Structural efficiency study of composite wing rib structures

A series of short stiffened panel designs which may be applied to a preliminary design assessment of an aircraft wing rib is presented. The computer program PASCO is used as the primary design and analysis tool to assess the structural efficiency and geometry of a tailored corrugated panel, a corrugated panel with a continuous laminate, a hat stiffened panel, a blade stiffened panel, and an unstiffened flat plate. To correct some of the shortcomings in the PASCO analysis when shear is present, a two step iterative process using the computer program VICON is used. The loadings considered include combinations of axial compression, shear, and lateral pressure. The loading ranges considered are broad enough such that the designs presented may be applied to other stiffened panel applications. An assessment is made of laminate variations, increased spacing, and nonoptimum geometric variations, including a beaded panel, on the design of the panels

IT\u27S ABOUT MORE THAN JUST ANIMALS : ENVIRONMENTAL POLITICS OF ZOO-ADJACENT CONSERVATION(ISTS) IN THE U.S.

This research explores the influences of diverse environmental politics in shaping zoo-adjacent conservation activities in the United States. Based upon 13 months of multi-sited ethnographic research, conducted with conservation actors across six states, the researcher investigates and documents how conservation professionals—operating in contexts adjacent to zoological institutions—experience and respond to the socio-environmental implications associated with the cascading effects of global environmental change. In the face of current challenges and uncertain environmental futures—shaped by habitat alterations, ecological transitions, and species declines/extinctions—conservationists are undergoing their own processes of reassessment and reconfiguration of their underpinning philosophies and body of practices that inform their relationships to the environment. The research lays out an argument about how in the face of socio-environmental change, conservation—and the ongoing reconfigurations of its identities, priorities, and practices—are being shaped by conservation organizations and individual conservation actors across scales of influence; from powerful organizations and their executives, to on-the-ground professionals doing the day-to-day work of conservation programs. This represents a contribution to understandings of how ‘Conservation’ comes into being, which, in the literature, is often treated as a monolithic entity and is absent of the contextualized realities of conservation organizations and the individuals who comprise them. Centering examinations of those contextualized realities that shape how conservation comes into being across scales, this research examines: how zoological institutions are increasingly foregrounding narratives about their identities as “conservation organizations”; how professionals are grappling with their shifting understandings of ‘nature’ and the role of conservation interventions therein; increasing interventionist approaches and related connections between on-the-ground professionals and species of concern; the impact of scientific knowledge politics on conservation activities; and the webs of social relations involved in enacting contemporary conservation actions. Ultimately, this research understands Conservation—a diverse body of philosophies and praxis—as an arena of human-environmental relation(s) that must be examined across scales of influence and through the contextualized realities of individual actors and organizations who comprise it. Moving beyond traditions of monolithic treatment, this project contributes to scholarly work involved in developing a more “multifaceted understanding” of conservation activities through attention to the experiences and “complex realities” of conservation professionals

The effect of impact damage and circular holes on the compressive strength of a graphite-epoxy laminate

Specimens were impacted by 1.27-cm-diameter aluminum spheres with speeds ranging from 52 to 101 m/s. Some specimens were impacted without any applied compressive load and then loaded to failure to determine their residual strength. Other specimens were loaded to a prescribed axial compressive strain and impacted while at that applied load. Loaded specimens that did not fail catastrophically on impact were subsequently loaded to failure to determine their residual strength. Low-velocity impact damage was found to degrade seriously the laminate static compressive strength. Low-strain compression-compression cyclic loading was found to degrade further the compressive strength of impact-damaged specimens. Specimens with circular holes having diameters up to a third of the specimen width were loaded to failure in compression. It was found that circular holes can also degrade the static compressive strength of the laminate. The effects of circular holes and impact damage on the compressive strength of the laminate are compared

Effect of Low Velocity Impact Damage on the Compressive Strength of Graphite/Epoxy Hat-Stiffened Panels

Low velocity impact damage on the compressive strength of graphite/epoxy hat stiffened panels is studied. Fourteen panels, representative of minimum-mass designs for two compression load levels were tested. Eight panels were damaged by impact and the effect on compressive strength was evaluated by comparing the results with data for undamaged panels. The impact tests consisted of firing 1.27 cm diameter aluminum projectiles normal to the plane of the panel at a velocity of approximately 55 m/sec to simulate impact from runway debris. The results of this investigation indicate that impact damage in the panels designed for 0.53 MN/m was contained locally and the damaged panels were capable of carrying the design load. The panels designed for 1.58 MN/m failed between 50 and 58 percent of the design load due to impact damage in the high axial stiffness region. The extent of damage in the high axial stiffness region of both panel designs increased with the magnitude of applied axial load. Damage in this region was the most significant factor in reducing panel strength. Limited damage that was not visually detectable reduced ultimate strength as much as extensive visible damage

A two year educational curriculum for para-professional planning technicians

Call number: LD2668 .P7 1973 S7

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described

Cubane Tetrameric Complexes of Copper(I) Chloride and Bromide with Triphenyl Phosphite

The crystal structures of tetra-/z3-chloro-tetrakis[(triphenyl phosphite-P)copper(I)], [CunC14(CI8HI503P)4], and tetra-#3-bromo-tetrakis [ (triphenyl phosphite-P) - copper(I)], [Cu4Br4(CI8H1503P)4], are described. Both have distorted \u27cubane\u27 CuaX4 cores. Distortion of the cubane structure is reflected in X--Cu--X angles \u3e 90 ° and Cu--X--Cu angles \u3c 90 °, and is more pronounced in the bromide complex

Aberrant right subclavian artery syndrome: A case of chronic cough1 1Competition of interest: none.

AbstractA young, otherwise healthy man had chronic cough of 16 months’ duration. Evaluation revealed an aberrant right subclavian artery. Kommerell’s diverticulum without aneurysmal degeneration was present. Imaging studies showed compression of the esophagus but not the trachea. Results of methacholine challenge test were negative for evidence of reactive airway disease, but suggested mild variable intrathoracic obstruction. While aberrant right subclavian artery syndrome most commonly involves dysphagia, our patient’s only symptom was cough. Right subclavian artery to right common carotid artery transposition was performed, with oversewing of the subclavian artery stump to the left of the esophagus through a right supraclavicular incision. This treatment was curative, with complete resolution of symptoms

Early Onset of Franciscan Subduction

The Franciscan subduction complex of California is considered a type example of a subduction-accretion system, yet the age of subduction initiation and relationship to the tectonic history of western North America remain controversial. Estimates for the timing of Franciscan subduction initiation are largely based either indirectly on regional tectonic arguments or from the ages of high-grade blocks within mélange. Many of the high-grade blocks record counterclockwise pressure-temperature paths with early amphibolite overprinted by later eclogite and blueschist; however, their origin and significance with respect to subduction initiation have been debated. In contrast, some high-grade blocks show evidence for clockwise pressure-temperature paths and an early eclogite assemblage overprinted by later amphibolite Zircon U-Pb ages from inclusions in garnet and Lu-Hf estimates of initial garnet growth ages from these samples record early eclogite metamorphism at ~176 Ma. Matrix zircon U-Pb ages and Lu-Hf estimates of final garnet growth ages record a barroisite-amphibolite assemblage overprint of eclogite at ~160 Ma. Combined with petrologic data and existing geochronology, the data suggest that (1) Franciscan subduction was underway by no later than 180 Ma, (2) continuous subduction metamorphism occurred for at least 100 Ma, and (3) Franciscan subduction initiation predated the formation of the overlying Coast Range Ophiolite, supporting models that form the ophiolite above an east dipping Franciscan subduction zone