Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transition temperature

The intermetallic compound NiAl is one of many advanced materials which is being scrutinized for possible use in high temperature, structural applications. Stoichiometric NiAl has a high melting temperature, excellent oxidation resistance, and good thermal conductivity. Past research has concentrated on improving monotonic properties. The encouraging results obtained on binary and micro-alloyed NiAl over the past ten years have led to the broadening of NiAl experimental programs. The purpose of this research project was to determine the low cycle fatigue properties and dislocation mechanisms of stoichiometric NiAl at temperatures near the monotonic brittle-to-ductile transition. The fatigue properties were found to change only slightly in the temperature range of 600 to 700 K; a temperature range over which monotonic ductility and fracture strength increase markedly. The shape of the cyclic hardening curves coincided with the changes observed in the dislocation structures. The evolution of dislocation structures did not appear to change with temperature

Tables of square-law signal detection statistics for Hann spectra with 50 percent overlap

The Search for Extraterrestrial Intelligence, currently being planned by NASA, will require that an enormous amount of data be analyzed in real time by special purpose hardware. It is expected that overlapped Hann data windows will play an important role in this analysis. In order to understand the statistical implication of this approach, it has been necessary to compute detection statistics for overlapped Hann spectra. Tables of signal detection statistics are given for false alarm rates from 10(exp -14) to 10(exp -1) and signal detection probabilities from 0.50 to 0.99; the number of computed spectra ranges from 4 to 2000

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process

Complex examination of the Upper Paleozoic siliciclastic rocks from southern Transdanubia, SW Hungary—Mineralogical, petrographic, and geochemical study

A vertical section of Upper Paleozoic sandstones from southern Transdanubia (Mecsek-Villány area, Tisza mega-unit, Hungary) has been analyzed for major and trace elements, including rare earth elements (REEs). In addition, the clay mineralogy of the sandstone samples and the petrography and geochemistry of gneiss and granitoid clasts extracted from the associated conglomerates have been determined. Geochemistry of the sandstone samples analyzed in this study shows that these rocks were predominantly derived from a felsic continental source; nevertheless, compositions vary systematically up-section. The Pennsylvanian (Upper Carboniferous) Téseny Formation has higher SiO(2) and lower Na(2)O, CaO, Sr, high field strength element (HFSE), and ΣREE contents relative to the Permian strata. Its high K(2)O and Rb contents together with the presence of abundant illite-sericite suggest a potassium metasomatism in this formation. Clay mineralogy and large ion lithophile element (LILE) contents of the Lower Permian Korpád Formation vary spatially and are interpreted as local variations in composition of the source region and postdepositional conditions. Zr and Hf abundances and REE patterns, however, show that this formation was derived from mature upper continental crust. The Upper Permian Cserdi Formation has higher TiO(2), Th, U, Y, Cr, and heavy (H) REE contents, and higher Cr/Th and Cr/Zr ratios relative to the underlying formations. These trends can be explained by a sedimentary system dominated by highly weathered detritus derived from combined recycled-orogen, basement-uplift, and volcanic-arc provenance in the Téseny Formation, with an increased proportion of less weathered detritus derived from combined volcanic and basement-uplift provenances in the Permian formations. Characteristics of the Cserdi unit may reflect relatively proximal derivation from a felsic volcanic source

Normal and abnormal tissue identification system and method for medical images such as digital mammograms

A system and method for analyzing a medical image to determine whether an abnormality is present, for example, in digital mammograms, includes the application of a wavelet expansion to a raw image to obtain subspace images of varying resolution. At least one subspace image is selected that has a resolution commensurate with a desired predetermined detection resolution range. A functional form of a probability distribution function is determined for each selected subspace image, and an optimal statistical normal image region test is determined for each selected subspace image. A threshold level for the probability distribution function is established from the optimal statistical normal image region test for each selected subspace image. A region size comprising at least one sector is defined, and an output image is created that includes a combination of all regions for each selected subspace image. Each region has a first value when the region intensity level is above the threshold and a second value when the region intensity level is below the threshold. This permits the localization of a potential abnormality within the image

