bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of EPA Animal Biology Laboratory and Company Laboratory Efficacy Data for Federally Registered Rat and Mouse Baits
Authors: Peacock DB , Palmateer SD
Published: March 2009

The authors compared the efficacy data for federally registered rat and mouse baits tested both by the U.S. Environmental Protection Agency's (EPA's) Animal Biology Laboratory and by company laboratories. We chose ready-to-use, dry bait products evaluated according to the same laboratory test protocols. The data, which included 364 tests, were analyzed in two ways. First, we made 12 comparisons based on the mean percent acceptance and the mean percent mortality. Regardless of the combination of active ingredients (diphacinone, warfarin, or prolin), the species (Norway rat or house mouse), or the efficacy criterion (acceptance or mortality), the products always did better in company tests than in EPA tests on the average. These differences were usually greater for comparisons of the mean percent acceptance than for comparisons of the mean percent mortality. Second, we determined the amount of agreement between 99 matched sets of EPA and company data. We found agreement in 65 of the comparisons. Where agreement was not found, the products failed company tests but passed EPA tests in 5 cases, and passed company tests but failed EPA tests in 29 cases. Where individual companies have performed subsequent studies, they have confirmed in their laboratories the efficacy problems discovered in the EPA laboratory. We have discussed the reasons for the differences between the EPA and company data and the steps that are being taken or should be taken to reduce these differences.
Improving Efficacy Testing of Bird-Repellent Seed Treatments
Authors: Linehan JT
Published: March 2009

To overcome certain deficiencies in field evaluation of chemical repellents used to protect corn seed from birds, a test procedure was developed in which half of each test plot was exposed to birds and half was protected by bird-tight wire mesh. This arrangement isolated the effects of bird attack from the effects of the chemical on germination and on insects and diseases of seeds and sprouts. Bird pressure was controlled by enclosing all plots with netting, and placing the birds inside. Repellency under the conditions set for a test was the “covered-minus-uncovered difference” in sprouts or sprout damage in treated plots compared with the “coveredminus-uncovered difference” in untreated plots. The results of several small-plot tests (both open and enclosed) with six candidate repellents indicated that reliable economical tests can be conducted under conditions of controlled soil and moisture and under various intensities of bird attack, to yield accurate information, heretofore unavailable, on the performance of bird repellents.
Laboratory Method for Determining the Lethal Exposure Time50 (LET50) of Contact Avicides Used in Wicked-Perches
Authors: Nichols CS , Crabb AC
Published: March 2009

A lethal exposure time50 (LET50) test was developed for laboratory use to provide a toxicological basis for the testing of acute contact avicides in wickedperches such as the Rid-A-Bird perch system. The LET50 measurement expresses the toxicity of particular concentrations of avicides that are exposed in such a manner as a function of exposure (contact) time. The correlation between field efficacy and our laboratory test should be excellent since the laboratory measurement of an avicide's dermal toxicity is carried out under conditions that simulate field exposure.
Experimental Design for Field Evaluation of Odor Attractants for Predators
Authors: Roughton RD , Bowden DC
Published: March 2009

A statistically efficient method for field evaluation of predator attractants, utilizing scent-station transects, is described. The design permits simultaneous exposure of five candidate attractants and minimizes potential bias resulting from nonuniform distribution of predators, sequential visitation by predators in space or time, residual odors, nightly variation in predator activity, and prevailing winds and other meteorological conditions as they affect vititation rates. The transect visitation data are suitable for statistical analysis.
Toward a Knowledge-Based Fire Safety System
Authors: Roux HJ , Berlin GN
Published: March 2009

Two complementary systems techniques are presented for systematically describing building fire safety. These techniques are the Decision Tree developed by the National Fire Protection Association (NFPA) Systems Concepts Committee and the Building Firesafety Model developed by the NFPA as part of a project to study residential fire safety. The Decision Tree graphically describes the alternative means for achieving fire safety, while the Building Firesafety Model is a tool for calculating the actual risks associated with fire. These tools provide an initial step toward a more rigorous approach to defining fire safety.
Design to Cope with Fully Developed Fires
Authors: Harmathy TZ
Published: March 2009

Since 80 to 90 percent of the combustible contents of building compartments are consumed during the period of fully developed fire, the conditions that are expected to prevail during this period should be given special attention in the design of buildings for fire safety. The primary purpose of such design is to lessen the danger of spread of fire and smoke beyond the confines of the fire compartment. To provide a sound basis for the design, the characteristics of compartment fires, the factors that determine them, and the mechanisms by which fire and smoke spread through the building are discussed in detail.

The most common method of protecting buildings against fire spread is compart-mentation by fire-resistant boundary elements. The shortcomings of the conventional practice of fire resistance allotment are analyzed and the principles of a recommended practice, referred to as fire tolerance design, are described.

Information on the fire resistance of building elements is usually obtained by standard tests conducted on replicas of the elements. The meaning of the test results, however, is often unclear. It is becoming more and more acceptable to procure fire resistance information either by analytical and numerical studies, or by the use of extension and prediction formulas, graphs, and tables, many of which are reproduced for the designers' convenience.

