bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brood Size and Neonate Weight of Daphnia magna Produced by Nine Diets
Authors: Cowgill UM , Hopkins DL , Applegath SL , Takahashi IT , Brooks SD , Milazzo DP 
Published: December 2008

The purpose of this study was to discover which of nine diets would produce the largest mean brood size in Daphnia magna. Two media, one inorganic and one organic, were employed to culture three green algae: Selenastrum capricornutum, Ankistrodesmus convolutus, and Chlamydomonas reinhardtii. In addition to single algal foods, mixtures of algae were also employed. These consisted of S. capricornutum and C. reinhardtii, which were fed in varying quantities. A synthetic diet of fish chow and alfalfa served as a control. All algal diets were bacteria-free.
Neonates were acclimatized in autoclaved Lake Huron water and reared on one of the nine diets for five weeks. Demographic studies were carried out on the progeny of these acclimatized adults. First broods began to arrive after seven days. Thereafter, every other day, neonates were collected, counted, and weighed. These data presented in this study are based on 49 982 neonates.
Daphnia magna consuming algae reared on inorganic medium were less productive than those consuming algae reared on organic medium. The largest mean brood size was obtained from the mixed algal diet reared on the organic medium while the smallest mean brood size was produced by the synthetic diet. Large broods generally consisted of lighter individuals (10.8 μg per neonate) than those produced in smaller broods (20 μg per neonate). The evolutionary significance of this observation, as well as its effect on chronic life cycle studies, is discussed.
Corrosion Test Loop
Authors: Yau T-L , Webster RT 
Published: December 2008

In order to study the corrosion of zirconium under heat-transfer conditions, a corrosion test loop has been set up at Teledyne Wah Chang Albany. The major components of this test loop are a 37.85-L (10-gal) tank, a zirconium centrifugal pump, a heat-transfer heater, a vertical single-tube heat exchanger, and monitors for temperature, pressure, and flow speed at critical areas. Specimens were 0.9-m (3-ft) long tubes and wires, which were and were not subjected to a heat flux, respectively.
Tests of zirconium versus 50% sulfuric acid were conducted. Test results indicate that the effect of heat flux on zirconium in 50% sulfuric acid at about 160°C (330°F) is negligible. However, acid concentration may change in the process because of vaporization, imperfect sealing, condensation, and so forth. When the acid becomes too strong, zirconium will be susceptible to localized corrosion.
Corrosion of a Mild Steel in Distilled Water and Chloride Solutions: Development of a Test Method
Authors: Francis PE , Mercer AD 
Published: December 2008

Mild steel is the most common structural material and is used in a wide range of environments. However, there are few systematic data on the effects of operating parameters on corrosion behavior in immersed conditions. To obtain such data, a suitable test method is required in which parameters affecting the corrosion process are carefully controlled.
Dissolution of borosilicate glass vessels in water at temperatures above 60°C was shown to lower significantly the corrosion rate of steel in distilled water. The method of aerating the solution was also important. A new test apparatus is described in which the above problems have been overcome and other parameters are capable of more precise control.
Some data obtained with the new test cell are given to validate the design. The data demonstrate the effect of dissolved oxygen on the corrosion of steel in distilled and chloride-containing water at temperatures up to 90°C.
Electrochemical Methods for Evaluating Corrosion Inhibitors in Strong Acid Systems
Authors: Dean SW , Woodroof RA , Nichols J 
Published: December 2008

Electrochemical techniques have been evaluated for determining the performance of corrosion inhibitors in oil well acidizing solutions. Tests have been made with a variety of corrosion inhibitor blends in hydrochloric acid over a range of concentrations using carbon steel electrodes. Two different scan rates were evaluated. Longer term immersion tests were made with the same inhibitors to evaluate the degree of inhibition and development of pitting.
Reverse scan polarization was found to produce anodic hysteresis loops similar to what is observed with passive alloys in chloride containing environments. A number of parameters from the reverse scan polarization hysteresis loop have been examined for correlation with pitting tendency. The return potential anodic corrosion rate appears to have merit for showing pitting tendency. The pitting tendency seems to be most severe when the inhibitor is at a relatively low concentration. The poor correlation seen between the 16-h mass loss corrosion rates and the electrochemical corrosion rate estimates is probably caused by inhibitor exhaustion in the mass loss results. Polarization scan rate effects also showed that inhibitor adsorption kinetics affected the anodic polarization parameters.
A Technique for Characterizing Crevice Corrosion Under Hydrothermal Conditions
Authors: Jain H , Ahn T-M , Soo P 
Published: December 2008

