bluuebunny/crossref_metadata_2025_split huggingface dataset:
Closure Measurements via a Generalized Threshold Concept
Authors: Marci G , Castro DE , Bachmann V 
Published: March 2009

Fatigue thresholds have been determined for Inconel 617 and Ti-6Al-4V that are unaffected by any closure phenomenon. These results show that a nonpropagation condition exists between Kop and Kmax of unique amplitude ΔKT which is unaffected by the position between Kop and Kmax. This experimental fact opens up the possibility of measuring the dividing point Kop (fixing the ΔKeff) based on a propagation/nonpropagation criterion. Three such test methods are proposed. Results of these measurements are compared with Kop determinations via load-displacement curves made in parallel on Inconel 617. Comparison of both results show that they contradict each other.
It is concluded that the two different experimental procedures determine and characterize two independent phenomena affecting the fatigue crack growth process differently. Characterizing the two different phenomena by Kop is incorrect.
Load-Point Compliance for the Arc-Bend/Arc-Support Fracture Toughness Specimen
Authors: Baratta FI , Kapp JA , Saunders DS 
Published: March 2009

The primary objective of this work is to provide the theoretical computation of load-point compliance for the arc-bend/arc-support specimen and some experimental verification of these predictions. This specimen is a segment of an annular disk loaded in three-point bending with the roller supports positioned at the inside surface.
Load-line compliance was determined principally by utilizing Irwin's equation that relates the compliance rate of change with crack length to the strain energy release rate. The strain energy release rate was determined from the stress intensity solution available in the literature for this sample. Corroboration was also provided by utilizing boundary collocation, boundary integral element (BIE), and finite element (FEM) methods. Representative cases were experimentally tested to confirm theoretical and numerical results. During the tests, it was also found that duplication of idealized support and fixture conditions was extremely important with regard to accurate measurement of load-point compliance.
Two statically equivalent models were used to calculate the load-line compliance using the numerical methods. The first we call Model 1, where the load point is fixed and the roller reactions are applied at the appropriate location. The second we call Model 2, where the load is applied at the load point and the roller reaction points are fixed in the appropriate manner. Although both models are statically equivalent, significantly different load-line compliances are obtained depending upon the model chosen.
Experimental results were also obtained. Specimens were tested with machined slots to simulate a crack and other specimens tested had fatigue cracks. The measured compliances were found to agree with Model 2 results in some cases, with Model 1 in others, and with neither in still others.
Accelerated Testing Methods for Evaluating Polyolefin Stability
Authors: Gray RL 
Published: March 2009

Most polymeric materials are subject to oxidation; the rate of oxidation depends on the polymer, fabrication methods, and end use conditions. Oxidation of polyolefins can result in discoloration and loss of physical properties such as elongation, impact strength, tensile strength and flexibility. Antioxidants and light stabilizers protect polyolefins against oxidation by controlling molecular weight change and the ensuing loss of physical and mechanical properties.
Careful evaluation of the long-term performance of polyolefins is critical to the successful development of new stabilization systems. While real-time outdoor exposure of materials is desirable, it is usually not practical due to the exposure times required. Consequently, several accelerated aging methods have been developed. This paper will discuss and compare commonly used accelerated test methods.
The High pH Chemical and Radiation Compatibility of Various Liner Materials
Authors: Whyatt GA , Farnsworth RK 
Published: March 2009

A flexible membrane liner has been proposed to line a concrete vault in which liquid low-level radioactive waste will be solidified. High-density polyethylene (HDPE) and polypropylene liners were tested at the Pacific Northwest Laboratory in an EPA method 9090 format to determine their chemical compatibility with the waste. Radiation effects were also investigated. The liners were immersed in a highly caustic (pH&gt;14), primarily inorganic solution at 90°C. The liners were subjected to radiation doses up to 38.9 Mrad, which was the expected dose the liner would receive over a 30-year life inside the vault. Recent changes have placed the liner outside the vault.
The acceptance criteria for judging the compatibility of the liner with radiation should be different than those used for judging chemical compatibility. The radiation damage over the life of the liner can be simulated in a short-term test. Both HDPE and polypropylene liners were judged to be acceptable from a chemical and radiation standpoint when placed outside of the vault, while several other liners were not compatible. Radiation did not have a significant effect on chemical degradation rates.
Development of a Short Term Testing Method for Welded Liners
Authors: Schmachtenberg E , Bielefeldt KF 
Published: March 2009