Owing to fundamental faults in the philosophy of fire resistance testing, information on fire resistance, either from tests or other means, cannot be directly utilized in the fire tolerance design. Methods of conversion between fire resistance and fire tolerance are presented, and techniques of designing for fire tolerance in stagnant and spreading fires, without resorting to fire resistance information, are outlined.

Because of the prominent role that convection plays in the spread of fire and smoke, design for fire tolerance does not provide the complete answer to fire safety. The use of self-closing doors, cavity barriers and fire stops, and flame deflectors, that cut off the paths of convective fire spread, is an essential part of the overall fire defense scheme.

An effective way of attacking the problem of spread of smoke is the pressurization of the principal shafts of the building. The danger of spread of both fire and smoke is greatly reduced by fire drainage.

The need for expert knowledge in the design for fire safety is emphasized.
Keynote Address—The Role of Research and Development in the Environmental Protection Agency's Approach to the Toxic Pollutants Problem
Authors: Gage SJ
Published: March 2009

The American Society for Testing and Materials (ASTM), through its various technical committees, performs a unique service which neither the U.S. Environmental Protection Agency (EPA) nor any other federal agencies could match through any means. ASTM provides a common and neutral meeting ground for technical experts from industry, academia, and federal agencies to freely exchange ideas without the often-present suspicion and territoriality. Through its established principle of voluntary, consensus standards development, ASTM provides a forum for all interested parties to arrive at proven and accepted methods—the importance of which cannot be stressed strongly enough. We in EPA, who are involved in the development of methodologies for monitoring environmental quality, fully appreciate the value of your efforts and pledge to continue the spirit of cooperation that has guided the work in ASTM Committee D19 on Water.
Glass Capillary Gas Chromatographic-Mass Spectrometric Analysis of Organics in Drinking Water Concentrates and Advanced Waste Treatment Water Concentrates-II
Authors: Lin DCK , Foltz RL , Lucas SV , Petersen BA , Slivon LE , Melton RG
Published: March 2009

A scheme has been established to analyze complex organic mixtures of water concentrates. It includes addition of deuterated internal standards to the concentrate, fractionation of the concentrate through a combination of extraction under both acidic and basic conditions, partitioning on a short silica gel column, and finally, analysis of the partitioned fractions as well as the unpartitioned concentrate by glass capillary gas chromatography using a flame ionization detector (GC-FID) and glass capillary gas chromatography coupled to a mass spectrometer (GC-MS). The GC-FID and GC-MS analyses are conducted on two types of wall-coated open-tubular glass capillary GC columns, one containing a nonpolar liquid phase (SP2100) and the other a polar liquid phase (SP1000).
Methods for Gas Chromatographic Monitoring of the Environmental Protection Agency's Consent Decree Priority Pollutants
Authors: Keith LH , Lee KW , Provost LP , Present DL
Published: March 2009

Descriptions of modifications to the Environmental Protection Agency's Priority Pollutants Protocol are provided that enable gas chromatographic monitoring of many of these compounds at below part per billion levels. Quality assurance studies, including analytical reproducibility, purging efficiencies, extraction efficiencies, blank interferences, and differences in internal versus external standardization were conducted.
Determination of Polynuclear Aromatic Hydrocarbons in Water and Wastewater by a Gas Chromatographic—Ultraviolet Spectrophotometric Method
Authors: Searl TD , Robbins WK , Brown RA
Published: March 2009

The U.S. Environmental Protection Agency and American industry are interested in determining the concentrations of 129 potentially hazardous compounds in water. Included on the recently issued priority pollutant list are 13 polynuclear aromatic hydrocarbons (PNAs) containing from three to six condensed rings. Exxon Research has developed a gas chromatographic, ultraviolet spectrophotometric (GC-UV) method that accurately determines 23 PNAs, including the 13, at the 0.1-ppb (microgram/litre) level and higher in industrial and municipal wastewater effluents. Alkyl-substituted PNAs can be measured and additional compounds added as desired. The method has been verified by analyzing effluents spiked with a variety of PNAs.

At the start of the analysis carbon-14-labeled benz [a] anthracene and benzo [a] pyrene internal standards are added and the sample extracted with methylene chloride. A concentrate of PNA is provided by liquid-liquid extraction with dimethyl sulfoxide; if necessary, this is followed by chromatographic separation on partially deactivated alumina. The individual PNAs are separated by gas chromatography, where eluted fractions are trapped for ultraviolet absorption measurement of the PNAs. Peaks containing the carbon-14 internal standards are assayed for radioactivity. The ratio of the final to the initial radioactivity is used to quantitate the data.

