bluuebunny/crossref_metadata_2025_split huggingface dataset:
Total Versus Dissolved Metals: Implications for Preservation and Filtration
Authors: Pennino JD 
Published: March 2009

Review of ground-water quality data obtained from wells in southwestern Ohio revealed the presence of lead, cadmium, and other heavy metals. Often, no pollution source could be discovered to account for the presence of the heavy metals. In order to establish whether sampling methods were a possible source of contamination, three possible sources of spurious heavy metal values were investigated: (1) the sample preservative, (2) the sampling equipment, and (3) suspended matter in the samples.
The results of this study indicate that painted labels on nitric acid preservative ampules, used during the period 1978 to 1980, contributed to false indications of ground-water pollution. Tests of galvanized steel and polyvinyl chloride bailers showed that this equipment was not a source of lead or cadmium. Statistical analysis of a random sample of ground-water analyses from 70 wells revealed a significant relationship between sediment and lead values. Furthermore, lead values generally increased as the amount of sediment in the sample increased. This relationship probably reflects the presence of lead in particulate matter in the water sample.
Particulate matter found in well water samples can be pieces of corroded well casing or fine sediment from the formation in which the well is screened. Since very little information is available on heavy metals in Ohio's glacial deposits, additional studies of these materials should be done to provide background data for the evaluation of heavy metals in ground water.
How Flat Is Flat?—Termination of Remedial Ground-Water Pumping
Authors: Spreizer GM , Maxim D , Valkenburg N , Hauptmann M 
Published: March 2009

Remedial actions are being initiated at many Superfund sites, and the analyses of water-quality data from these sites are being performed. The start of remediation is obvious—the system used for cleaning up is turned on; however, the determination of when this remediation is “complete” may not be clear.
With the initiation of a remedial measure, it is expected that the detected concentrations of characteristic contaminants will decrease rapidly and then level off to some asymptotic concentration. This is expected since the efficiency of remediation is generally considerably greater at higher concentrations than at lower concentrations. It is expected that some form of an exponential model, y = Cexp (-kx), will describe the system's behavior. This is especially true when ground-water pumping is the remedial measure used, as is considered in this paper.
With Superfund remediation schemes, cleanup or performance goals are set for key compounds. The cleanup is complete when these goals are attained. However, attainment of cleanup goals may be technically infeasible in certain cases and alternative criteria may be appropriate.
This paper presents a statistical methodology, based on an anticipated exponential decrease in the contaminant concentration resulting from ground-water pumping remediation. The methodology will initially predict when remedial measures can be terminated. As the remediation program continues and additional monitoring data become available, the methodology will determine whether and when preestablished concentration limits will be attained and when the equilibrium concentration can be estimated.
Evaluation of Finite-Element Models and Stress-Intensity Factors for Surface Cracks Emanating from Stress Concentrations
Authors: Tan PW , Raju IS , Shivakumar KN , Newman JC 
Published: March 2009

This paper presents an evaluation of the three-dimensional finite-element models and methods used to analyze surface cracks at stress concentrations. Previous finite-element models used by Raju and Newman for surface and corner cracks at holes were shown to have “ill-shaped” elements at the intersection of the hole and crack boundaries. These ill-shaped elements tended to make the model too stiff and, hence, gave lower stress-intensity factors near the hole-crack intersection than models without these elements. Improved models, without these ill-shaped elements, were developed for a surface crack at a circular hole and at a semicircular edge notch. Stress-intensity factors were calculated by both the nodal-force and virtual-crack-closure methods. Both methods and different models gave essentially the same results. Comparisons made between the previously developed stress-intensity factor equations and the results from the improved models agreed well except for configurations with large notch-radii-to-plate-thickness ratios.
Stress-intensity factors for a semi-elliptical surface crack located at the center of a semicircular edge notch in a plate subjected to remote tensile loadings were calculated using the improved models. A wide range in configuration parameters was considered. The ratio of crack depth to crack length ranged from 0.4 to 2; of crack depth to plate thickness from 0.2 to 0.8; and of notch radius to plate thickness from 1 to 3. The finite-element or nonsingular elements models employed in the parametric study had singularity elements all along the crack front and linear-strain (eight-noded) elements elsewhere. The models had about 15 000 degrees of freedom. Stress-intensity factors were calculated by using the nodal-force or virtual-crack-closure method.
On the Semi-Elliptical Surface Crack Problem: Detailed Numerical Solutions for Complete Elastic Stress Fields
Authors: Blom AF , Andersson B 
Published: March 2009

