bluuebunny/crossref_metadata_2025 huggingface dataset:
Estuarine Invertebrates and Fish: Sampling Design and Constraints for Long-Term Measurements of Population Dynamics
Authors: Hines AH , Haddon PJ , Miklas JJ , Wiechert LA , Haddon AM
Published: December 2008

The first five to six years of a long-term data set are presented for invertebrates and fish representing an array of physiological tolerances, trophic levels, and life history strategies in a lower mesohaline subestuary of Chesapeake Bay. Population abundances were estimated for infaunal invertebrates with cores taken four to six times per year at five stations, for nearshore fish with seines taken once per year at 14 stations, and for epibenthic fish and crabs taken in trawls eight times per year at three stations. Physical/chemical parameters of estuarine water were monitored continuously. Analyses of variance and covariance were used to account for variation associated with seasonal cycles and to test for effects of year, station, and salinity on population abundances.

A 16-year record of meteorological and water parameters showed that the study period spanned a multiyear period of regional drought in the 1980s, which resulted in markedly increased salinities and reflected a greater deviation from the long-term average than reduced salinities during major storms of the 1970s. ANOVA and ANCOVA models accounted for 12 to 82% of the variation in population abundance, depending on the species. All but two species showed significant differences in population abundances among years in six years' data for 19 infaunal invertebrate species, six years for 18 species of nearshore fish, and five years for five species of epibenthic fish and crabs. Most species exhibited severalfold differences in abundance among years. About half of the infaunal species, several of the nearshore fish, and four epibenthic species showed significant responses to elevated salinities. However, despite the overall importance of salinity on estuarine systems, only a small fraction (1 to 6%) of the variation in any one species was explained by salinity changes. Failure to account for more of the population variation by salinity resulted from: (1) the significant spatial (station) variation and the significant interaction of time and spatial variation in nearly all species; (2) the importance of other meteorological and water quality parameters in regulating populations; (3) salinity being important primarily during a critical period (for example, during spring recruitment) because other factors (for example, predation) may override the controlling influence of salinity during the other seasons; (4) the spatial scale of the study area being too small too exhibit major shifts in species abundance across the major salinity zones of the estuarine gradient; (5) the location of the study area at the low end of the mesohaline zones means that high salinities dominating the study period are unlikely to affect euryhaline species as much as low salinities; and (6) possible biases of short-term variation since most years of the study perios were characterized by unusually high salinity.
Development, Management, and Analysis of a Long-Term Ecological Research Information Base: Example for Marine Macrobenthos
Authors: Michener WK , Feller RJ , Edwards DG
Published: December 2008

As one of eleven Long-Term Ecological Research Program sites in the nation (designated by the National Science Foundation), the Belle W. Baruch Institute for Marine Biology and Coastal Research has developed a flexible system for the management and analysis of ecological data. The Baruch Data Management System (BDMS) contains over four years of data collected from ecological research on coastal and estuarine habitats. Important design features of information bases for long-term monitoring are described.

Since temporal variability is an inherent part of ecological data sets, it is important to delineate those periods when sampling must be intensified and periods when sampling can be decreased without compromising documentation of the processes under question. Examples of analyses of temporal variability for one of the biological data sets (macrobenthos) are presented, and a case is made for the importance of long-term monitoring efforts to the generation of process-related experiments.
The Use of Modern Atomic Spectroscopy in Industrial Analysis
Authors: Savolainen A , Griffin H , Olear G
Published: December 2008

Industrial laboratories are being forced to develop faster, more accurate and precise but less expensive analytical methods. This paper describes one laboratory's learning process over the past 20 years. The changes that occurred by changing from wet chemistry and arc/spark emission spectroscopy to atomic absorption spectrometry to manual and then automated plasma spectroscopy are described. The rationale of choosing a particular plasma spectrometer is explained along with how to automate specimen introduction, computerize data collection, and display results of a running analysis. An algorithm used to improve results is also described.

A number of different methods that were developed for the new methodology are described. These methods cover a wide range of topics such as plating bath analysis, steel analysis, precious metals analysis, comparisons to fire assaying, analysis of impurities in titanium dioxide (TiO2), and solders. Along with these methods are some time studies that demonstrate the economic rational for buying this type of instrumentation.
Microprocessor-Based Determinator Design and the Impact of Future Trends in the Area of Computer-Controlled Automation of Analytical Chemistry Methods
Authors: Fricioni RB
Published: December 2008

The design of analytical instrumentation has always made use of the latest electronic technology to provide the fastest and most accurate methods for analysis. The present and the future is no different than the past. Computer and microprocessor technology offers solutions to analytical problems that until this period of time had to be lived with.

Designers, while holding on to basic analytical techniques, cannot incorporate corrections for previously known but uncontrollable factors. Computer and microprocessor based design offers the designer the capability of automating manual analytical methods that previously were simply too complex. The design of such systems follows the same exacting evaluation process as used in the past. Evaluations for the most efficient extraction, isolation or separation, detection, signal process, and systems control methods are made and compiled to result in a fast, accurate, and easy to use system.