A technique was developed to monitor crevice corrosion of Grade-12 titanium in a high magnesium synthetic brine under hydrothermal conditions. The current between the cathode and anode and the potential of the whole crevice assembly provide information on the various stages of corrosion. Occasionally, the decoupled potential of the cathode and anode are measured to give supporting information about the crevice conditions. A parallel test is run on a specimen that has small wells to collect crevice solution whose pH is determined at room temperature.
The current/potential results show that the crevice corrosion incubation period for a Grade-12 titanium crevice formed between two Teflon® plates is approximately two days at 150°C. Optical and scanning electron microscopy (SEM) observations show that the corrosion starts as isolated pitting that spreads along the surface as shallow pits. The corrosion conditions change significantly as the titanium oxide corrosion product fills the crevice, and the rate of corrosion may be greatly reduced after several days. The rate of crevice corrosion of commercial purity (Grade-2) titanium under similar conditions is approximately three orders of magnitude higher. In this case, active dissolution of metal starts during the initial heating of the autoclave, and the incubation period is negligible.
Interstitial Dislocation Loop Nucleation and Growth and Swelling Produced By High-Energy Cascades
Authors: Yu J 
Published: December 2008

Structural materials for advanced energy sources, such as magnetically and inertially confined thermonuclear reactors, are subjected to a radiation environment that produces high-energy displacement cascades and transmutation products, which includes helium. We address these characteristics and formulate their effect on the microstructural evolution of a material.
We consider that, immediately after a high energy cascade event, a vacancy-rich region exists near the primary event site and that an interstitial-rich zone, formed by collision chains, exists some distance from the primary event site. Transmutation-product helium can diffuse into the vacancy-rich zone and stabilize bubble nuclei that will later grow if sufficient vacancies and helium atoms diffuse to the nucleus. These bubbles are the sinks for excess radiation-produced vacancies. The excess radiation-produced interstitials migrate and bond; if the binding energy is high enough, a di-interstitial is considered to be a stable dislocation-loop nucleus. The loop nuclei grow if they receive more interstitials than vacancies; this represents material swelling since the bubbles do not cause a lattice contraction to offset the dilation caused by the growing dislocation loops.
Consider that the interstitial-loop growth process can be represented by a Langevin equation. If the growth process at time t is assumed to be dependent only on the instantaneous interstitial concentration and instantaneous microstructural state (dislocation, cavities, and grain boundaries) and independent of previous history, the growth process can be considered to be a Markov process. Application of an equivalent Fokker-Planck equation allows deduction of an interstitial-loop nucleation and growth equation, the solution of which yields an interstitial-loop distribution function.
Use of appropriate material parameters gives the incubation and growth regimes of swelling and also allows a determination of the maximum swelling temperature. At a vacancy and interstitial production rate of 1021 m−3 s−1, these results predict a maximum swelling temperature of 117°C for aluminum, 550°C for stainless steel, and 1100°C for molybdenum. These values are in good agreement with experimental results.
Basically, the maximum swelling temperature is found to be a function of only sυ, ευf/ευm, (ρN + ρl), and ˙Np. The maximum swelling temperature increases as (ρN + ρl), ˙Np, and ευf/ευm increase and decreases as increase and decreases as sυ increases. Here, sυ is the vacancy formation entropy, ευf is the vacancy formation energy, ευm is the vacancy mobility energy, ρN is the network dislocation density, ρl is the dislocation loop density, and ˙Np is the production rate of vacancies and interstitials per unit volume under irradiation.
Phase Stability in Fe-15 Ni-x Cr Alloys Under Ion or Electron Irradiation
Authors: Stubbins JF 
Published: December 2008

Three high-purity Fe-Ni-Cr alloys have been irradiated with heavy ions and with electrons at 450, 550, and 650°C to doses up to 60 dpa. The heavy ion irradiations were carried out with Ni6+ ions, and specimens were irradiated both with and without helium preinjection. The electron irradiations were carried out in a high-voltage electron microscope (HVEM) on specimens without helium preinjection. The alloy compositions were Fe-15 Ni-10 Cr, Fe-15 Ni-16 Cr, and Fe-15 Ni-20 Cr, all with low carbon levels. The latter two of these compositions are austenitic at room temperature, whereas the first can include martensite on rapid cooling. According to the computer calculated phase diagrams of Watkins et al, all of these alloy compositions would be metastable at the lowest irradiation temperature in the present study, but the austenitic phase structure should be stable in all of the alloys at the highest irradiation temperature.
Voids were formed in all of these alloys during irradiation at 650°C to 30 dpa, and swelling levels at that dose were independent of the presence or absence of preinjected helium. The more interesting irradiation behavior consisted of irradiation induced phase transformations, predominantly during irradiation at 450°C. The Fe-15 Ni-16 Cr alloy precipitated a fine distribution of M23C6 after 30 dpa at 450°C under heavy ion irradiation. Similar precipitates were not found in either of the two other alloys under similar irradiation conditions. The formation of these precipitates in a low carbon alloy was surprising. The precipitates were nucleated uniformly and were not associated with dislocation loops or other microstructural features.
The more striking irradiation induced phase transformation was the evolution of austenitic regions in the martensitic laths in the Fe-15 Ni-10 Cr alloy during irradiation at 450°C. This martensitic reversion reaction seems to involve a mechanism associated with dislocation loop formation. The martensitic reversion reaction was observed for materials irradiated both by HVEM and by heavy ions. The austenitic precipitates were stable and grew with irradiation at 450°C. They were found to nucleate in all orientations consistent with the Nishiyama-Wassermann relation in the body centered cubic matrix. This paper develops an explanation of this behavior based on dislocation loop morphology and relative phase stability.
Using ASTM D 4065-82 for Predicting Processability and Properties
Authors: Driscoll SB 
Published: December 2008