One of the critical areas of a sealing made of polymer liners is the seam. The difficult and often changing conditions during welding on the site are the reason for this. Since nondestructive testing methods do not control the adhesion of the junction, destructive testing of welded samples is necessary.With the control of the welding parameters during the welding process, constant quality can be guaranteed. Therefore it is of great interest, to find testing methods which allow to improve the quality of the seam in a short term testing procedure. This way, the parameters for the welding process and seam quality can be optimized on the site.
In a reseach project, sponsored by the German Department of the Environment and performed by the Süddeutsche Kunststoff Zentrum, several tests on welded samples were carried out, related to the different properties. To test the adhesive forces in the seam, peeling tensile tests at elevated temperatures and constant loads allow best distinction. Correlations between time to failure in the long-term peel test and geometry of the seam could be found. For correlations between ageing of the polymer material caused by the welding and internal stress in the seam, no simple test procedure could be found up to this day. The project will be continued.
Use of Thalassia and Its Epiphytes for Toxicity Assessment: Effects of a Drilling Fluid and Tributyltin
Authors: Macauley JM , Clark JR , Pitts AR 
Published: March 2009

Concurrent 12-week laboratory and field studies were conducted to determine toxicity of the suspended particulate phase (SPP) of drilling fluid to Thalassia testudinum and its epiphytes. Test systems were treated once per week to achieve nominal concentrations of 100 mg/L SPP. Chlorophyll content of Thalassia leaves and epiphyte biomass and chlorophyll content were monitored during each test. Laboratory exposures were conducted in 7-L, flow-through (7 L/h) microcosms consisting of Plexiglas cylinders containing intact cores of Thalassia from a local seagrass bed. Field exposures were conducted in water-tight Plexiglas chambers (2 by 2 by 1.5 m) placed over test plots in a seagrass bed for 24 h during SPP additions. The chamber base was buried several centimetres into the sediment to minimize water exchange. Drilling fluid exposure had no significant effect on chlorophyll a or b content of Thalassia leaves in laboratory or field tests. Epiphyte biomass was reduced after 6 weeks of intermittent exposure to SPP in laboratory and field tests. After 12 weeks, epiphyte biomass had increased to densities similar to control values.
Tributyltin chloride (TBT-Cl) was tested only in laboratory systems, using weekly treatments for 6 weeks. Nominal test concentrations ranged from 0.2 to 50 μg/L. Leaf protein and rhizome carbohydrate content of Thalassia were employed as effect measures in the TBT-Cl test. Leaf concentrations of chlorophyll a and b were not affected by exposure to TBT-Cl at nominal concentrations ⩽ 50 μg/L. Leaf protein and rhizome carbohydrate concentrations were reduced by exposure to 50 μg/L TBT-Cl. Epiphyte biomass was reduced after exposure to 50 μg/L TBT-Cl for 6 weeks; concentrations ⩽ 20 μg/L had no effect on epiphyte biomass.
A Plant Toxicity Test with the Moss Physcomitrella patens (Hedw.) B.S.G.
Authors: Morgan EL , Wu Y-CA , Young RC 
Published: March 2009