The combination of electronics, electro-mechanics, and analytical methods is continuing with the advent and development of robotics. Combined with the technology of todays instrumentation robotics can offer further productivity and efficiency of the analytical lab.
Analytical Laboratory Information Management System (ALIMS)
Authors: Blair FA , Arritt JM , Lundy LJ
Published: December 2008

A computerized system has been developed that closely approaches total laboratory data automation. The system is menu driven, permitting the analyst to easily step through a hierarchy of works instructions. Data generation, calculations, dissemination, and retention are fully automated for instruments and automated for wet-chemical analyses prior and subsequent to raw data collection.

The system begins with the log-in of samples for which unique identification numbers are automatically generated. The total routine workload can then be scheduled by the computer. Overrides permit appropriate variations. Work centers query the system for assignments. The system not only controls and monitors work flow but invokes analytical and quality control procedures as well. For management control, sample status is readily available.

Instruments controlled by the system include inductively coupled plasma, atomic absorption spectrophotometer, optical emission spectrophotometer (ICP, AAS, OES), analytical balances, LECO analyzers, ultraviolet-visible spectrophotometer (UV-VIS), and automatic titrators. Report capability exists for back-logs, sample status, quality control, cost accounting, and periodic performance.
Optical Properties of Infrared Transmitting Glasses
Authors: Mitra SS
Published: December 2008

Considerable interest has recently been evidenced in infrared transmitting glasses for components such as laser windows, IR domes and IR optical fibers. In particular, multicomponent heavy metal fluoride glasses based on zirconium or hafnium have displayed desirable optical characteristics, viz., low refractive index, absorption and scattering losses, and a very wide spectral transparent regime, in addition to attractive mechanical and chemical properties.

This talk will review the optical properties of this and related metal halide glasses over the entire spectral range (9 μm to 260 nm). This will include review of experimental data for the ultraviolet absorption edge, infrared edge absorption and temperature dependence, and the understanding of the latter through fundamental vibrational spectra, information regarding which is obtained from a study of infrared reflection and Raman scattering measurements. Effects of nuclear radiation on the optical properties of a number of these glasses will be presented.
Strehl Ratio Measurements of Laser Damaged Plastics
Authors: Mullins BW , Richert BA
Published: December 2008

Plexiglass G, manufactured by Rohm Haas, was irradiated by 10 nsec pulses from a Nd-YAG laser ranging in energy from 0.80 to 1.01 mJ/pulse. Aligned colinearly with the Nd-YAG pulse was a cw HeNe laser beam that measured changes in the transmission characteristics of the plastics. These transmission measurements enabled the Strehl Ratio, S, of the laser induced damage site to be calculated. When S < 0.995 there is a 92% probability of causing permanent damage. Conversely, when S > 0.995 there is a 94% chance of not causing permanent damage to the plastic. These probabilities were independent of laser pulse energies. Evaluation of the resulting diffraction patterns from the permanent damage sites indicates an ∼ 20μm diameter of the optical scattering center in the plastic. These damage sites cause an rms wavefront distortion ranging from 0.009λ to 0.0301λ at the HeNe wavelength.
Laser Induced Bulk Damage in SiO2 at 1.064, 0.532 and 0.355 μm
Authors: Merkle LD , Koumvakalis N , Bass M
Published: December 2008

In this paper we present bulk damage measurements of crystalline quartz and fused silica under single and multiple pulse irradiation where the wavelength was extended to 0.355 μm. In previous work under irradiation at 1.06 and 0.532 μm, it was shown that whereas the single pulse damage varies little with material or wavelength, the multiple pulse damage depended strongly on both. Also, in the case of multiple pulse damage the distribution of the number of pulses needed to produce damage as a function of intensity is indicative of an accumulation process.

If the present work at 0.355 μm the multiple and single pulse damage dependence on focal spot-size, pulse duration and pulse repetition frequency is examined, it is found that the multiple pulse damage shows a much stronger dependence on material, spot-size, pulse duration and wavelength than does the single pulse damage. In addition, more pulses are needed to produce macroscopic damage at a given intensity under irradiation at a 1 Hz pulse repetition rate than at 10 Hz. Possible mechanisms of the repetition rate dependence are briefly discussed.
Optical Properties of Diamond-Machined Metal Surfaces and Their Relationship to Physical and Chemical Surface Perfection
Authors: Decker DL , Hurt HH , Porteus JO , Grandjean DJ
Published: December 2008

It has been demonstrated that copper and other metal surfaces can be diamond single-point machined (DSPM) to a surface quality which will result in nearly intrinsic optical properties. Especially interesting is the observation of the interrelationship of laser-induced melt and slip thresholds for DSPM copper for different surface preparation methods. Particularly important parameters are the machining fluid and the tool geometry. Both of these factors influence the degree of cold work introduced into the surface. In a companion paper at this conference, the nature of the surface damage is correlated with machining conditions. In this paper, the same surfaces are described optically. Significant variation in optical and mechanical properties can be demonstrated. The ability to change the characteristics including laser damage properties of the machined surface can be used in some cases to advantage, to actually tailor the surface to the requirements of a specific application.
Thermally Induced Effects on the Infrared Reflectance of Metal Mirrors
Authors: Hodgkin VA , Decker DL , Hurt HH
Published: December 2008