With this technique, the removal of the individual PNA by the various wastewater treatment processes has been followed.
Determination of Hexachloroacetone and Hexafluoroacetone in Industrial Wastewaters
Authors: Smith JS , Burkitt DT , Hanrahan JM
Published: March 2009

Recently, there has been a great deal of interest shown in the identification and quantitation of halogenated organic pollutants in water. Federal Water Quality Acts of 1972 and 1977 and the Environmental Protection Agency's list of priority pollutants have spurred industrial wastewater analysis. Even though hexafluoroacetone is no longer manufactured in the United States, we were interested in determining if any hexafluoroacetone or its precursors have contaminated wastewater at the low parts per billion (ppb) levels from previous manufacturing sites. Hexafluoroacetone is a toxic compound that is water soluble.

We analyzed for hexafluoroacetone by converting it to fluoroform by treatment of the aqueous sample matrix with base; a procedure derived from an infrared method described by Baker and Carlson [I]2. Headspace analysis by gas chroma tography was used to detect and quantitate the fluoroform. The method has a detection limit of 10 ppb.
Computer-Aided Fracture Mechanics Life Prediction Analysis
Authors: Peterson DE , Vroman GA
Published: March 2009

The fracture mechanics analysis and computer logic used to perform design life predictions is described. Initial part-through crack defects are analyzed under the conditions of constant-amplitude loading to predict the number of loading cycles applied before breakthrough or failure. A criterion is provided to predict the transition from part-through crack growth characteristics to through crack growth characteristics. A breakthrough criterion is also provided.
Effect of Flash Point Reduction on Jet Fuel Properties
Authors: Dukek WG , Wieland ER
Published: March 2009

Jet fuel yield and quality information were developed by a computer program from crude assay data for three different refineries on flash point and other parameters, for example, freezing point, smoke point, and aromatics content. Without regard to other product requirements, availability of Jet A (-40°C freezing point) could be increased 10 to 18 percent with a 32°C (90°F) flash point limit and 22 to 30 percent with a 27°C (80°F) flash point limit compared with the current specification flash point of 38°C (100°F). Availability gains of Jet A-1 fuel (-50°C freezing point) for similar flash point limits are larger. A combination of flash point and freezing point relaxations to 27°C (80°F) and -40°C, respectively, increases Jet A-1 volume by 80 to 90 percent.

The theoretical aspects of this study must be emphasized because the competing nonaviation demands for other distillates were ignored. Other fuel properties such as aromatics and smoke point become less critical as flash point is lowered, but the most important new U.S. crude—Alaskan North Slope—still produces jet fuel that is critical in aromatics and smoke point regardless of flash point reduction benefits.
Jet Fuel Safety and Flash Point
Authors: Carhart HW
Published: March 2009

Various nonequilibrium combustion conditions are examined and evaluated regarding their effect on safety. Tank flammability limits are indicated to depend on the ratio of empty to liquid volume when fuels of different “light ends” content are used. Altitude effects and mist ignitability are discussed as is the effect of volatility on fire spread above a fuel pool. Because information is only available for Jet A and Jet B type fuels, the author offers his estimate of the effect of kerosine flash point reduction on the various properties of importance. If the use of such fuels is to be considered, performance data should be obtained to assess the impact of flash reduction on fuel handling and performance safety.
Regulations and Industry Standards (Flammability)
Authors: Maxwell WL
Published: March 2009

A maze of rules—federal, state, county, or city statutes, plus regulations by the Department of Transportation (DOT), Occupational Safety and Health Administration (OSHA), American Petroleum Institute (API), National Fire Protection Association (NFPA), and the U.S. Coast Guard—affect Jet A fuel; any major change such as flash point reduction can have far-reaching impact. Comparing international flammability classifications, only the United States and Sweden would re-classify reduced flash point kerosine from “combustible” (flash point >38°C (100°F) to “flammable” (flash point >27°C <38°C). Among states, 36 have flash point minimums affecting kerosine and other distillates but none regulate jet fuel; if states classified Jet A/A-1 as kerosine, potential conflicts could result at lower flash points than 38°C (100°F).

Shipment regulations of the Federal Code, Civil Aeronautics Board (CAB), International Air Transport Association (IATA), and DOT provide different containers, packing, marking, etc. for Class II combustible versus Class IC flammable liquids for different modes of transport. Tank storage regulations as specified by OSHA (Standard 1910.106) and NFPA, Codes 30, 70 and 407 are similar. Conservation vents or vapor recovery systems on storage tanks might be required in certain states with reduced flash point jet fuel. The downward shift in the flammability zone with lower flash jet fuel suggests that “switch-loading” regulations should apply. NFPA Code 385 describes these procedures.