Recently ASTM D 4065-82 (Practice for Determining and Reporting Dynamic Mechanical Properties of Plastics) was written to provide important rheological information on thermoplastics and thermosetting resins/reinforced plastics-composites. These procedures have been established for monitoring the subtleties of macromolecular behavior, the effects of processing, and in-service performance.
The significance of ASTM D 4065-82 is the generation of important rheological information that can be used to organize, monitor, and provide the necessary information for the quality control and assurance engineer.
Dynamic mechanical testing (DMT) of polymeric material systems provides important viscoelastic information for the materials, design, and process engineer. DMT quickly generates the critical information the materials engineer needs for formulating new composite systems, especially as raw material prices change. The design engineer will use DMT results for optimizing functional performance with greater reliability. The processing engineer will use DMT for assessing the effects of processing parameters on functional performance and determining the effect of changes in temperature on modulus, impact, and dimensional stability.
DMT provides critical information on the effects of the environment, such as moisture on long-term durability. Short-term dynamic mechanical characterizations can be used to establish “master curves” for predicting time-dependent behavior.
Representative examples of DMT as a function of frequency (dynamic oscillation), strain, temperature, and time are cited to illustrate how ASTM D 4065-82 is being used as an effective analytical procedure for ensuring quality and for predicting long-term functional performance. The final section of this paper details the use of instrumented impact testing [ASTM D 3763-79 (Test Method for High-Speed Puncture Properties of Rigid Plastics)] for generating additional information on functional performance.
Effects of Early Heat of Hydration and Exposure to Elevated Temperatures on Properties of Mortars and Pastes with Slag Cement
Authors: Roy DM , White EL , Nakagawa Z 
Published: December 2008

The behavior of slag cements combining substantial amounts of separately ground granulated blast-furnace slag is compared with that of portland cements. The effects on mortars and pastes of exposure to elevated temperatures during early-stage hydration and at later ages has been determined. Compressive strength, density, microstructure, permeability, and dimensional change were the primary properties investigated. The effects of long-term exposure at temperatures up to 250°C were evaluated. Very low permeabilities, &lt;10−8 darcys (μm2), were maintained in most of the mortars. The phase changes with time were determined by X-ray diffraction.
Compressive strengths up to 200 MPa and higher were found in some of the mortars. Pore structures by mercury porosimetry were also investigated, revealing very fine pore structures and some changes with elevated temperature.
Standardization Suggested by the Automated Manufacturing Research Facility (AMRF)—A Research Testbed for the Factory of the Future
Authors: Bloom HM , McLean CR 
Published: December 2008

A research effort has been initiated at the National Bureau of Standards to develop a small batch manufacturing system to support study and experimentation in automated metrology and interface standards for the computer-integrated factory of the future. When completed, the resulting testbed system will be made available for fundamental studies in manufacturing technology by scientists and engineers from government, industry, and universities. This paper will report on the progress of major software and hardware subprojects that are being carried out in support of the construction of the automated manufacturing research facility (AMRF).
The basic approach to the research effort is to take the structure of an automated manufacturing facility and decompose the functional elements in a top-down fashion until the elements are no longer divisible. At this level, systems are defined for robots, machine tools, carts, conveyors, and other similar type units. The project will define the processes that occur at each level, how they can be measured using sensors with software support, and the interface specifications between modules.
Projects will address the applications of (1) hierarchical control techniques to implement the factory-command structure, (2) artificial intelligence/expert systems and decision support systems for work on distributed process planning and scheduling functions, (3) distributed data management systems to handle the problem of a wide spectrum of data requirements, and (4) network communications techniques to manage the various data flow requirements through all levels of the factory system.
Other projects will address the issue of software support systems for an automated system. Graphics interfaces for a manufacturing environment will be developed based on human engineering considerations. Simulation and emulation systems are and will continue to be used for the design and testing of automated systems.
Some projects will address the problem of making the elementary unit, such as robots, more capable of responding to a changing environment. These projects include adding many types of sensors (vision, tactile, force, proximity, etc.) to the robot system to allow for a more sensory interactive real-time control system. A continuing project utilizing sensors on machine tools has demonstrated the ability to improve a machine tool's accuracy. These projects will lead to adaptive control being performed at the equipment level.
Characterization of Crack Closure
Authors: Sehitoglu H 
Published: December 2008