The experimentally measured infrared (IR) reflectance of metals has sometimes been known to depart significantly from that predicted by simple theory. This departure is a complex function of the bulk and surface properties, method of fabrication, age, and temperature history of the metal. This paper presents data which show the effects of the thermal history of a metal on its IR reflectance as a function of these parameters. The overall sample set consisted of copper (bulk and thin film), aluminum (thin film and bulk alloy), silver (thin film), and molybdenum (bulk) mirrors, and each metal was further categorized as to age, fabrication, and if a thin film by substrate. Reflectance measurements at wave-lengths between 9.72 and 0.8 μm, inclusive, were then made for each category in air at room temperature prior to and following a thermal excursion to look for resulting effects. In addition, each category contained a control sample in order to filter out changes due entirely to age and storage, and a “standard” was periodically measured to track any instrumental drifts occurring with time. The data presented herein represent only one thermal excursion, and yet the data show that just one cycle can have complex effects upon the IR reflectance of a metal, depending upon the temperature of the excursion and how and when the mirror was made.
Single-shot, Cummulative and PRF Dependent Laser Induced Damage Thresholds
Authors: Wood RM , Waite P , Sharma SK
Published: December 2008

During the course of several laser damage programmes at HRC evidence has been accumulated on the different mechanisms and morphology of damage. This evidence has been gained at both 1.06 and 10.6 μm during single-shot, cummulative and prf testing of laser components.

This paper discusses, with both quantitative and photographic data the significance of (1) variation of the damage threshold values gained as a function of laser spot size and laser beam power and energy characteristics, and (2) the size and morphology of the damage spot gained under single shot, multiple and cummulative irradiation at prf's up to 100 Hz. Results are presented on Ge, ZnSe, ZnS, GaAs, CdTe, NaCl, KCl substrates and coated components at 10.6 μm and PMMA, fused silicon, Nd:laser glass and coated components at 1.06 μm.
Light Scattering from Surfaces with Microroughness and Static Density Variations in the Bulk Dielectric Permittivity
Authors: Elson JM
Published: December 2008

First-order perturbation theory is used to calculate the scattering of a plane wave from the surface of a semi-infinite medium, where the surface is slightly rough and the scattering medium is isotropic but has a dielectric permittivity which varies as a function of position. Both the roughness and dielectric permittivity perturbations, which are treated as random variables, can independently cause scattering, and there is generally interference between the two scattered fields. The scattering depends on the autocovariance functions for the surface roughness and dielectric fluctuations and their cross-correlation properties. Thus, the polarization ratio between the p and s angle resolved scattering components is found to be a variable that depends on the autocovariance functions of, and cross-correlation between, the surface roughness and dielectric fluctuations. This result is unlike predicted scattering caused by roughness or dielectric perturbations alone; in these cases, the polarization ratios do not depend on the statistical properties of the perturbation. Numerical results of the calculations of this work are consistent with some aspects of experimental measurements. In particular, measurements of the polarization ratio of light retroscattered from apparently identical silver films are seen to vary widely between samples and even from place to place on the same sample. The present work shows one physical mechanism as to how this can occur.
1.06 Micron Laser Damage of Thin Film Optical Coatings — a Round Robin Experiment Involving Various Pulse Lengths and Beam Diameters
Authors: Guenther KH , Humpherys TW , Balmer J , Bettis JR , Casparis E , Ebert J , Eichner M , Guenther AH , Kiesel E , Kuehnel R , Milam D , Ryseck W , Seitel SC , Stewart A , Weber H , Weber HP , Wirtenson G , Wood RM
Published: December 2008

A number of commercially available optical coatings, both antireflective and high reflective, have been tested for their laser induced damage threshold, involving a total of eight (8) different laboratories. The results obtained and the experimental methods used at these laboratories were discussed among the participants in this round robin at a minisymposium held at Balzers, Liechtenstein, December 9–10, 1982. A final report of the round robin and a summary of the conclusions drawn at that symposium are presented.
Measurements of the Dependence of Damage Thresholds on Laser Wavelength, Pulse Duration and Film Thickness
Authors: Rainer F , Vercimak CL , Milam D , Carniglia CK , Hart TT
Published: December 2008