The p-version of the finite-element method together with carefully designed meshes is used to obtain accurate numerical solutions for complete elastic stress fields in a linearly elastic plate containing a semi-elliptical surface crack for two materials having a Poisson's ratio of 0.3 and 0.499, respectively. A priori known convergence properties are used to estimate bounds for the error in the numerical solutions. The calculated displacements are believed to be accurate at all points located not closer than 0.001a, a being the crack size, from the crack front.
It is demonstrated that pointwise values for the traditional edge stress-intensity factors KI are readily obtained with very high accuracy even when a very simple mesh and a modest computational effort are used. So-called vertex and vertex-edge intensity factors are derived which together with numerically determined eigenfunctions fully characterize the complete solution in the vicinity of the vertex where the crack front intersects with the stress-free surface.
For the nearly incompressible material, the second-order vertex intensity factor strongly influences the solution close to the vertex. In fact, the first-order vertex intensity factor, under different boundary conditions, may be of negligible importance (except for extremely small distances from the vertex). The size of the domain where the vertex singularity strongly influences the solution is of the order 0.02a.
Observations of Three-Dimensional Surface Flaw Geometries During Fatigue Crack Growth in PMMA
Authors: Troha WA , Nicholas T , Grandt AF 
Published: March 2009

A series of fatigue crack growth experiments was conducted on a transparent polymer (PMMA) using a surface flaw geometry in bending. A Newton interferometric technique was used to measure crack opening displacements and closure for four different loading histories. Results are presented for conditions of constant applied stress-intensity factor along the crack face free surface, at the crack tip in the depth direction, for constant applied load range, and for a block loading sequence.
Three distinct crack geometries are identified and are found to be a function of crack size. The crack opening displacement patterns are found to be strongly influenced by the formation of a void internal to the crack. Three distinct closure loads are identified and measured for surface flaws of various crack depths and aspect ratios. The various closure loads are used to define effective stress-intensity ranges. Life predictions, crack growth rates, and aspect ratios are used to evaluate the applicability of the various closure loads at different locations. It is found that the same closure load does not determine the best value of effective stress intensity at all points along the crack tip in the surface flaw geometry.
Some Special Computations and Experiments on Surface Crack Growth
Authors: Prodan M , Radon JC 
Published: March 2009

The new method of surface crack growth calculation under linear elastic fracture mechanics (LEFM) conditions facilitates the use of stress-intensity factor K (and in particular its ΔK range) as a tool to estimate the fatigue life of cracked plates under tensile loads. This is made possible by determining a set of parameters in order to obtain equal ΔK values and analogous crack propagation rates in two widely different specimen geometries, a plate and a standard compact type (C(T)) specimen. A comparison of fatigue lives with equivalent crack growth for both types of specimen suggests that in using the proposed procedure, the significance of ΔK values in a part-through crack is closely related to that of a through crack in a C(T) specimen.
In analyzing the surface crack growth under elastic-plastic conditions, it should be necessary to use J values in a different way than in LEFM. Appropriate references to both problems are quoted.
Growth of Surface Cracks Under Fatigue and Monotonic Increasing Load
Authors: Hodulak L 
Published: March 2009

An engineering assessment of the life time and failure conditions for components with surface cracks can be easily done using a personal computer program. The methods, assumptions and the modeling of surface crack growth used in the program are briefly described.
A more detailed comparison of calculated and observed growth of surface cracks under fatigue and monotonic increasing load shows some phenomena, which are not completely understood as yet. They are discussed in connection with the constraint variation along the crack front. Some results on constraint at the front of surface cracks and on the J-R curves for surface cracks in tension plates are given.
Alkali Silica Reaction of Concrete in Electrical Substation Piers Accelerated by Electric Current
Authors: Ozol MA 
Published: March 2009

