Composite components on commercial aircraft

Commercial aircraft manufacturers are making production commitments to composite structure for future aircraft and modifications to current production aircraft. Flight service programs with advanced composites sponsored by NASA during the past 10 years are described. Approximately 2.5 million total composite component flight hours have been accumulated since 1970 on both commercial transports and helicopters. Design concepts with significant mass savings were developed, appropriate inspection and maintenance procedures were established, and satisfactory service was achieved for the various composite components. A major NASA/U.S. industry technology program to reduce fuel consumption of commercial transport aircraft through the use of advanced composites was undertaken. Ground and flight environmental effects on the composite materials used in the flight service programs supplement the flight service evaluation

Worldwide flight and ground-based exposure of composite materials

The long-term durability of those advanced composite materials which are applicable to aircraft structures was discussed. The composite components of various military and commercial aircraft and helicopters were reviewed. Both ground exposure and flight service were assessed in terms of their impact upon composite structure durability. The ACEE Program is mentioned briefly

Buckling of conical shell with local imperfections

Small geometric imperfections in thin-walled shell structures can cause large reductions in buckling strength. Most imperfections found in structures are neither axisymmetric nor have the shape of buckling modes but rather occur locally. This report presents the results of a study of the effect of local imperfections on the critical buckling load of a specific axially compressed thin-walled conical shell. The buckling calculations were performed by using a two-dimensional shell analysis program referred to as the STAGS (Structural Analysis of General Shells) computer code, which has no axisymmetry restrictions. Results show that the buckling load found from a bifurcation buckling analysis is highly dependent on the circumferential arc length of the imperfection type studied. As the circumferential arc length of the imperfection is increased, a reduction of up to 50 percent of the critical load of the perfect shell can occur. The buckling load of the cone with an axisymmetric imperfections is nearly equal to the buckling load of imperfections which extended 60 deg or more around the circumference, but would give a highly conservative estimate of the buckling load of a shell with an imperfection of a more local nature

Aberrational Effects for Shadows of Black Holes

In this paper, we discuss how the shadow of a Kerr black hole depends on the motion of the observer. In particular, we derive an analytical formula for the boundary curve of the shadow for an observer moving with given four-velocity at given Boyer--Lindquist coordinates. We visualize the shadow for various values of parameters.Comment: 12 pages, 3 figures; Proceedings of the 524. WE-Heraeus-Seminar held at the Physikzentrum, Bad Honnef, Germany, 17.--23.2.201

Bullying Victimization and Perpetration: Some Answers and More Questions

The U.S. government has defined bullying victimization as “any unwanted aggressive behavior(s) by another youth or group of youths who are not siblings or current dating partners that involves an observed or perceived power imbalance and is repeated multiple times or is highly likely to be repeated”.1 Conceptualizations of bullying and the use of the term vary by audience and context. For instance, for some, bullying behaviors might include acts of aggression or violence, whereas for others bullying might center on name-calling, exclusionary social practices or even spreading rumors and vicious lies.

Community Violence Exposure and Sexual Behaviors in a Nationally Representative Sample of Young Adults: The Effects of Race/Ethnicity and Gender

This study examined whether exposure to community violence was related to sexual risk behaviors in a nationally representative sample of young adults and if there were gender or racial/ethnic differences in these relationships. The analytic sample for this study was drawn from the National Longitudinal Study of Adolescent Health and was composed of 7,726 unmarried, heterosexual African American, Caucasian, and Hispanic/Latino young adults aged 18 to 27 years old. Approximately 12% of participants reported some community violence exposures, with men and African Americans reporting the highest rates of such exposures. Regression analyses controlling for age, gender, parental education, and family structure indicated that exposures to community violence were associated with earlier sexual debut history, a higher number of sexual partners within the previous 12 months, and a higher number of total sexual partners. Additionally, violence exposures had stronger effects for males and weaker effects for African Americans. Primary and secondary sexual risk prevention initiatives would need to consider how patterns of sexual risk behaviors may be related to exposure to community violence and how such relationships may differ based on gender and race/ethnicity. Future research should also seek to illuminate pathways connecting these 2 major public health concerns

Event-based knowledge elicitation of operating room management decision-making using scenarios adapted from information systems data

<p>Abstract</p> <p>Background</p> <p>No systematic process has previously been described for a needs assessment that identifies the operating room (OR) management decisions made by the anesthesiologists and nurse managers at a facility that do not maximize the efficiency of use of OR time. We evaluated whether event-based knowledge elicitation can be used practically for rapid assessment of OR management decision-making at facilities, whether scenarios can be adapted automatically from information systems data, and the usefulness of the approach.</p> <p>Methods</p> <p>A process of event-based knowledge elicitation was developed to assess OR management decision-making that may reduce the efficiency of use of OR time. Hypothetical scenarios addressing every OR management decision influencing OR efficiency were created from published examples. Scenarios are adapted, so that cues about conditions are accurate and appropriate for each facility (e.g., if OR 1 is used as an example in a scenario, the listed procedure is a type of procedure performed at the facility in OR 1). Adaptation is performed automatically using the facility's OR information system or anesthesia information management system (AIMS) data for most scenarios (43 of 45). Performing the needs assessment takes approximately 1 hour of local managers' time while they decide if their decisions are consistent with the described scenarios. A table of contents of the indexed scenarios is created automatically, providing a simple version of problem solving using case-based reasoning. For example, a new OR manager wanting to know the best way to decide whether to move a case can look in the chapter on "Moving Cases on the Day of Surgery" to find a scenario that describes the situation being encountered.</p> <p>Results</p> <p>Scenarios have been adapted and used at 22 hospitals. Few changes in decisions were needed to increase the efficiency of use of OR time. The few changes were heterogeneous among hospitals, showing the usefulness of individualized assessments.</p> <p>Conclusions</p> <p>Our technical advance is the development and use of automated event-based knowledge elicitation to identify suboptimal OR management decisions that decrease the efficiency of use of OR time. The adapted scenarios can be used in future decision-making.</p

A Descriptive Study on the Preparation of Student Teachers to Work with Diverse Populations

If the agricultural education profession is to attract a more diverse audience to pursue agriculture as a viable career path, the secondary teacher education pathway must be reevaluated. The purpose of the study was to describe the degree to which the involved agricultural education programs prepared their students to work with diverse populations. The study also examined attitudes and beliefs of the student teachers regarding diversity. The results of the study suggest that this group of student teachers was not adequately exposed to diversity neither in their student teaching experience nor in their university preparation. To assist the national agricultural education goal of diversity in agriculture, a national study should be conducted to determine if there is a correlation between minority enrollment in agriculture and the race and gender of the teacher educator

Development of Stitched, Braided and Woven Composite Structures in the ACT Program and at Langley Research Center (1985 to 1997) Summary and Bibliography

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 NASA Langley Research in Textile Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Advanced Material Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Woven Preforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Multiaxial Knitted Preforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Braided Preforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

Compressive properties and column efficiency of metals reinforced on the surface with bonded filaments

Compressive properties and weight saving of metals reinforced on surface with resin bonded fiber