Results of three experiments will be described. We used 351-nm and 355-nm pulses with durations of 0.6, 1, 5 and 9 ns to measure thresholds for a variety of anti-reflectance and high reflectance coatings. The functional form tm, with t the pulse duration, was used to scale fluence thresholds measured at 0.6 ns to those measured at 9.0 ns. Values of the coefficient m ranged from 0.10 to 0.51. The average value was 0.30. In the second experiment, we measured thresholds at 1064 nm, 527 nm and 355 nm for single-frequency high reflectance ZrO2/SiO2 coatings. Coatings for all three frequencies were deposited simultaneously by use of masks in the coating chamber. Thresholds varied from 2–4 J/cm2 at 355 nm to 7–10 J/cm2 at 1064 nm. The third experiment measured thresholds at 355 nm for antireflection coatings made with layer thicknesses varying from greater than one wavelength to less than a quarterwavelength. A significant variation of threshold with coating thickness was not observed, but the median thresholds increased slightly as coating thickness increased.
Phase Shift Variations on HEL Mirrors
Authors: Leonard TA , Loomis JS
Published: December 2008

An automated IR ellipsometer was used to measure the ellipsometric parameters, ψ and Δ, on multilayer mirrors at 3.80 μm. Spatial variations in differential phase shift, Δ, are modeled by thickness variations in the multilayer coating and variations in ψ are modeled by an absorption change.
Recent Damage Results for Antireflection Coatings at 355 nm
Authors: Hart TT , Carniglia CK , Rainer F , Staggs MC
Published: December 2008

High-index and low-index thin-film antireflection (AR) coatings for use at 355 nm have been tested to determine their resistance to laser damage. All coatings consisted of dielectric materials which were vacuum deposited onto bowl-feed polished Suprasil II by evaporation. Laser damage studies were made by irradiating several sites on each sample with a 0.6 ns, 355 nm laser pulse. Each site was irradiated by only one pulse.

High-index coatings were made with both a high-index material and a low-index material. The high-index materials chosen for this study were scandia (Sc2O3), hafnia (HfO2), and zirconia (ZrO2), while the low-index materials were silica (SiO2) and magnesium fluoride (MgF2). All coatings had four non-quarterwave thick layers plus a halfwave-thick undercoat (barrier layer) of the low-index material. Average damage threshold values for four samples of each type ranged from 2.4 J/sq. cm to 3.1 J/sq. cm. Coatings made from scandia/magnesium fluoride had the highest damage thresholds.

Low-index coatings contained only low-index materials. The low-index materials chosen for this study were samarium fluoride (SmF3), lanthanum fluoride (LaF3) thorium fluoride (ThF4), silica, magnesium fluoride, and lithium fluoride (LiF). AR coatings containing three to six quarterwave-thick layers plus a halfwave-thick barrier layer were made from nine combinations of these six materials. Average damage threshold values for four to six samples of each type ranged from < 1.0 J/sq. cm to 2.8 J/sq. cm. Coatings made from samarium fluoride/magnesium fluoride had the highest damage thresholds.

One set of four scandia/silica coatings was measured at both 355 nm and 248 nm. Damage thresholds at 248 nm for these parts were determined using 20 ns laser pulses. The average threshold was 4.2 J/sq. cm.
Defect Damage Precursors in Visible-Wavelength Mirrors
Authors: Marrs CD , Porteus JO , Palmer JR
Published: December 2008

Video monitoring of pulsed visible-wavelength mirror damage has led to observation of illuminated defects as a precursor to observable microscopic damage. The blue-green illuminating radiation is produced in individual 0.5 μs pulses by a tunable flashlamp-pumped dye laser. The laser light is focused on multilayer dielectric or metal surfaces in an ⋍ 0.5 mm (D − 1/32) spot with a reproducible, flat-top spatial profile. An area slightly larger than the focal spot is viewed with a close-focusing Questar telescope equipped with a highly sensitive video camera. Typically, at nondamaging energy densities, defect sites within the focal spot area appear to be brightly illuminated at the laser wavelength. In dielectric mirrors, the illumination pattern depends on the laser wavelength, suggesting a sensitivity to defect position with respect to the standing wave field. At higher energy densities, laser damage originates only at certain defect sites, while other areas fail to damage even after many laser pulses. This paper presents results of an experimental characterization of the described phenomena.
Predamage Threshold Electron Emission from Insulator and Semiconductor Surfaces
Authors: Siekhaus WJ , Kinney JH , Milam D
Published: December 2008

Predamage electron emission shows a dependence on fluence, bandgap and wavelength consistent with multiphoton excitation across the bandgap and inconsistent with avalanche ionization and thermionic emission models. The electron emission scales with pulselength as τ−1/2.
Laser Induced Damage of a Thin Film With an Absorbing Inclusion: Thermal Considerations of Substrates and Absorption Profiles
Authors: Lange MR , McIver JK , Guenther AH
Published: December 2008

A study of pulsed laser induced damage to thin films is conducted within the context of the impurity-dominated damage model in which the thin film component of the model is emphasized. In this case, a cylindrical impurity is embedded in a single thin film layer between a free surface and a substrate. The effect of the substrate is studied by varying its thermal properties with respect to those of the thin film. The nonuniform distribution of radiation in the film is incorporated into the model by assuming that the absorption is proportional to the standing wave intensity pattern of the field. These results are compared to the results found in previous studies of impurities embedded in infinite mediums.
The Effects of Self-Focusing on Laser-Induced Breakdown
Authors: Williams WE , Soileau MJ , Van Stryland EW
Published: December 2008