In certain parts of the world, jet fuel is also used for home heating or cooking. A reduced flash point jet fuel would probably be too hazardous as a dual-purpose kerosine, and changes in supply and distribution systems would be needed. A comprehensive investigation of each country, region, state, city, and industry is needed to assess the worldwide impact of reduced flash jet fuel.
Fuel Flash Point and Airline Maintenance Practices
Authors: Brenneman JJ
Published: March 2009

No clearly defined codes govern the safety requirements of aircraft hangar maintenance practices. The experience of United Airlines is typical of other air carriers. When piston aircraft were serviced, aviation gasoline was removed and a flash point base oil Class II liquid substituted in order to work on aircraft inside the hangar. The base oil flash point was monitored. Use of Jet A fuel made this procedure unnecessary; outside defueling is not required. If a reduced flash point jet fuel (a Class I flammable liquid) were used in aircraft, the former base oil procedure might have to be reinstituted which would increase costs. Airport fire officials and insurance underwriters would determine under what conditions a reduced flash kerosine could be handled. Probable facility changes include venting wing tanks outdoors, fitting of flame arrestors on tank and container vents, closer control of ignition sources, and general improvement in hangar ventilation.
Comparison of ASTM Specification for Kerosine (D 3699) with Jet A Fuel
Authors: Austin JD
Published: March 2009

Technical Division E on Burner, Diesel and Turbine Fuels of ASTM Committee D02 on Petroleum Products and Lubricants developed ASTM Specification for Kerosine (D 3699) for two grades of kerosine suitable for burner applications. No. 1-K is a special low sulfur grade for nonflue-connected appliances and for wick-fed illuminating lamps. No. 2-K is suitable for flue-connected appliances as well as illuminating lamps. The Tech E-I Kerosine Panel designed the No. 2-K specification to maximize conformity with Jet A [ASTM Specification for Aviation Turbine Fuels (D 1655)] and No. 1 Fuel Oil [ASTM Specification for Fuel Oils (D 396)] and to enhance bulk availability as a multipurpose product. A flash point minimum of 38°C (100°F) is specified even though several states have more restrictive legal requirements. It is estimated that almost all hydrodesulfurized Jet A production would meet the kerosine limits of color, burning quality, corrosion, and viscosity at 40°C (104°F) while some hydrodesulfurized Jet A would also meet the 0.04 weight percent sulfur limit of No. 1-K kerosine.
Acoustic Emission Measurements: HSST V-7B Intermediate Vessel Test
Authors: Hutton PH , Dawson JF , Kurtz RJ
Published: March 2009

The HSST V-7B intermediate test vessel was fabricated from 152-mm thick A533B, Class 1 steel. It was pressurized at 93°C (200°F) to 151 MPa (21 800 psig) where it failed at a flaw machined into the outer surface.

Acoustic emission (AE) generated during testing of the vessel was measured for two purposes: (1) to provide indications of distress in the vessel at locations other than the machined defect, and (2) to acquire AE data for analysis relevant to development of AE/flaw relationships for inservice reactor monitoring.

Two AE monitor systems, a Dunegan/Endevco (DE) 1032 and a Battelle Northwest (BNW) multiparameter, digital memory AE system, were used to more effectively meet the two requirements. Results and conclusions include:

∎ AE source location indications clearly followed flaw development.

∎ Growth of a flaw in 152-mm thick A533 B, Class 1 material at 93°C (200°F) produced readily detectable AE.

∎ Two separate AE monitor systems using substantially different approaches to isolating AE from the defect exhibited consistent results.

∎ AE data correlates well with stress intensity factor (K) and crack opening displacement (COD) showing a basis for relating AE to flaw severity in the pressure vessel configuration.
Discrepancies Between Film and Thermoluminescent Dosimetry (TLD) Readings at an Operating Power Reactor
Authors: Quinn DM
Published: March 2009

The results of exposure measurements using film badges and thermoluminescent dosimetry (TLD) were compared at an operating nuclear power reactor. The film badge overresponded to the high-energy Nitrogen-16 gamma rays produced under power, while the TLD did not. Discussions of charged-particle equilibrium and energy dependence are included. The cause of the overresponse was determined to be the excess pair production electrons created because of the high atomic number in the lead energy-compensating shield surrounding the film and in the film itself.
Composition and Measurement of Radionuclides in Liquid Effluent from Nuclear Power Stations
Authors: Kahn B
Published: March 2009

The radionuclide content of liquid radioactive wastes discharged from commercially operated light-water-cooled reactors in the United States is described on the basis of recent reports by reactor operators and special studies undertaken by Federal agencies. Discharges are discussed in terms of sources of radioactivity and treatment processes at thestations. Effluent values are compared with the model utilized by the U.S. Nuclear Regulatory Commission.

The radionuclide at highest concentration is consistently hydrogen-3 (H-3). Annual discharges usually range in the hundreds and thousands ofcuries at pressurized water reactors and up to 100 curies at boiling water reactors. The sum of all other fission and activation products usually totals a few curies per year; cobalt-58 (Co-58), cesium-134 (Cs-134), and cesium-137 (Cs-137) are consistently among the radionuclides at highest concentration. At least two stations have operated several years without significant radioactive liquid discharges.

Analysis of liquid radioactive waste for radionuclide content consiststypically of gamma-ray spectrometry with a germanium (lithium) detector and multichannel analyzer, liquid scintillation counting after distillation for H-3 measurements, and more elaborate radiochemical analysis for strontium-89 (Sr-89) and strontium-90 (Sr-90). Special studies at nuclear power stations have shown the presence of other radionuclides that can be analyzed only by specific radiochemical procedures. Among these are carbon-14 (C-14), phosphorus-32 (P-32), iron-55 (Fe-55), and nickel-63 (Ni-63). Approaches for including analysis of such additional radionuclides are discussed.
Acceptable Radiological Environmental Monitoring Programs: Nuclear Regulatory Commission Staff Rationale and Perspective
Authors: Conti EF
Published: March 2009

A task group of members of the U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the rationale for radiological environmental monitoring required by NRC.