A method for detecting toxicity to a representative primary producer was developed and tested using the moss Physcomitrella patens (Hedw.) B.S.G. Cultures of the moss were maintained on solid minimal medium in a growth chamber with a day length of 17 h and a temperature of 23 ± 1°C. Two stages of the moss life cycle (spore and gametophore) were cultured for five weeks in the laboratory while being exposed to various toxic treatments.
Cultures were exposed separately to six different salt solutions (aluminum sulfate, barium chloride, boric acid, cadmium chloride, cobalt chloride, and lead nitrate), a mineralized-acidic leachate, and a coal combustion fly ash leachate. After five weeks' exposure, morphological changes, dry weight, chlorophylls a and b, and total chlorophyll measurements were used as criteria to reflect dose-effect relationships.
Regenerating clones were frequently morphologically aberrant, and no regenerants were observed at higher concentrations of most treatments. Increasing toxicant concentrations generally reduced the dry weight and chlorophyll contents of moss cultures (P ⩽ 0.05). No significant differences in response variables between spore and gametophore cultures were found, and dose-linked changes in fresh weight were similar to those for dry weight.
Cadium chloride and aluminum sulfate treatments had the most negative influence on moss dry weight and chlorophyll content; boric acid and barium chloride concentrations were the least toxic. The fly ash leachate did not appear to be toxic, possibly due to antagonistic chemical interactions in the fly ash/limestone scrubber leachate treatments.
Millet Root Elongation in Toxicological Studies of Heavy Metals: A Mathematical Model
Authors: Wang W , Elseth G 
Published: March 2009

Plant seed germination and root elongation, the first phase of plant development, are sensitive to adverse environmental stress. The objectives of this study were (1) to use a millet root elongation method for measuring phytotoxicity of heavy metals and (2) to develop a mathematical model to relate the phytotoxicity of the metals to the root elongation effect and also to provide a basis for linear transformation of the data. The results show that the order of decreasing phytotoxicity of the metals is Cu, Ni, Cd, Cr(VI), Zn, Mn, and Ba. The metal toxicity is on the same order of magnitude in the millet, fish, and duckweed tests.
A mathematical model was developed: P−PMPM =A[M] BK⁢+ [M]K⁢+ [M] where A, B, and K are constants under conditions where metal concentration M is the only experimental variable. PM is the root elongation in the presence of added metal ions and P is that in the control group.
A computer program has been developed to calculate the theoretical values of these metals. These values are in good agreement with experimental values. This model is likely to be applicable to other toxicity tests as well.
The Role of Chlorophyll Fluorescence as a Bioassay for Assessment of Toxicity in Plants
Authors: Miles D 
Published: March 2009

The typical green terrestrial plant is well adapted to sensing and reporting significant changes in its environment. This allows native plants growing in natural settings to be used to assess changes that might be toxic to plant or animal tissue. The basis of this bioassay is the chlorophyll molecule, which serves as an intrinsic fluorescent probe of the performance and capacity of photosynthesis. Under normal conditions, 97% of the light energy absorbed by chlorophyll is converted to biochemical forms of energy in photosynthesis. Stress conditions can reduce the rate of photosynthesis, disturb the pigment-protein apparatus, or block the light-driven photosynthetic electron transport in the chloroplast. This results in an increased loss of absorbed light energy of 6 to 10% via chlorophyll fluorescence with a peak in emission at 683 nm at physiological temperatures. The inverse relationship between in vivo chlorophyll fluorescence and photosynthesis has long been known as the Kautsky Effect.
Light-induced chlorophyll fluorescence from dark-adapted leaves can be recorded with portable, sensitive instruments using intact leaves. This nondestructive method essentially monitors the physiological well-being of the plant. Any stress including disease, nutritional stress, water, temperature, radiation, and chemical stress can be quickly and accurately recorded. The overall photosynthetic process can be thought of as a series of sensitive sites connected to the fluorescent photosynthetic reaction center, which respond to a large number of different insults and report these effects as a change in fluorescence. Chlorophyll fluorescence in intact native plants can be used to assess toxicity in the environment or in a laboratory bioassay.
The General Problems of AE Sensors
Authors: Higo Y , Inaba H 
Published: March 2009