The polarization dependence of laser-induced breakdown and beam distortions in the transmitted time integrated spatial profile were used to determine the effects of self focusing on picosecond breakdown threshold measurements in fused silica and NaCl. The results at 1.06 and 0.53 μm laser wavelength indicate that, for focused geometries, no significant self-focusing occurs in these materials until the beam power approaches P2, the second critical power for self-focusing.
Refractive Index of Ternary and Quaternary Compound Semiconductors Below the Funadmental Absorption Edge: Linear and Nonlinear Effects
Authors: Jensen B , Torabi A
Published: December 2008

The index of refraction n is calculated as a function of frequency and mole fraction x for the following compounds: Hg1−xCdxTe, AlxGa1−xAs, and In1−xGaxAsyP1−y lattice matched to InP. Lattice matching of In1−xGaxAsyP1−y to InP requires that x = 0.466 y. The theoretical result for the refractive index is obtained from a quantum mechanical calculation of the dielectric constant of a compound semiconductor. It is given in terms of the basic material parameters of band gap energy, effective electron mass mn, effective heavy hole mass mp, spin orbit splitting energy, lattice constant, and carrier concentration ne or p for n-type or p-type materials, respectively. If these quantities are known as functions of mole fraction x, there are no adjustable parameters involved. A negative change in the refractive index near the fundamental absorption edge is predicted on passing radiation through a crystal if the change in carrier concentration of the initially unoccupied conduction band is assumed proportional to internal intensity I. Comparison of theory with experimental data is given.
Evolution of Steel Protection: A Personal View
Authors: Lopata SL
Published: December 2008

This paper covers 45 years of personal experience in the development of corrosion-resistant protective coatings for steel and concrete and experience in industry practices in corrosion prevention since World War II. The performance of traditional coatings for the protection of steel is outlined, followed by a comparison with various high-performance coatings based on vinyl, epoxy, and ethyl silicate binders. The effect of surface preparation on coating performance is described, together with an indication of the formulation of coatings of superior performance in chemical environments on rusty steel when abrasive blasting is impossible under plant conditions. The paper concludes with a plea for thorough, statistically designed long-term testing of experimental formulations, so as to ensure adequate correlations between laboratory results and plant exposures.
Quantitative Evaluation of Blistering and Corrosion in Organic Coating Systems
Authors: McKnight ME , Martin JW
Published: December 2008

A nondestructive laboratory procedure using infrared thermography for detecting air- and water-filled blisters and localized corrosion at the coating/metallic substrate interface is described. Deteriorated areas are observed in real time as varying gray levels on the cathode ray tube of an infrared thermographic camera or after digitization of the signal on a TV monitor. Digitization of the analog signal permits (1) image enhancement through signal averaging techniques, (2) association of gray levels with degraded areas, (3) quantitative analysis of the panel for amount, location, and type of degradation, (4) computerized storage of the digitized signal for dynamic analysis of the degraded coating, and (5) graphic display of thermographic images. In addition to providing a non-destructive test for assessing degradation at the coating/substrate interface, these analyses will contribute to further understanding of corrosion mechanisms and the kinetics of degradation. This knowledge will be useful in developing improved accelerated tests for predicting coating durability.
ASTM Safety Alert System
Authors: Oechsle SJ
Published: December 2008

The ASTM Safety Alert System defines a system for alerting employees on a multiemployer construction site to the degree of hazard in the area where organic or inorganic solvented and/or reactive materials are being applied. The hazards are broken down into three categories: health, flammability, and reactivity. Each hazard is quantified on a scale from zero to four or none to severe. A placard has been developed with an adhesive back that can be posted at the entry to the work area. The placard will show the rating in each category and also the personal safety equipment required to enter the work area safely.

The package that will be available from ASTM will include a quantity of placards, a quantity of posters explaining the layout and use of the system, and a series of stickers indicating the various combinations of personal safety equipment that would be required under various conditions.
Fracture Toughness and Impact Characteristics of a Hybrid System: Glass-Fiber/Sand/Polyester
Authors: Joneja SK , Newaz GM
Published: December 2008

In order to understand the damage mechanism in a glass-fiber/sand/polyester hybrid composite, it is essential to study the effects of inherent flaws or defects on the damage growth in the material. The irregular shape and presence of sharp geometric corners in the sand particles, voids, and improper interfacial bonding are factors that contribute to the weakening of the composite performance. One of the parameters influencing the defect formation is size of sand particles.

In this investigation, the thickness of glass/polyester layer is varied, while the sand/polyester layer is kept at a constant thickness. Laminates are made using different sand particle dimensions in order to investigate their influence on the performance of the hybrid composite. The combined effect of the defects is quantified by measuring the residual backing toughness provided by the glass/polyester layer after the full crack growth in the sand layer. The laminates having fine-sand particles provide better toughness properties in comparison to the coarse-sand laminates.