The results of this group's considerations can be described as the “art” of radiological environmental monitoring, in that the group was unable to develop a tightly knit rationale for all the elements of such a program. Two major factors led to this: (1) the large number of possible nuclide pathway combinations threatened to result in specifying lower limits of detection (LLD's) much more restrictive than considered practicable, and (2) a significant number of public reassurance-type measurement requirements always remained which did not fit a dose rationale. Therefore, the topics discussed are a mixture of requirements related to dose rationale and public reassurance.

The task group concluded that radiological environmental monitoring requires a blend of two types of measurements: one type based on strict dose-related considerations and another type related to a need to make measurements which have a reassurance function.

Further, whether environmental measurement data are used to directly assess the dose, to complement radioactivity release measurements, or to confirm a negative impact on the environment, there is a need for adequate quality in the data obtained. This quality needs to be adequate to demonstrate either a correlation or lack of a correlation between facility operation and measured radioactivity levels in the environment as compared with an environmental radiation dose criterion such as 25 mrem/year.
Survey of Literature on Minority Carrier Lifetimes in Silicon and Related Topics
Authors: Ross B
Published: March 2009

Minority carrier lifetime is a property of semiconductor material, but the characteristics of this property are closely related to the device and the application for which the material is intended. While the device and application do not appear to be central to the determination of minority carrier lifetime, they can make the difference between successful and meaningless measurements. A short history of the lifetime characterization of silicon is given. Methods of measurement are briefly discussed, along with some of their advantages and pitfalls. Minority carrier lifetime data are summarized. Some of the more important sources of defects and lifetime killers are surveyed, along with speculation about phenomena that cause postfabrication degradation and potential recovery. Device processing steps that can have a catastrophic or benign effect upon the length of minority carrier lifetime are mentioned. Means of limiting lifetime reproducibly are touched upon. Based on the results of this survey, some recommendations are made.
Effects of Carrier Lifetime and End-Region Recombination on the Forward Current and Switching Behavior of Power Pin Diodes
Authors: Cooper RW , Fagg S , Paxman DH , Slatter JAG
Published: March 2009

It has been shown that the on-state current-voltage characteristic of power pin diodes can be expressed in terms of base lifetime, τB; ratio of base width, W, to diffusion length, LA; and end-region recombination effects, hp and hn. The switching characteristic can be described in terms of a normalized form of these parameters, including the current density, JT, for a range of device dimensions. Independent experimental evaluation of these parameters, together with the theories, has accurately predicted the current-voltage characteristic up to 450 A cm−2 and confirmed the general behavior of the switching characteristics of a set of pin diodes with dimensions in the range 1.5 ≤ W/LA ≤ 4.
Carrier Lifetime Measurements for Process Monitoring During Device Production
Authors: Graff K , Pieper H
Published: March 2009

Carrier lifetime measurements were performed in silicon crystals in order to characterize the quality of the material and to control the device production process. For process monitoring, floating-zone n-type silicon of high resistivity was used, since p-type silicon in general exhibits pronounced axial and radial profiles of carrier lifetime.

The influence of various atmospheres during heat treatment on the final carrier lifetime in n-type silicon was investigated. Oxygen with and without additional hydrochloric acid increased the carrier lifetime, while hydrogen, in comparison with inert gas atmospheres, decreased it. Gold, copper, and iron were found to be the main heavy metal impurities introduced into silicon specimens by heat treatment. The iron content varied considerably with the atmosphere used during annealing, showing the highest concentrations for hydrogen. Fast cooling of specimens after heat treatment produced carrier lifetimes that were unstable with the time elapsed after quenching.
Radial Lifetime Profiling on Silicon Specimens by the Photoconductivity Decay and Photocurrent Methods—A Comparison
Authors: Vieweg-Gutberlet FG , Siegesleitner PF , Stallhofer M
Published: March 2009

Radial profiles of the minority carrier lifetime of silicon specimens, obtained by the photoconductivity decay (PCD) method and the photocurrent method have been compared. The photocurrent method used on slices gives more or less the same spatial resolution as a modified PCD setup reported by Graff, used on cross-sectional bars. Some problems occur when the photocurrent method is applied to p-type silicon samples.

