An analytical and experimental study of crack extension in center-notched composites

The normal stress ratio theory for crack extension in anisotropic materials is studied analytically and experimentally. The theory is applied within a microscopic-level analysis of a single center notch of arbitrary orientation in a unidirectional composite material. The bulk of the analytical work of this study applies an elasticity solution for an infinite plate with a center line to obtain critical stress and crack growth direction predictions. An elasticity solution for an infinite plate with a center elliptical flaw is also used to obtain qualitative predictions of the location of crack initiation on the border of a rounded notch tip. The analytical portion of the study includes the formulation of a new crack growth theory that includes local shear stress. Normal stress ratio theory predictions are obtained for notched unidirectional tensile coupons and unidirectional Iosipescu shear specimens. These predictions are subsequently compared to experimental results

Space spider crane

A space spider crane for the movement, placement, and or assembly of various components on or in the vicinity of a space structure is described. As permanent space structures are utilized by the space program, a means will be required to transport cargo and perform various repair tasks. A space spider crane comprising a small central body with attached manipulators and legs fulfills this requirement. The manipulators may be equipped with constant pressure gripping end effectors or tools to accomplish various repair tasks. The legs are also equipped with constant pressure gripping end effectors to grip the space structure. Control of the space spider crane may be achieved either by computer software or a remotely situated human operator, who maintains visual contact via television cameras mounted on the space spider crane. One possible walking program consists of a parallel motion walking program whereby the small central body alternatively leans forward and backward relative to end effectors

Lack of Brown-Headed Cowbird Nest Parasitism in a Short Grass Region

While conducting field work in Morton County, southwestern Kansas and Baca County, southeastern Colorado, during the period 27 May to 2 July 1997, we found 36 nests of seven bird species. Nests were not searched for systematically, but were found coincidentally as data were collected along transects during research investigating the breeding bird and plant communities of black-tailed prairie dog (Cynomys ludovicianus) colonies and noncolonized shortgrass prairie (Winter 1999). Low densities of the brown-headed cowbird in our study region, which is characterized by a semi-arid climate, might be a consequence of host populations that exhibit extreme temporal and spatial variability in response to the climatic variability of these regions (Wiens 1974, Cody 1985, Winter et al. 2003). As host populations vary greatly in time and space over large areas on the western Great Plains (Wiens 1974, Cody 1985), perhaps the brown-headed cowbird is simply unable to effectively respond to host population changes

An Archaeological Survey of Randleman and Howard Mills Reservoirs

A miscellaneous report by the Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. These reports discuss the findings of archaeological survey, testing, and excavations undertaken by the RLA between 1973 and 1985

1974 Excavations Within the New Hope Reservoir

A miscellaneous report by the Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. These reports discuss the findings of archaeological survey, testing, and excavations undertaken by the RLA between 1973 and 1985

Ultrasonics Guided Waves for Piping Inspection

An ultrasonic guided wave system for pipe inspection is proposed. Using guided wave experience to date on a variety of different tubing problems, feasibility experiments have already been conducted on piping under insulation in both a laboratory and chemical processing facility field environment. Several guided wave techniques are introduced, one using a broad banded variable angle beam transducer on a curved shoe, and one on a newly developed pipe comb system. Discussion on both axisymmetric and non-axisymmetric wave propagation is presented

Market forces determine media coverage of death penalty decisions by state high courts

What determines how death penalty cases are covered by the media? In new research, Richard L. Vining, Jr., Teena Wilhelm and Jack D. Collens argue that the press does not treat all cases equally, and that they are more likely to report on cases that will have broad appeal and increase their sales and profits. They find that a newspaper is nearly 60 percent more likely to cover a death penalty case decision if the offender is a woman and about 30 percent more likely if the sentence or conviction is overridden

TB117: Techniques for Using the Growth and Behavior of Imprinted Ducklings to Evaluate Habitat Quality

We developed a technique for evaluating duckling habitat quality that is based on two assumptions. In good habitat young birds (1) grow rapidly and thus are better able t o survive stresses such as inclement weather, and (2) spend relatively less time moving about in search of food and more time resting and thus are less conspicuous to predators. We imprinted artificially incubated and hatched ducklings by being present at the time of hatching; i.e., the ducklings thought we were their mother. Ducklings were split into broods and placed on ponds where their growth was measured and their behavior monitored for several days. Comparisons of growth rates and behavioral time budgets allowed us to determine which ponds were better habitat. This paper describes techniques for imprinting, duckling husbandry, and measurement of growth and behavior.https://digitalcommons.library.umaine.edu/aes_techbulletin/1077/thumbnail.jp