Impact studies are performed to evaluate the influence of defects on the hybrid composite behavior when subjected to impulsive loading. The load is applied to the glass/polyester face. The effect of thickness of the glass/polyester layer on damage initiation and propagation due to the impacting tup has been studied. It has been found that the thickness of the glass/polyester layer has a predominant influence on damage growth and mode of failure.
Characterization and Analysis of Damage Mechanisms in Tension-Tension Fatigue of Graphite/Epoxy Laminates
Authors: Jamison RD , Schulte K , Reifsnider KL , Stinchcomb WW
Published: December 2008

The mechanisms by which subcritical and critical damage develops in several lamination geometries of T300/5208 and T300/914C graphite/epoxy material during tension-tension fatigue were closely examined. A damage analogue in the form of stiffness reduction was used to provide a framework by which the sequence of damage development could be correlated with mechanical response. Stiffness reduction, measured continuously during the course of cyclic loading, was shown to provide a reproducible characteristic correlation with percent of life expended. The relationship was observed to differ markedly among lamination geometries, but for a given geometry was found to clearly indicate the partition of the mechanical response into distinct regions in these characteristic curves. These regions, moreover, were shown to be predominated by particular damage mechanisms—some already discussed in the literature, others less well-recognized.

Results of the observed damage development sequence for cross-ply and quasi-isotropic laminates are presented along with a preliminary association between this damage and the characteristic stiffness reduction curves for these geometries. The geometries used were characterized by distinct, predominant, early subcritical damage conditions. This secondary and subsequent damage development was examined in relation to known, predictable beginning state. Of particular emphasis in each case was the role of this developing damage state in the fracture of fibers in the 0-deg plies.

Damage detection and characterization was accomplished using both nondestructive and microscopic techniques. Two techniques proved to be of considerable utility: penetrant-enhanced stereo X-ray radiography and scanning electron microscopy of coupons taken from penetrant-enhanced deplied, damaged specimens.

A number of significant damage conditions, not heretofore reported, were observed: the production of interior delaminations at the 0/90-deg interfaces of [0,902]s laminates by the gradual growth of longitudinal cracks in the 0-deg plies; the existence of a dense distributed microcrack condition at all distinct interfaces of [0,90,±45]s laminates; the segregation of 0-deg fiber breaks in all laminates into zones coincidental with cracks in the adjacent plies; and, the appearance of shear fracture in 0-deg fibers associated with the passage of longitudinal splits.

Mechanisms for each of these damage conditions are proposed in terms of the micromechanics of the predominant damage condition with which they are associated and the global stress state.
Influence of Prescribed Delaminations on Stiffness-Controlled Behavior of Composite Laminates
Authors: Reddy AD , Rehfield LW , Haag RS
Published: December 2008

The effect of delaminations on the stiffness-controlled behavior of laminated composites is investigated. Four panels of [±45,0,90]2s quasi-isotropic layup are fabricated from the T300/Narmco 5208 material system, three with prescribed delaminations of different rectangular shapes and orientations. Nondestructive buckling tests and vibration experiments are conducted on these panels with clamped-free and clamped-simple support boundary conditions to assess the stiffness-controlled behavior. Free-free vibration tests are also conducted to study the influence of delamiantions on higher modes. Finite-element analyses are performed to compare with the experimental results. The findings indicate that delaminations of the size considered can be tolerated for some service conditions without dire consequences.
Materials Characterization for Matrix-Dominated Failure Modes
Authors: Whitney JM , Browning CE
Published: December 2008

Viable test methods that may be used in characterizing matrix-dominated composite properties are assessed. Special emphasis is placed on matrix cracking and delamination. Both strength characterization and fracture mechanics test methods are considered. Transverse tension, in-plane shear, interlaminar shear, and a laminate test for in situ first-ply failure are the strength tests considered. Fracture mechanics test methods discussed include the double-cantilever-beam test, a 90-deg center-notch tension test, and a free-edge-delamination tension test.
Mixed-Mode Strain-Energy-Release Rate Effects on Edge Delamination of Composites
Authors: O'Brien TK
Published: December 2008

Unnotched [±θ/0/90]s graphite/epoxy laminates, designed to delaminate at the edges under static and cyclic tensile loads, were tested and analyzed. The specimen stacking sequences were chosen so that the total strain-energy-release rate, G, for edge delamination was identical for all three layups. However, each layup had different percentages of crack-opening and shear-mode strain-energy-release rates, GI and GII, respectively. Results with composites made from T300 graphite fibers and 5208 epoxy, a brittle resin, indicated that only GI contributed to delamination onset under static loading. However, results with composites made from C6000 fibers and H205 epoxy, a tougher resin, indicated that the total G governed the onset of edge delaminations under cyclic loads. In addition, for both materials, the threshold level of G for delamination onset in fatigue was significantly less than the critical Gc measured in static tests. Furthermore, although the C6000/H205 material had a much higher static Gc than T300/5208, its fatigue resistance was only slightly better. A series of mixed-mode tests, like the ones in this study, may be needed to evaluate toughened-resin composites developed for highly strained composite structures subjected to cyclic loads.
Effect of Fatigue-Induced Defects on the Residual Response of Composite Laminates
Authors: Highsmith AL , Stinchcomb WW , Reifsnider KL
Published: December 2008