For each of the methods a typical application exists: the photocurrent method is an important and relatively easy-to-handle tool for the investigation of the lifetime behavior of silicon wafers during the heat treatment and oxidation process, and the PCD method enables a very fast test of the lifetime (and lifetime profiles) to be made on the starting ingot material.
Lifetime Depth Profile Measurement Method in Heavily Doped Semiconductors Using Electron Beams
Authors: Possin GE , Adler MS , Baliga BJ
Published: March 2009

A method for depth profiling the minority carrier lifetime of heavily doped semiconductors is described. The technique utilizes an electron beam to generate electron hole pairs as a function of depth. By utilizing an exact numerical model for the semiconductor current flow equations, the minority carrier lifetime as a function of depth can be determined.
Laser Scanning Technique for the Investigation of Power Devices
Authors: Engström O , Drugge B , Tove PA
Published: March 2009

A measurement technique in which inhomogeneities in lifetime or resistivity or both in large-area semiconductor p-n devices can be visualized, is described. The method utilizes a light spot that is scanned across the device area. By using a double-pass method in which the beam is scanned twice for two different bias voltages, the influence of the surface is eliminated. Absolute values of minority carrier diffusion lengths can be obtained by using a red (0.63-μm) and an infrared (1.15-μm) heliumneon laser in combination. Illuminating the specimen with light of 0.63-μm wavelength and measuring the photocurrent as a function of the space charge region width yields the diffusion length for holes in the n region. Using light of 1.15-μm wavelength in the same type of measurement yields the diffusion length of electrons in the p+ region.
Electron Microscopy Study of Erosion Damage in Copper
Authors: Ives LK , Ruff AW
Published: March 2009

Solid-particle erosion data have been reported for many materials. The mechanics of the impact process has also been examined. However, relatively little effort has been expended in studying the microstructural aspects of material response to erosion. Effects such as deformation hardening, plastic flow, and particle embedding are recognized as being important but have not been subjected to careful study. Understanding the erosion mechanism at large attack angles and accounting for differences in erosion behavior of different metals and alloys are areas where knowledge of materials response factors will be most important. In the present work surface and subsurface erosion damage in copper is investigated by transmission and scanning electron microscopy techniques.
Solid-Particle Erosion of High-Technology Ceramics (Si3N4, Glass-Bonded Al203, and MgF2)
Authors: Gulden ME
Published: March 2009

Four “engineering” ceramics were subjected to impact (single particle) and erosion (multiple impacts) under conditions which simulate a natural dust environment in the subsonic velocity regime. The target materials are hot-pressed silicon nitride (Si3N4), reaction-bonded Si3N4, a glass-bonded aluminum oxide (Al2O3), and hot-pressed magnesium fluoride (MgF2). Tests were performed with six narrow size ranges of natural quartz between 10 and 385 μm average, and five velocities for each particle size. Hot-pressed Si3N4 was also impacted with silicon carbide (SiC) under the same particle size-velocity conditions.

The results are discussed in terms of current erosion and impact models by considering particle size-velocity dependencies, appearance of the impact damage, and the basic properties and structure of the targets.

Under these erosion conditions, the four target materials exhibited widely different behavior not only in absolute amount of material removed, but also in mechanism of removal. The systems hot-pressed Si3N4-SiC particles and MgF2-quartz particles were characterized by a highly deformed, permanent surface crater with associated lateral and radial crack formation, and erosion loss was proportional to particle mass and velocity, both to the fourth power. Erosion of hot-pressed Si3N impacted with quartz particles was proportional to the third power of particle size and the first power of velocity, and loss occurred by minor chipping with no secondary crack formation. Erosion of glass-bonded A12O3 and reaction-bonded Si3N4 did not show a consistent particle size-velocity dependence. The variation is related to the two-phase structure of these materials. It was found that strength is not necessarily reduced for erosion conditions which produce appreciable material removal.
Relative Erosion Resistance of Several Materials
Authors: Hansen JS
Published: March 2009

Over 200 materials were screened by a high-velocity sandblast-type erosion test to determine their suitability for application in coal gasifier valves. Most metals had relatively similar and low erosion resistances. Ceramics and cermets such as boron carbide (B4C), tungsten carbide (WC), silicon carbide (SiC), silicon nitride (Si3N4>, and titanium diboride (TiB2), if manufactured to minimize porosity, had more than four times the erosion resistance of metals. Several coatings such as boronized molybdenum and tungsten carbide, chemical vapor-deposited titanium carbon nitride (TiCN), and electrodeposited TiB2 also proved highly erosion resistant when applied in sufficient thicknesses. Additional findings confirmed that cermet binder content and ceramic porosity are related to erosion resistance.
Erosion Damage in Carbon-Carbon Composites at Hypersonic Impact Velocities
Authors: Adler WF , Evans AG
Published: March 2009

The damage to three-dimensional orthogonal carbon-carbon composites created by particle impacts ranging from 1800 to 6000 ms-1 has been characterized for three weave constructions at both ambient and temperatures up to 3600¼C. The subsurface damage modes in the vicinity of the impact crater are described for the range of conditions investigated. Hypotheses are advanced concerning the failure modes and kinetics for the material ejected from the crater based on examination of sectioned specimens and high-speed photographic sequences.