(SNP037) Claud Cullers interviewed by Dorothy Noble Smith, transcribed by Sharon G. Marston

Records the reminiscences of Claud W. Cullers, a lifelong resident of Rileyville, Virginia, who raised cattle throughout the 1920s and 1930s. Mr. Cullers would move his cattle to mountain pastures each year, where they would graze into the fall. Describes his memories of the local mountain people, their modes of living and sources of income. Discusses the bark and lumber industries, chestnut, apple and berry harvests, and prominent local moonshiners. A woman with the surname Keyser, identified as Mrs. Cullers\u27 niece, also contributes to the interview.https://commons.lib.jmu.edu/snp/1027/thumbnail.jp

Mineralogical and Chemical Evolution of Lamproites in Woodson and Wilson Counties, Southeastern Kansas

The major and trace element content of 123 lamproites and associated sedimentary rock samples from six cores of the Silver City Dome and two cores from the Rose Dome in southeastern Kansas were analyzed. The lamproites are ultrapotassic (weight percent K2O/Na2O = 2.0 to 22.1), alkalic (molecular [K2O +Na2O]/Al2O3 = 1.01 to 3.04), and are enriched in mantle-incompatible elements (e.g., light REE, Ta, Hf, Ba, Rb, Sr, Th). The low Al2O3 content of these samples is consistent with lamproites formed in stable continental settings such as those from West Kimberley, Australia, and Smoky Butte, Montana. Also the lack of a significant negative Ta and Nb anomaly in mantle-normalized plots precludes the source rocks having been involved in subduction. The samples from the Silver City cores are composed of mostly serpentinized olivine and mica with lesser amounts of K-richterite, diopside, rutile, apatite, perovskite, and spinel in a serpentinized groundmass. The Rose Dome cores contain mostly serpentinized olivine and mica with minor diopside, spinel, perovskite (more abundant than at Rose Dome), xenotime, and feldspar. Most mica compositions follow the trend of decreasing FeO and Al2O3 similar to trends of the Guess Core and the Wolgidite trend at West Kimberly. Micas enriched in Ba and Ti (BaO = 16.6–19.3 weight percent; TiO2 = 26.0– 27.8 weight percent) rim some micas of more normal composition. These very high Ba and Ti-rich micas have not been found in other lamproites or other types of alkalic rocks. The average composition of the shallow cores at the Silver City Dome are similar to one another (except for Na2O, Li, and Cs), although the average composition of the shallow cores are different than the previously studied deeper Guess and Ecco Ranch cores in this area. The average composition of the two Eagle cores at Rose Dome are similar to one another, but they are higher in Fe2O3 (total), MgO, CaO, P2O5, Th, Co, Ni, Cr, U, Y, REE, Cu, and Cs concentrations than the shallow cores from the Silver City Dome. Metasomatized mantle (lherzolite-harzburgite) containing varied amounts of veins containing clinopyroxene, K-Ti amphibole, phlogopite, apatite, and K-Ba-Zr-Nb titanates could have melted in varied amounts to form the lamproites. The lower SiO2 and Al2O3 and higher MgO lamproites at Rose Dome likely result from melting at a higher temperature of more lherzolite-harzburgite and less vein material than the more SiO2-rich and MgO-poor lamproites at Silver City. Also the concentration of most elements varies vertically in the cores, and the variation in the elemental concentration can be related to mineral gravity settling, flow differentiation, or volatile transport processes within the sills. For example, at the Silver City Dome, concentrations of olivine and phlogopite can be related to the samples with the lowest SiO2 and highest MgO, Mg#, Ni, and Co content. The portions of the cores with the highest concentrations of K2O, Al2O3, and Sc may be correlated to samples with the highest phlogopite. Also Ba often decreases in amount upward in many cores at the Silver City Dome and is enriched in overlying hornfels compared to the unaltered overlying shale. Ba movement in H2O-rich fluids into the overlying hornfels can explain this observation. Curiously, overlying limestones are not enriched in Ba, so at least locally the limestones may be impervious to the fluids