This paper is concerned with the understanding, interpretation, and engineering representation of fatigue damage development in continuous-fiber composite laminates that are fiber dominated, but have significant effects caused by damage in the off-axis plies. It is the objective of this paper to present a description of damage development under tension-tension, tension-compression, and compression-compression cyclic loading that is as complete and generic as possible in the sense that it can be used as a basis for engineering representations and interpretations of the effect of such damage on the strength, stiffness, and life of composite laminates.
A Model for Predicting Thermal and Elastic Constants of Wrinkled Regions in Composite Materials
Authors: Jortner J
Published: December 2008

Previous theoretical attempts to predict the mechanical behavior of curvedfiber composites have provided only upper or lower bound estimates of the elastic constants of orthotropic wrinkled regions. In this paper, a new model is described that extends the prior work in the following ways: (1) for a certain class of wrinkles the approach is exact in that stress equilibrium and strain compatibility are simultaneously satisfied; (2) the model can treat wrinkled regions that are non-orthotropic because of asymmetries in the wrinkle's waveform; and (3) the model explicitly provides results for all the elastic constants and the thermal expansion coefficients, of the (monoclinic) wrinkled region. For orthotropic wrinkled regions, a model also is provided for thermal conductivities. The approach is appropriate to wrinkles formed by “cooperative” distortions of reinforcement layers, in which the waveform of each layer is (more or less) in phase with the waveforms of the other layers. Implementation of the analysis is numerical, using a simple specialized finite-element formulation. Examples of the model's predictions are compared to predictions of previous analyses.
A Micromechanical Fracture Mechanics Analysis of a Fiber Composite Laminate Containing a Defect
Authors: Papaspyropoulos V , Ahmad J , Kanninen MF
Published: December 2008

The vast majority of developments in fracture mechanics have been instigated by the need to avoid fracture of metals. Consequently, these developments are based on the assumption that the material is homogeneous—an assumption that is far more palatable in the case of most metals than it is for fiber-reinforced composites. Attempts to make fracture mechanics concepts more applicable to composite materials have resulted in the emergence of anisotropic fracture mechanics approaches. But, while this simple extension of linear elastic fracture mechanics does remove the assumption of material isotropy, it still assumes the material to be homogeneous. Experimental evidence suggests that the application of anisotropic fracture mechanics to fiber-reinforced composites still leads to inconsistencies in the prediction of fracture.

This paper presents an improvement in the application of a concept that allows for direct consideration of heterogeneous material behavior in the near crack tip region. The concept is similar to the singular perturbation and matched asymptotic expansion techniques used in fluid mechanics. The problem of a fiber-reinforced composite containing a flaw is divided into a local heterogeneous region (LHR) and a global anisotropic homogeneous continuum region. In the LHR, local failure events can be individually modeled, and then related to a global fracture parameter. Specifically, a quasi-three-dimensional finite-element LHR model is used to investigate micromechanical failure events at the tip of a crack in a fiber-reinforced composite laminate. These events are then related to a global fracture event, whereupon the fracture toughness of the composite can be estimated. Computational results, although in seemingly reasonable agreement with existing experimental data, are heuristic in nature. The work represents only a preliminary effort toward possible future development of a more sophisticated predictive model.
The Toxicity of Oil Spill Dispersants to Marine Organisms: A Current Perspective
Authors: Wells PG
Published: December 2008

The toxicity of second-generation dispersants and component surfactants to a wide range of marine organisms is concisely reviewed. Recent studies are particularly emphasized. The paper offers a current perspective on oil spill dispersant toxicology, a prerequisite to understanding the toxicology of chemically dispersed hydrocarbons. Known lethal and sublethal thresholds are summarized for various dispersants (concentrated, water-immiscible, water-miscible). Existing information on the comparative toxicology of surfactants and dispersants is evaluated; the data base on a current formulation (Corexit® 9527) is thoroughly examined. Current studies in our laboratory with brine shrimp and endemic marine copepods are briefly described. Factors known to influence the toxicity of dispersants are described. The sites and physiology of toxic action of dispersants, though incompletely understood, are discussed; respiratory and nervous systems appear to be primary targets of action. Hypothesized relationships between dispersant toxicity and effectiveness, and the toxicity of chemically dispersed oil are discussed. Recommendations for future research are also given.
The Toxicity of Oil and Chemically Dispersed Oil to the Seagrass Thalassia testudinum
Authors: Baca BJ , Getter CD
Published: December 2008