The general problems of AE sensors are overviewed. The effects of mounting conditions of sensors on the sensitivity are discussed. then the sensitivity measurement methods are compared. The results of a sensor's sensitivity, obtained by NBS and by the Hatano method show that there is very little difference between them.
The convenient calibration method for sensor sensitivities, especially the “acoustic pressure method” and the “pencil lead fracture method” are discuss ed. The characteristics of lead, specially standard pencil lead from JAEWG which produce very stable reproducible AE signals, was demonstrated. The characteristics of the lead is quite similar to the lead produced in 1975. Then sensor sensitivities were obtained by the standard lead and are compared with the results of the reciprocal method.
Detection of Impact Damage in Composite Bi-Axial Test Specimens by Use of Thermally-Activated Acoustic Emission
Authors: Whittaker JW , Brosey WD 
Published: March 2009

Acoustic emission (AE) produced during thermo-mechanical loading of composite materials is known as thermo-acoustic emission (thermo-AE). When thermally cycled, coupons of various composite materials have been shown to produce quantities of AE which are directly proportional to the damage level. This work demonstrates the applicability of thermo-AE monitoring to an engineering structure.
Impact-damaged bi-axial composite test specimens were thermally cycled and their AE response recorded. An undamaged specimen produced little AE while damaged ones generated widely varying amounts. For damaged specimens, the thermo-AE was found to originate primarily in the damaged regions. Damaged specimens produced AE as a function of increasing and decreasing temperature but the effect was not repeatable. More severely damaged specimens produced copious amounts of AE. It was not possible to determine the source(s) of the emission.
The Need for Improved Use of Geologic Data in Ground Water Investigations
Authors: Regan PT , Conte JA , Mitchell MM 
Published: March 2009

In our view, the predominant cause of many poor feasibility studies, irrational risk assessments, and failed remediations has been the lack of a sound understanding of the physical characteristics of the aquifer system. Specifically, we refer to the lack of attention to detailed, geologic descriptions of aquifer materials during drilling and the subsequent interpretation of the geologic factors that control the three-dimensional shapes of permeability fields. The environmental industry has generally underutilized the potential benefits of better prediction of aquifer geometries and, therefore, more cost-effective exploitation of geologic conditions. We urge a return to the roots of geologic practice that historically formed the basis for ground water investigations.
In this paper, we propose a retrograde and not entirely innovative method that is based on classical geologic principles. This method depends on the process of developing a detailed evaluation of the physical features of the aquifer skeleton. Hydrogeologic investigations must be based on detailed geologic descriptions and interpretations of complete sections of all boreholes to define stratigraphy and interpret depositional environments. In cases where structural features control ground water flow, detailed measurements of orientations and densities of fabric elements are essential. These interpretive tools provide the physical foundation that will support the remarkable equation-solvers (computer models) which have become so popular. We suggest that cost-effective solutions to problems of contaminant migration in flow systems that may be dominated by advective transport require better prediction of the spatial distribution of permeability fields between widely spaced data points. Better prediction can only be accomplished through refined geologic interpretations based on detailed and reliable field data.
A Proposed Strategy for Assessing Compliance with the RCRA Ground-Water Monitoring Regulations
Authors: Parsons AM , Davis PA 
Published: March 2009

To satisfy the Resource Conservation and Recovery Act (RCRA) ground-water monitoring regulations, a hazardous waste management facility must have a ground-water monitoring system consisting of at least one upgradient and three downgradient wells and show that the downgradient wells are capable of immediately detecting a statistically significant amount of contamination at the water table. Because the regulations are subjective, it is often difficult for the owner/operator and the regulator to assess whether a monitor-well network satisfies the regulations. A probabilistic strategy is presented which satisfies the regulations and attempts to minimize subjectivity in evaluating the performance of a monitor-well network.
The proposed strategy is based on a determination of the likely ground-water flow paths through both the unsaturated and saturated zones and ground-water travel times. The approach involves three stages of analysis: 1) optimization of monitor well location, 2) evaluation of the sampling interval, and 3) assessing the monitor-well network performance through time.
Techniques for Quantifying the Recharge Rate Through Unsaturated Soils
Authors: Knowlton RG , Parsons AM , Gaither KN 
Published: March 2009