Crack opening and closure levels are determined for small cracks growing from sharp and blunt notches during cyclic loading. Crack tip opening displacement measurements as low as 0.1 μm are reported. Experimental crack opening levels are compared with analytical crack opening levels for various stress intensity ranges, crack lengths, and R-ratios.
The crack growth rate behavior in the vicinity of blunt and sharp notches as well as in smooth specimens is studied. The high crack growth rates observed for small cracks growing from blunt notches are interpreted based on the variation of crack opening level with the crack length. Effective stress intensity range is defined to account for crack closure effects. The crack growth rate correlated well with the effective stress intensity range obtained from sharply and bluntly notched specimens of 1070 steel.
Stress Intensity Factors for Surface Cracks with Arbitrary Shapes in Plates and Shells
Authors: Miyoshi T , Shiratori M , Tanabe O 
Published: December 2008

In order to analyze stress intensity factors for surface cracks with arbitrary shapes in plates and shells, the authors have developed a new finite element scheme based upon the line spring model. In this scheme Ahmad's thick shell elements are combined with the newly developed line spring elements with quadratic shape functions. This line spring method has more potential of application than a previously reported method where flat shell elements were combined with the line spring elements with linear shape functions.
In the analysis of K-values for a single semielliptical surface crack in tension, it has been found that the method has nearly the same accuracy as the three-dimensional finite element method, while the computing time is one order of magnitude less. The method has been applied to the problem of interaction of twin semielliptical cracks in tension. The estimation scheme for K-values by ASME Boiler and Pressure Vessel Code has been found to give conservative K-values for most of the separated twin cracks, except for very deep cracks. For overlapping twin cracks, K-values at the intersecting points become very large; for example, the highest value is about three times larger than the maximum value for a single crack with the same size as one of the twin cracks. Therefore caution must be used in dealing with these cracks.
Single rectangular and triangular cracks have been analyzed. It has been found that the ASME Code gives conservative K-values for triangular cracks but underestimates values for rectangular cracks.
Current Understanding of the Mechanisms of Stress Corrosion and Corrosion Fatigue
Authors: Ford FP 
Published: December 2008

Failure of components operating in various environments due to cracking remains a safety and economic problem despite the effort that has been devoted to understanding the phenomena of stress corrosion, hydrogen embrittlement, and corrosion fatigue. This article reviews our current understanding of the mechanisms of stress corrosion and corrosion fatigue in ductile alloy/aqueous environment systems, with emphasis placed on the application of this mechanistic knowledge to the formulation of remedial actions, design criteria, and relevant testing techniques.
It is concluded that many of the recent arguments associated with, for example, the applicability of the slip-dissolution or hydrogen-embrittlement mechanisms of crack advancement under static and dynamic loading conditions may be of minor importance from a practical view, since the same rate-determining steps in crack propagation can operate in these mechanisms and modes of cracking. Bearing in mind that crack advance in ductile structural-alloy/aqueous-environment systems is primarily an electrochemically related process, our understanding of the cracking mechanism suggests that, at a given potential, the propagation rate is controlled by reaction rates (for example, dissolution, hydrogen-ion reduction) on the crack tip and sides and how these are affected by the passivation rate, liquid diffusion rate, and strain rate at or near the crack tip. Knowledge of the interactions between these controlling processes leads to a quantitative understanding of the spectrum of behavior between stress corrosion and corrosion fatigue and of the criteria that dictate whether crack propagation will arrest or accelerate.
Computer-Controlled Fatigue Crack Growth Rate Testing on Bend Bars in a Corrosive Environment
Authors: Fabis TR , Liaw PK , Ceschini LJ , Leax TR , Landes JD 
Published: December 2008

Automated fatigue crack growth experiments were conducted on a 304 stainless steel in air and wet hydrogen at 654 kPa. The tests were performed using three-point bend specimens in the frequency range from 0.1 to 10 Hz.
Results show that the fatigue crack propagation rate in the hydrogen gas environment can increase with decreasing frequency. For ΔK-values higher than 22 MPam, the crack growth rate data in wet hydrogen at 10 Hz are 40% higher than those encountered in the ambient environment. The crack growth rates developed in the constant ΔK tests are in good agreement with those in the decreasing and increasing ΔK tests in both air and wet hydrogen environments.