Kinking of the longitudinal and lateral fiber bundles is found to be the primary damage mode. Kinking of the longitudinal fiber bundles under the impact site (which controls the depth of the impact crater) displays a relatively minor dependence on the bundle dimensions. The lateral extent of the impact crater is dependent on the longitudinal fiber bundle content—decreasing as the bundle dimensions increase. It is hypothesized that kinking of the longitudinal fibers leads to this removal, which is related to kinking of the adjacent lateral fiber bundles which increases with the particle impact velocity.
Mechanism of Fracture of Hard Rock Using a Drag Bit Assisted by Waterjets
Authors: Hood M
Published: March 2009

It is shown that the mechanism of rock fracture is similar both when a blunt drag bit is used to cut strong rock and when a flat-bottomed punch is pressed into the rock surface. In order to study this fracture mechanism an experimental technique was developed which involved indenting the rock specimen in a quasi-static manner, using a drag bit as the punch. The effect of directing waterjets adjacent to the bit was investigated and it was found that these jets caused a rock chip to form with lower than normal forces applied to the bit. This finding agrees with results of previous experiments where lower forces were applied to the bit during the cutting operation when waterjets were used. A hypothesis is proposed to explain the action of the waterjets on the rock to produce this reduction in the indentation force.
CAVIJET Coal-cutting parameters
Authors: Conn AF , Rudy SL
Published: March 2009

Laboratory coal-cutting experiments with CAVIJET cavitating waterjets have demonstrated the feasibility of this technology for hydraulic coal mining applications. The objective of the first phase of a developmental program, as described in this paper, was to determine the system and operating parameters required to cut coal with CAVIJETS, and to compare the results with those observed for noncavitating jets.

Comparable coal cutting was achieved with the CAVIJET, relative to high-pressure, noncavitating jets, using one-fifth the pressure and one-half the specific energy. These results suggest that CAVIJET-augmented mining devices can be developed with compact, low-pressure pumps. Thus, CAVIJET should be capable of operating with safer, lighter, more suitable support equipment, while providing all of the advantages (reduction of dust and sparks; decreased damage to cutters) of conventional hydraulic mining methods.
Characterization of Plate Steel Quality Using Various Toughness Measurement Techniques
Authors: Wilson AD
Published: March 2009

The fracture toughness properties of three steels (A516-70, A533B Class 1, and HY-130) are determined in two steel-quality levels (conventional and calcium treated). In addition, a conventional quality A543B Class 1 steel is similarly examined at two locations (quarterline and centerline). Both investigations involved comparing steels with differing inclusion structures. The primary effort was to establish the upper-shelf toughness differences found using the Charpy V-notch impact and dynamic tear tests compared with those found using J-integral determinations of JIc and KIc. The JIc determinations appeared to be more sensitive to changes in inclusion structure than either the Charpy V-notch or dynamic tear tests. This was established by comparing the toughness between quality levels and by measuring the anisotropy of toughness within a steel. Comparisons are made with the Charpy V-notch impact-KIc upper-shelf correlation values. Comments concerning the suggested graphical method for JIc determination are also given.
Tensile and Fracture Behavior of a Nitrogen-Strengthened, Chromium-Nickel-Manganese Stainless Steel at Cryogenic Temperatures
Authors: Tobler RL , Reed RP
Published: March 2009

J-integral fracture and conventional tensile properties are reported for an electroslag remelted Fe-21Cr-6Ni-9Mn austenitic stainless steel that contains 0.28 percent nitrogen as an interstitial strengthening element. Results at room (295 K), liquid-nitrogen (76 K), and liquid-helium (4 K) temperatures demonstrated that the yield strength and fracture toughness of this alloy are inversely related and strongly temperature dependent. Over the investigated temperature range, the yield strength tripled to 1.24 GPa (180 ksi) at 4 K. The fracture toughness, as measured using 3.8-cm-thick (1.5 in.) compact specimens, decreased considerably between 295 and 4 K. During plastic deformation at 295 K the alloy undergoes slight martensitic transformation, but at 76 and 4 K it transforms extensively to martensites. The amount of body-centered cubic (bcc) martensite formed during tension tests was measured as a function of elongation.
Fracture Mechanics Analysis of Pipeline Girthwelds
Authors: McHenry HI , Read DT , Begley JA
Published: March 2009

Size limits for surface flaws in pipeline girthwelds are calculated on the basis of fracture mechanics analysis. Parameters for the analysis were selected from data on a 1.22-m-diameter (48 in.), 12-mm-thick (0.46 in.) pipe welded by the shielded metal-arc process. The minimum fracture toughness of the welds as determined by the crack opening displacement (COD) method was 0.1 and 0.18 mm (0.004 and 0.007 in.), depending on the flaw location. The yield strength of the welds was 413 MPa (60 ksi). Because the toughness to yield strength ratio was high, elastic-plastic fracture mechanics analysis methods were required to determine critical flaw sizes. Four approaches were employed: (1) a critical COD method based on the ligament-closure-force model of Irwin; (2) the COD procedure of the Draft British Standard Rules for Derivation of Acceptance Levels for Defects in Fusion Welded Joints; (3) a plastic instability method based on a critical net ligament strain developed by Irwin; and (4) a semi-empirical method that uses plastic instability as the fracture criterion developed by Kiefner on the basis of full-scale pipe rupture tests. Allowable flaw sizes determined by the Draft British Standard method are compared with the critical flaw sizes calculated using critical-COD and plastic instability as the respective fracture criteria. The results for both axial- and circumferential-aligned flaws vary significantly depending on the analysis model chosen. Thus, experimental work is needed to verify which model most accurately predicts girthweld behavior.
An Elastic-Plastic R-Curve Description of Fracture in Zr-2.5Nb Pressure Tube Alloy
Authors: Simpson LA , Clarke CF
Published: March 2009

