Study of high resolution wind measuring systems. phase i survey, july through september 1964

High resolution wind measuring systems using probes, tracers, and sound technique

Melt infiltration casting of bulk metallic-glass matrix composites

The authors describe a technique for melt infiltration casting of composites with a metallic-glass matrix. We made rods 5 cm in length and 7 mm in diameter. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed composites were those reinforced with tungsten and carbon steel continuous wire reinforcement. The Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 matrix was quenched to a glass after infiltrating the reinforcement. We analyzed the microstructure of the composites by x-ray diffraction and scanning electron microscopy. The measured porosity was less than 3% and the matrix was about 97% amorphous material

Mechanical properties of Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6) metallic glass matrix particulate composites

To increase the toughness of a metallic glass with the nominal composition Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6), it was used as the matrix in particulate composites reinforced with W, WC, Ta, and SiC. The composites were tested in compression and tension experiments. Compressive strain to failure increased by more than 300% compared with the unreinforced Zr_(57)Nb_5Al_(10)Cu_(15.4)Ni_(12.6), and energy to break of the tensile samples increased by more than 50%. The increase in toughness came from the particles restricting shear band propagation, promoting the generation of multiple shear bands and additional fracture surface area. There was direct evidence of viscous flow of the metallic glass matrix within the confines of the shear bands

Shear bands and cracking of metallic glass plates in bending

The thickness dependence of yielding and fracture of metallic glass plates subjected to bending is considered in terms of the shear band processes responsible for these properties. We argue that the shear band spacing (and length) scales with the thickness of the plate because of strain relaxation in the vicinity of the shear band at the surface. This is consistent with recent measurements of shear band spacing versus sample size. We also argue that the shear displacements in the shear band scale with the shear band length and plate thickness, thus causing cracks to be initiated in thicker plates at smaller bending strains. This leads to fracture bending strains that decrease markedly with increasing plate thickness, consistent with recent experiments. These results suggest that amorphous metals in the form of foams might have superior ductility and toughness

Relationships Between Habitat and Snag Characteristics and the Reproductive Success of the Brown-headed Nuthatch (Sitta pusilla) in Eastern Texas.

Habitat use and reproductive success of the Brown-headed Nuthatch (Sitta pusilla Latham) were studied in East Texas during the 2001-2002 breeding seasons. We compared nest cavity selection at used and randomly selected non-used areas. Height of nest trees, midstory density, and percent leaf litter were negatively correlated with nest site selection. Brown-headed Nuthatches showed a strong preference for short snags; yet placed their nest cavity entrances near the top ofthe snags. While nuthatches may be selecting for habitats with little or no midstory density, percent of leaf litter in the nest sites is most likely the consequence of frequent burning. No significant differences among habitat variables and snag characteristics were found between successful and failed nest cavities. Additionally, no habitat variables were correlated with the number of chicks fledged per nest. Predation was the major cause of nest failure in this study

Why some tribal governments are more likely to partner with state and local law enforcement than others.

In many respects, Indian lands in the US can be considered to be a country within a country. With many tribal governments having their own law enforcement agencies there is a risk of jurisdictional conflict with agencies outside of Indian Country. Thaddieus W. Conner and Stephanie L. Witt take a close look at cross-deputization agreements between law enforcement agencies which allow officers from tribal, state, and local agencies to actively respond to issues regardless of jurisdictional boundaries. They find that the major determinants of such cooperation are the presence of Indian gaming, higher rates of violent crime, as well as organizational resources and capacity

Growth and Survival of Baldcypress Planted in an Old Ricefield of Coastal South Carolina

Vast acreages of baldcypress [Taxodium distichum (L.) Rich.] swampland in coastal South Carolina were cleared for rice production starting in the late 1600s. When rice cultivation ended in the late 1800s, many cultivated areas becamemarshlands. Other fields failed to return to forest unless they were planted. In one such area, nine acres were planted with baldcypress in 1956 by MeadWestvaco near Walterboro, SC. Seedlings were planted on an 8- by 8-foot spacing. Beginning in November 1991, five 0.12-acre plots were established within the stand to monitor tree growth and survival and measured yearly. In addition to baldcypress, the stand now contains red maple (Acer rubrum L.), black willow (Salix nigra Marsh.), sweetgum (Liquidambar styraciflua L.), and persimmon (Diospyros virginiana L.). The number of trees per acre declined from 600 to 402 by year 2000. Average diameter of trees after 44 years was 9.1 inches. In 2001, MeadWestvaco clearcut half of the stand, thinned 1/4 of the stand, and left 1/4 intact. All stems were removed from the clearcut section, and the thinned section was reduced to 104 stems per acre (88 percent of remaining trees are baldcypress). Five regeneration plots were placed in the clearcut area to follow future regeneration patterns