Concrete piers supporting towers at the corners of an electrical substation are expanded and severely cracked. Eight intermediate piers show no signs of expansion, cracking, or surface deterioration. All piers were constructed (1969) of the same concrete mixture.
The corner piers are connected to both ground and the above steel structure. The intermediate piers are grounded only and not connected to the above steel structure.
The coarse aggregate (CA) is a siliceous gravel composed essentially of quartz, quartzites, and cherts. The fine aggregate (FA) is a natural sand of essentially the same composition.
Cores taken from the corner piers exhibit: a) internally cracked CA particles with cracks extending into the mortar and connecting with cracks from other particles; b) reaction rims around CA particles with adjacent pockets of dried Alkali-Silica Reaction (ASR) gel that has breached through the reaction rim; c) peripheral separations around CA particles, with peripheral cracks in the adjacent mortar, and CA particles loose in their sockets; and, d) dried ASR gel in voids, cracks, and CA sockets, commonly in association with ettringite crystals.
The determined alkali contents of the corner pier, and intermediate pier concretes were the same; .06% NA2O and .05% K2O in each, as weight percents of the concrete.
Samples from the intermediate piers show these features of ASR to a minor degree: a) rim development on some chert and quartzite CA particles; b) small gel deposits within, and near, chert and quartzite CA particles; and, c) some chert and quartzite CA particles with internal cracks that do not extend out of the particles.
Since both concretes have ASR, one to an inconsequential degree and the other to a serious degree, the difference in the condition of the two concretes is attributable to a difference in the rate at which the ASR proceeded in one versus the other.
On-site measurements of electrical potential, by Cu/CuSO4 reference cell, between the steel structure and both the pier concretes and the surrounding soil show current flow from the concrete to the soil, with strong implications that, because of the corner piers being connected to the superstructure, the potential differences and current passing through the corner concrete was larger than through the intermediate concrete.
It is proposed that the reason for the difference in the degree of the ASR in the concretes is that the ASR has been accelerated in the corner piers by greater diffusion of alkali ions under the influence of a greater electrical potential gradient than is present in the intermediate piers.
The Importance of Petrological, Petrographical and Mineralogical Characteristics of Aggregates in Very High Strength Concrete
Authors: Sarkar SL , Aïtcin P-C 
Published: March 2009

Aggregate intrinsic strength, particularly that of coarse aggregates, receives scant attention from concrete technologists and researchers as long as the w/c ratio falls within the 0.50-to-0.70 range, primarily due to the fact that the cement-aggregate bond or the hydrated cement paste fail long before aggregates do.
This, however, does not hold true for very high-strength concretes, with very low w/c ratios of 0.20 to 0.30. Compressive strength testing of very high-strength concrete has indicated that aggregates can assume the weaker role, exhibited in the form of transgranular fractures on the surface of failure, as has already been observed in some lightweight concretes.
The authors have carried out detailed petrological, petrographical and mineralogical characterization of twelve different coarse aggregates that have performed with variable success in very high-strength concrete in Canada and the United States. Suitability for such an application has been linked to a special set of lithological characteristics: the minerals must be strong, unaltered, and fine grained. Intra- and intergranular fissures, partially decomposed coarse-grained minerals, and the presence of cleavages and lamination planes tend to weaken the aggregate, and therefore the ultimate strength of the concrete.
Laser Excited Fluorescence in Criminalistics
Authors: Menzel ER 
Published: March 2009

Applications of laser-excited fluorescence can be found in numerous areas of criminalistics, including document examination, fiber analysis, serology and latent fingerprint development. This paper focuses on the latter application. The present mature procedures for laser fingerprint detection are described to set the stage for discussion of current research, which primarily deals with time-resolved imaging to take advantage of the difference between the lifetimes of substrate and fingerprint fluorescences.The principal procedure for laser detection of latent prints on smooth surfaces involves first the fuming with cyanoacrylate ester, which results in the formation of a polymer on the fingerprint residue. Thus stabilized latent prints can then be solution stained with fluorescent dyes. Porous items are treated with ninhydrin or its analogs, which react with amino acids of the fingerprint residue. Subsequent reaction with group II B metal salts yields intensely fluorescent products.Time-resolved imaging involves modulated laser excitation and gated imaging with a microchannel plate image intensifier. The critical requirement for such imaging is the identification of reagents or stains that yield lifetimes which are longer than those of the substrates (typically 1 ns or less) and also at least comparable to the laser cutoff and image intensifier turn-on time (about 5 ns). Two general approaches are presented. One involves compounds that yield long-lived d-π* intramolecular charge transfer states. The other involves chemical reactions with fingerprint residue that lead to formation of organo-rare earth complexes which display long-lived rare earth emission. The structural and photophysical features which underlie the luminescence properties of fingerprints treated with ninhydrin or its analogs and subsequently with metal salts are discussed with the aim of providing guidelines for the design of optimized fingerprint detection reagents.
Temperature and Laser Intensity Effects in Highly Resolved Fluorescence Spectra of Tetracene in Cryogenic Matrices
Authors: Velthorst NH , Gooijer C , Hofstraat JW 
Published: March 2009