An R-curve approach was investigated with the aim of establishing a means of predicting critical crack lengths in Zr-2.5Nb pressure tubes using small fracture-mechanics specimens. Because of the elastic-plastic nature of the fracture process and limitations on the maximum specimen size, conventional R-curve methods were not applicable. The crack growth resistance was therefore expressed in terms of the crack opening displacement (COD) and R-curves were plotted for several sizes of specimens and crack lengths at 20°C and at 300°C. The effect of hydrogen on R-curve behavior at these two temperatures was investigated as well.

Conventional clip-gage methods were not suitable for this work. Crack length was determined from electrical resistance, and COD, at the actual crack front, was determined from photographs of the specimens taken during testing. Crack length and specimen size had little, if any, effect on the R-curve shape. A method for expressing crack growth resistance in terms of the J-integral was also investigated and appears to be consistent with the COD approach. The effects of hydrogen and temperature on R-curve shape are consistent with their known effects on the mechanical behavior of Zr-2.5Nb. Finally, predictions of critical crack length in pressure tubes obtained by matching R-curves to crack driving force curves are consistent with published burst-testing data.
State of the Art in Aircraft Loads Monitoring
Authors: Clay LE , Berens AP , Dominic RJ
Published: March 2009

The paper summarizes current state-of-the-art equipment and techniques for the monitoring of loads during military aircraft operation. Monitoring systems are discussed which record strain, center-of-gravity motions, and control deflections, or the occurrence of selected load conditions. The raw data are reduced to sequences of stress peaks and troughs or to tabulations of peaks and coincident values of the recorded parameters. Finally, monitoring system cost estimates are provided for typical applications to individual aircraft tracking and loads and environmental spectra survey problems.
Evaluation of a Crack-Growth Gage for Monitoring Possible Structural Fatigue-Crack Growth
Authors: Ashbaugh NE , Grandt AF
Published: March 2009

The results of an experimental and analytical investigation on the use of a precracked coupon for monitoring the effect of service loads upon fatigue crack growth in a structure are discussed. The precracked coupon or “gage” is a simple device which provides a convenient means for determining the potential damage, that is, crack growth, in a structure since crack extension in the gage is a result of loads on the structure which cause the structural damage. Experimental results are reported for gages made from two aluminum alloys and having two types of crack geometries. These gages contained either a center crack or a single crack at the edge of a hole. The effect of load amplitude upon growth of the crack in the gage as a function of the crack growth in the structure was investigated. All tests were conducted under constant-amplitude cyclic load. The theoretical model is developed to predict the correlation between the growth of the cracks in the gage and in the structure. Two areas of major importance in the analysis are the load transfer from the structure through the ends of the crack gage and the crack-propagation law for the crack growth in the gage and in the structure. Comparison of the analyses and the experimental results is made.
Development of a Fatigue Lifetime-Load Spectrum for a Large-Scale Aluminum Ship Model
Authors: Birmingham JT , Marchica NV , Borriello FF , Beach JE
Published: March 2009

The fatigue load spectrum to be applied to the 30-m aluminum ship-evaluation model (ASEM) is presented. The ASEM will be tested in the David W. Taylor Naval Ship Research and Development Center, Carderock, Maryland. Spectra developed for design, analysis, and test purposes are given, based on a reference lifetime-load spectrum developed for a 90-m aluminum ship. Selected ship trial results that provide the basis for developing the lifetime-load spectrum for the 90-m ship are also presented. Results of sensitivity studies of fatigue crack growth indicate that a repeatable 1/100-year block spectrum, sequenced in a low-to-high-to-low order is a practicable compromise for fatigue testing ASEM.
Flight-by-Flight Spectrum Development
Authors: Denyer AG
Published: March 2009

A method of developing the design flight-by-flight sequenced stress spectrum at any location within the primary airframe structure is presented.

The procedure commences with the applicable procurement specifications for the aircraft and concludes with the detail's local stress spectrum suitable for fatigue and fracture mechanics analyses or testing. The stress spectrum is created within a computer program that utilizes input data comprising mission profiles, structural location data, libraries of load factor exceedance data, balanced external load conditions, and corresponding internal loads solutions. The output consists of the spectrum in tabular form and the time trace graphs of the stress amplitude.

Included is a typical spectrum developed for a variable geometry bomber with terrain-following capability, and discussion as to load sequence effects and the structural internal loads solutions necessary to describe the stress trace on a mission-by-mission basis.

Finally, the system-generated spectrum is discussed in terms of its effect on fatigue and fracture mechanics analysis.