Turtle grass beds, a valuable natural resource, are diminishing throughout the tropics because of damage from dredging, boats, and other factors. The toxicity of chemical dispersants and crude oil to turtle grass was determined in the laboratory to assess the potential for damage from spills occurring in the field. Studies of water-soluble fractions (WSF) of crude oil in static bioassays showed that a chemical dispersant (Corexit® 9527) increased the amount of total oil in water more than 50-fold. The toxicity of chemically dispersed oil was assessed by conventional (96-h 50% lethal concentration) methods in static systems, and the results were compared with toxicity measurements where the system was flushed after 12 h. The 12-h single-dose systems simulated certain active natural systems by the incorporation of dilution by tides and by using shorter exposure times. The rationale was verified by work with oil spills in the tropics. Using actual total hydrocarbon concentration for crude oil, dispersed oil, and dispersant alone allowed a comparison of their toxicities. Prudhoe Bay crude WSF was more toxic than dispersed oil or dispersant alone, possibly because of the large component of benzene, toluene, and C-2 benzene. The percentage of green (chlorophyllous) leaves was useful as evidence of toxicity. The importance of anatomical features such as recessed meristem and abundant leaf sheaths in protecting the growing region from waterborne pollutants was evident.
Experimental Use of Dispersants for Spill Countermeasures on Arctic Beaches
Authors: Owens EH , Foget CR , Robson W
Published: December 2008

Field experiments have been conducted on arctic beaches to assess the effectiveness of dispersants for the cleanup of stranded oil. The application of two commercially available chemical dispersants to aged and emulsified oil plots, in the intertidal zone on a semi-sheltered beach, resulted in a significant reduction of oil loadings immediately following the experiment as compared to loadings on adjacent intertidal control plots. The use of dispersants may, therefore, be of some value in mitigation of the potential adverse effects of oil immediately following stranding. In the semi-sheltered arctic environment in which the 1981 experiments were conducted (fetch up to 100 km; two-month open-water season), natural reworking of the oiled intertidal control plots over a 40-day period was effective in removing approximately 85 to 95% of the original oil loading. Further experiments in 1982 replicated the 1981 study in a more sheltered location, with a fetch area of less than 2 km, and indicate that the use of dispersants was not effective in this very low-energy environment. The conclusions drawn from this arctic experiment have a direct relevance to other coastal environments in lower latitudes.
Development and Implementation of Guidelines for Dispersant Use: Regional Response Teams
Authors: Pavia R , Smith RW
Published: December 2008

Since 1978, dispersant use guidelines have been developed and implemented for regional response teams (RRTs) in standard federal Regions IX and X, to enhance the RRTs' ability to respond rapidly to requests to use dispersants. The guidelines define the data necessary to give approval. These data include physical, chemical, and biological parameters associated with spilled oil and dispersants. A decision to use dispersants is based on balancing the economic, social, and natural resource costs associated with oil spills. Damages expected from spills not treated with dispersants are compared to damages expected if the oil is treated. The objective of the guidelines is to help minimize the damage to natural resources. Specific criteria were developed by the RRTs as minimum standards for documentation of dispersant application, including the recording of dispersant type and application rates, visual observation of dispersant effectiveness, and monitoring environmental impacts. This paper summarizes the progress of two RRTs in responding to requests for dispersant use, developing dispersant guidelines, and recommending minimum standards for documentation. Physical, chemical, and biological factors used in the decision process are also reviewed. Finally, the paper discusses the importance of resource protection and monitoring.
An Overview of Statistical Analysis of Biological Community Data
Authors: Hendrickson JA , Horwitz RJ
Published: December 2008

The types of questions usually asked of community data are categorized and used to structure the choice of analyses for any given study. Comments are offered on the relative suitability of various analyses for data acquired in well-designed studies.
Ecological Risk Assessment Based on Stochastic Age-Structured Models of Population Growth
Authors: Ginzburg LR , Johnson K , Pugliese A , Gladden J
Published: December 2008

A method is developed to evaluate the risk of a population crossing a preassigned critical level in a given period of time. The method is based on the stochastic age-structured model of population dynamics. The two-step process is suggested. The first step constructs the “effective” one-dimensional model with the autocorrelated noise term reflecting the underlying multidimensional process. The second step solves the first passage time problem in a one-dimensional context.
The Use of Risk Assessment in Developing Health-Based Regulations
Authors: Roth HD , Wyzga RE , Hammerstrom T
Published: December 2008

The six major steps in risk assessment are defined. Difficulties arising in each of the steps are discussed. The use of risk assessment by Federal regulatory agencies is briefly surveyed, and some recent legislation mandating risk assessment is listed.
Essential Features of a Laboratory Quality Assurance Program
Authors: Taylor JK
Published: December 2008

Progress in the environmental sciences is vitally dependent on reliable data resulting from complex measurement processes. Because of this complexity, the measurement process must be well designed and operate in a state of statistical control. A quality assurance program, including quality control and quality assessment procedures, denotes those features that lead to the production of data under these conditions. The rudimentary features are described together with the expected benefits. Parallelisms are drawn with a well designed manufacturing process.
An Introduction to Statistical and Ecological Software
Authors: Hensler GL
Published: December 2008

An introduction to the readily available ecological software is given along with information on obtaining documentation and programs. General statistical software useful in ecological research is also considered; some references useful in comparing large statistical packages are given.