaces are introduced.
TL;DR: In this paper, an average-value model is developed for the four-level diode-clamped converter which takes into account the active capacitor voltage balancing control, and the model performance prediction is compared to a detailed model and laboratory measurements on an 18 kW rectifier/inverter test system.
Abstract: Multilevel power converters have gained much attention in recent years due to their high power quality, low switching losses, and high-voltage capability. These advantages make the multilevel converter a candidate for the next generation of naval ship prolusion systems. Evaluation of these systems is typically assisted with a dynamic average-value models in order to rapidly predict system performance under several operating scenarios. In this paper, an average-value model is developed for the four-level diode-clamped converter which takes into account the active capacitor voltage balancing control. This model performance prediction is compared to a detailed model and laboratory measurements on an 18 kW rectifier/inverter test system.
04 Jun 2003
TL;DR: A new guidance law termed generalized vector explicit guidance (GENEX) has the ability to simultaneously achieve design specifications on miss distance and final missile-target relative orientation and may be used to enhance the performance of warheads whose effectiveness is influenced by the terminal encounter geometry.
Abstract: This paper evaluates a new guidance law termed generalized vector explicit guidance (GENEX). This guidance law has the ability to simultaneously achieve design specifications on miss distance and final missile-target relative orientation. The latter specification may be used to enhance the performance of warheads whose effectiveness is influenced by the terminal encounter geometry. The GENEX guidance law is parameterized in terms of a design coefficient n which is specified by the user and which determines the degree of curvature (and hence control usage) in the trajectory. Feasibility of the GENEX guidance law was demonstrated by its application to a missile terminal homing scenario. Under conditions of ideal sensor information, and assuming a simplified single-lag missile response model, the guidance was shown to perform well against an air target performing evasive maneuvers. The specified zero aspect terminal encounter angle was achieved while simultaneously minimizing the miss distance.
TL;DR: In this article, a fire growth model was developed to predict the flame spread and total heat release rate of a fire in a corner configuration with a combustible lining using small-scale test data from the ASTM E1354 cone calorimeter and ASTM LIFT.
TL;DR: In this paper, the authors measured the stress-strain hysteresis losses of Tb/sub x/Dy/sub 1-x/Fe/sub sub 1.92/(x=0.30, 0.33,0.40, and 0.50) at a variety of magnetic fields between 0 and 1600 Oe.
Abstract: The stress-strain hysteresis losses of Tb/sub x/Dy/sub 1-x/Fe/sub 1.92/(x=0.30, 0.33, 0.40, 0.45, and 0.50) were measured at a variety of magnetic fields between 0 and 1600 Oe. Stress ranges from /spl sim/0 to -10, -20, -40, and -60 MPa (the minus sign indicates compressive stresses) were used. The hysteresis loop area increased from 5.7 kJ/m/sup 3/ at x=0.30 to 10 kJ/m/sup 3/ at x=0.50 as the Tb concentration and the magnetic anisotropy increased. The position of the hysteresis loop shifted to larger compressive stresses as the magnetic field was increased allowing the strength of the damping to be controlled by the magnetic field.
TL;DR: In this paper, the evolution of the oxidation state and atomic structure of V in nanophase V 2 O 5 aerogel and ambigel cathodes under in situ conditions using X-ray absorption spectroscopy (XAS).
Abstract: We examined the evolution of the oxidation state and atomic structure of V in nanophase V 2 O 5 aerogel and ambigel cathodes under in situ conditions using X-ray absorption spectroscopy (XAS). We show that the oxidation state of V in V 2 O 5 aerogel and ambigel cathodes heated under vacuum (100 μ Torr) at 220°C for 16 h is similar to that of V in a commercially obtained sample of orthorhombic V 2 O 5 . However, the local structure of V in aerogel and ambigel V 2 O 5 has a higher degree of local symmetry relative to orthorhombic V 2 O 5 and/or the average V-O bond length is greater than that of orthorhombic V 2 O 5 . Furthermore, we show that during the first cycle of discharge, the degree of Li insertion (x in Li x V 2 O 5 ) for the ambigel cathode is greater than that of the aerogel cathode (x = 3.06 for the ambigel cathode compared to x=2.68 for the aerogel cathode) for the same cut-off voltage. Accordingly, the observed V K-edge energy shift for the fully discharged ambigel cathode is greater than that observed for the fully discharged aerogel cathode, and hence, the extent of reduction of pentavalent V is greater for the ambigel cathode. In both cases, the extent of reduction of the V is consistent with the amount of Li inserted (i. e., Li x V 2 O 5 ). Initially, pentavalent V is reduced to tetravalent V in the intercalation range 0 2). Analyses of Fourier transform data reveal that V has a higher degree of local symmetry in the discharged state relative to that of the charged state.
TL;DR: In this article, the authors compared different control methods developed for the alternate control task of tracking an axial dynamic target, based on fuzzy logic, sliding mode, and direct linearization.
15 Apr 2003
01 Jan 2003
TL;DR: In this article, film cooling performance on a simulated turbine vane model with an objective of determining how much the coolant density ratio affects this performance was studied on a simulator with the purpose of determining if tests done at small density ratios (often more viable in a laboratory) can give reasonable predictions of performance at more realistic large density ratios.
Abstract: Film cooling performance was studied on a simulated turbine vane model with an objective of determining how much the coolant density ratio affects this performance. Experiments were conducted using coolant density ratios of 1.8 and 1.2. The purpose of the study was to determine if tests done at small density ratios (which is often more viable in a laboratory) can give reasonable predictions of performance at more realistic large density ratios. Furthermore, appropriate scaling parameters were determined. The mainstream flow was operated with low and high turbulence levels. Adiabatic effectiveness was measured in the showerhead region of the vane, and following the first row of coolant holes on the pressure side. Adiabatic effectiveness performance using small density ratio coolant gave performance trends similar to the large density ratio coolant, but quantitative values differed by varying amount depending on operating conditions.Copyright © 2003 by ASME