Temperature and laser intensity effects on the highly resolved fluorescence spectra of the model compound tetracene in crystalline and in amorphous cryogenic solid solutions have been investigated.
In crystalline solid solutions, using lamp and selective laser excitation, the spectra show a strongly temperature dependent height, width and position of the narrow lines. Hence, accurate temperature control and stability are required for reliable identification and quantification. In amorphous solutions under laser excitation also the height and width of the narrow lines strongly depend on temperature; the line positions, however, are independent of the temperature and the choice of the matrix material.
The effect of the laser intensity on fluorescence line-narrowed spectra has been studied for tetracene in amorphous glassy and polymer matrices. It appears that already at relatively low laser powers the narrow lines show a nonlinear dependence of their fluorescence intensity, in particular when excitation is performed in regions with large absorption cross sections.
Moreover, attention will be paid to the temperature- and laser intensity dependence of hole-burning effects in laser excited spectra in amorphous matrices.
Stress Cracking Morphology of Polyethylene (PE) Geomembrane Seams
Authors: Halse YH , Koerner RM , Lord AE 
Published: March 2009

The high crystallinity of polyethylene (PE) geomembranes offers an excellent chemical resistance to harsh chemical leachates, but can be problematic with regard to stress cracking. Particularly vulnerable are field seams due to their overlapping geometry, necessity for surface grinding for removal of oxide layers, and possibility of poor quality. Using laboratory test specimens under constant load (ASTM D 2552 [modified]) it was shown that field seams can be subjected to such stress cracking.
This paper presents a fracture surface morphological study of the cracked specimens from those particular tests. Five different seam types were evaluated, compared, and contrasted under different applied stress levels. Qualitatively, the morphology patterns were grouped into five categories: long fibrous, short fibrous, flake, hackle, and lamellar. These morphologies appear to be related to the magnitude of the applied global stress. The short fibers occurred at low stress, the long fibers at moderate stress, and the flake at high stress. Hackle often appears before the plastic failure as the cross-sectional area of the specimen decreases. Lamellar, the least common structure, may be caused by a combination of a low stress cracking with local plastic failure.
What remains now is to see if this tentative classification applies to stress-cracked specimens from large laboratory tests and for field situations. If the nature of the field failure can be ascertained by comparison with the laboratory-generated categories (small and large sizes), implications to optimal seam types and/or polymer compound type may become apparent.
Influence of Geotextile Structure on Pore Size Determination
Authors: Rigo JM , Lhote F , Rollin AL , Mlynarek J , Lombard G 
Published: March 2009

Filtration performance of a geotextile is related to its capacity to retain soil particles over time without clogging. A pore size determination such as the filtration opening size (FOS) is used to assess the geotextile's filtration behavior. Standard hydrodynamic methods use a soil with a uniformity coefficient (Cu) greater than 6, with the coarser particle size value at least twice the estimated FOS value, and with a d10 four times smaller than the FOS value. The filtration opening size determination, using such a soil, is greatly influenced by the size of the coarser particles and by their fraction. Pore size has been overestimated because of these factors and because of the curve continuity. The soil nature of the gradation curve and the quantity of soil used in the test may distort pore size determination, hide some phenomena, and lead to errors in interpretation.
The geotextile structure can be characterized by the mass per unit area, thickness, density of fibers, fiber diameter, porosity, and fabrication process.
This report includes the first results of a laboratory study performed at the Polytechnical School of Montreal, the University of Liège, the University of Grenoble, CEMAGREF (Antony, France), ENEL (Milano, Italy) and the Ontario Ministry of Transports (Toronto, Canada) on the interaction between geotextile structure and filtration opening size (FOS).
Classification of Emulsified Recycling Agents
Authors: Muncy SG 
Published: March 2009

The use of pavement recycling has steadily gained momentum over the last ten years. This includes various methods of both hot and cold recycling. Recycling has proven to be a reliable alternative to conventional methods of rehabilitation. The end product is of high quality and may be compared to similar methods employing only virgin materials.
Though the use of these methods has increased, a method of selecting and specifying recycling agents has lagged behind. ASTM now has A Standard Practice for Classifying Hot Mix Recycling Agents (D 4552-87). A similar standard for emulsified products is now being investigated.
This paper presents a classification system for the selection and use of emulsified recycling agents. This classification system is derived from currently used practices and extensive field observation of the interaction between materials and methods. Terminology, methods for selection, and general use guidelines are discussed.
Recycling is an important part of any pavement management system (PMS). The Federal Highway Administration has mandated the adoption of a PMS for all states. A PMS will be used to select the appropriate rehabilitation and maintenance procedure based on accepted criteria. A standard system of classification and terminology will place recycling in its proper position within the PMS.
Several state DOTs have established specifications for emulsified recycling products. As needs vary, so have these specifications. States and regions have reduced the full spectrum of products to those serving local needs. The classification system will allow easier transfer of technology as the terminology is standardized.
The classification system defines the emulsified recycling agents by composition as well as by intended performance. With this system in place, engineers will be able to select products on the basis of equipment on hand, traffic constraints, and intended vehicle capacity. This system may be used in application from rural roads to interstate highways.