Sandia National Laboratories recently designed a sampling and analysis strategy to implement several techniques for quantifying the recharge rate through thick unsaturated, unconsolidated alluvium. Several methods are employed to estimate the recharge rate, including a soil-physics based (i.e., Darcy's law) method, a chloride mass balance technique, a stable-isotope method, bomb-pulse tritium method, and 36Cl techniques. Each of these techniques yields an independent estimate of the recharge rate which may be used to define background percolation rates of conservative solutes, to approximate the upper boundary flux condition for numerical flow and transport modeling of the site, or as calibration criteria in flow and transport modeling.
The soil-physics based approach is an indirect means of estimating the recharge rate through the application of Darcy's law with measured hydraulic characteristic data. The chloride mass balance method assumes piston displacement to estimate the recharge rate utilizing cumulative chloride versus water content data. The stable-isotope method is a tracer technique used to estimate the transport of the isotopic species deuterium (D or 2H) and 18O in the water molecule (H218O and HD16O), which in turn allows for the determination of the recharge rate. The tritium and 36Cl versus depth profiles can be used to estimate soil-water movement rates and soil-water age.
An Effective Monitoring Screen for Fine Sand Aquifers
Authors: Gillespie GA 
Published: March 2009

Collecting sediment free samples of low turbidity from monitoring wells installed in fine sand aquifers has been a difficult problem. Wells are often screened in aquifers containing thin lenses of silts and clays having a formation effective size of 0.1 mm (0.004“) or less. Fine sand silty formations are common to the California Bay area where wells, at depths of 6 to 15 meters (20 to 50 feet), are used to monitor landfills. Most of these wells use a conventional design consisting of a 5 cm (2 in.) or 10 cm (4 in.) diameter slotted or wire wrap screen with a filter pack externally placed around the screen to retain the fine sediment. Many of the wells are not useful because they do not provide clear, sediment free samples at reasonable sampling rates. Often, the wells are purged dry before the required purge volumes are removed.
In July, 1988, EMCON Associates installed a series of preassembled, dual walled screens filled with a fine filter pack around the Palo Alto, California landfill to monitor these fine sand aquifers at two different depths. Numerous tests were conducted to determine turbidity, pumping, and recovery rates for three wells that used 0.43 × 0.28 mm (40 × 60 # US Sieve) filter packs. The filter pack passed a #40 Sieve and was retained on a #60 Sieve.
This paper describes well development procedures, methods and measurements, and test results. Based on test results over a simulated four year sampling period, the following results have been achieved. 1. After the wells were stabilized, turbidity readings were consistently less than 20 Nephelometric Turbidity Units (NTU). Sediment was almost nil. 2. Using effective well development techniques, sampling and well recovery rates in fine sand formations can be improved so wells can be sampled in less than one hour. 3. There is no evidence of plugging of the dual walled screens during a simulated four year sampling program.
A Field Investigation of Ground-Water Monitoring Well Purging Techniques
Authors: Maltby V , Unwin JP 
Published: March 2009

A field investigation of commonly-used monitoring well purging techniques was conducted under different conditions including type of pump, pump inlet location, and the use of packers. Tracers including deionized water, fluorescent dye, and lithium chloride, were used to define the amount of stagnant water at any given time in the pump discharge. Tests were conducted in shallow 5 cm (2 in) diameter wells. The effects of drawdown were examined.
Tests conducted in the absence of drawdown with the pump inlet in a fixed position at or above the screen showed a highly variable and unpredictable inclusion of stagnant water. The use of packers did not completely prevent the inclusion of stagnant water into the pump inlet. The inclusion of stagnant water into a sample was minimized by purging from some distance above the screen followed by relocation of the pump inlet into the screen for sample collection. In wells where drawdown occurred during purging, stagnant water inclusion was minimized by reduced pumping rates to allow for sample collection during periods of well recharge. Real time monitoring of indicator parameters such as pH, temperature and specific conductance was not generally successful in indicating when purging was complete.