4,813 research outputs found
Study of metallic structural design concepts for an arrow wing supersonic cruise configuration
A structural design study was made, to assess the relative merits of various metallic structural concepts and materials for an advanced supersonic aircraft cruising at Mach 2.7. Preliminary studies were made to ensure compliance of the configuration with general design criteria, integrate the propulsion system with the airframe, select structural concepts and materials, and define an efficient structural arrangement. An advanced computerized structural design system was used, in conjunction with a relatively large, complex finite element model, for detailed analysis and sizing of structural members to satisfy strength and flutter criteria. A baseline aircraft design was developed for assessment of current technology. Criteria, analysis methods, and results are presented. The effect on design methods of using the computerized structural design system was appraised, and recommendations are presented concerning further development of design tools, development of materials and structural concepts, and research on basic technology
Study of advanced composite structural design concepts for an arrow wing supersonic cruise configuration
Based on estimated graphite and boron fiber properties, allowable stresses and strains were established for advanced composite materials. Stiffened panel and conventional sandwich panel concepts were designed and analyzed, using graphite/polyimide and boron/polyimide materials. The conventional sandwich panel was elected as the structural concept for the modified wing structure. Upper and lower surface panels of the arrow wing structure were then redesigned, using high strength graphite/polyimide sandwich panels, retaining the titanium spars and ribs from the prior study. The ATLAS integrated analysis and design system was used for stress analysis and automated resizing of surface panels. Flutter analysis of the hybrid structure showed a significant decrease in flutter speed relative to the titanium wing design. The flutter speed was increased to that of the titanium design by selective increase in laminate thickness and by using graphite fibers with properties intermediate between high strength and high modulus values
MINNESOTA'S LIVESTOCK INDUSTRIES: PAST, PRESENT AND FUTURE STRUCTURAL CHANGE
Livestock Production/Industries,
PROJECTED CONSUMPTION OF LIVESTOCK PRODUCTS
The U.S. consumption pattern of livestock products has changed considerably and is expected to keep changing. The first part of this paper reviews the consumption trends and the price and nonprice factors affecting those trends. In the second part, future consumption patterns are projected. The projections of the constant income elasticity model and the Tornquist functions are rejected due to recent trends which do not receive enough weight in these models. A third model which projects consumption shares is selected as a more accurate predictor. By the year 2010, national consumption of beef is estimated to decrease by 5 to 10%; pork to increase by up to 5%. Lamb and mutton will continue to be consumed less. Poultry consumption will increase dramatically while egg consumption will decrease.Food Consumption/Nutrition/Food Safety, Livestock Production/Industries,
Spontaneous and Stimulated Raman Scattering near Metal Nanostructures in the Ultrafast, High-Intensity regime
The inclusion of atomic inversion in Raman scattering can significantly alter
field dynamics in plasmonic settings. Our calculations show that large local
fields and femtosecond pulses combine to yield: (i) population inversion within
hot spots; (ii) gain saturation; and (iii) conversion efficiencies
characterized by a switch-like transition to the stimulated regime that spans
twelve orders of magnitude. While in Raman scattering atomic inversion is
usually neglected, we demonstrate that in some circumstances full accounting of
the dynamics of the Bloch vector is required
Protocol for a longitudinal qualitative interview study: maintaining psychological well-being in advanced cancer - what can we learn from patients' and carers' own coping strategies?
IntroductionPeople with advanced cancer and their carers experience stress and uncertainty which affects the quality of life and physical and mental health. This study aims to understand how patients and carers recover or maintain psychological well-being by exploring the strategies employed to self-manage stress and uncertainty.Methods and analysisA longitudinal qualitative interview approach with 30 patients with advanced cancer and 30 associated family or informal carers allows the exploration of contexts, mechanisms and outcomes at an individual level. Two interviews, 4–12?weeks apart, will not only enable the exploration of individuals’ evolving coping strategies in response to changing contexts but also how patients’ and carers’ strategies inter-relate. Patient and Carer focus groups will then consider how the findings may be used in developing an intervention. Recruiting through two major tertiary cancer centres in the North West and using deliberately broad and inclusive criteria will enable the sample to capture demographic and experiential breadth.Ethics and disseminationThe research team will draw on their considerable experience to ensure that the study is sensitive to a patient and carer group, which may be considered vulnerable but still values being able to contribute its views. Public and patient involvement (PPI) is integral to the design and is evidenced by: a research advisory group incorporating patient and carers, prestudy consultations with the PPI group at one of the study sites and a user as the named applicant. The study team will use multiple methods to disseminate the findings to clinical, policy and academic audiences. A key element will be engaging health professionals in patient and carer ideas for promoting self-management of psychological well-being. The study has ethical approval from the North West Research Ethics Committee and the appropriate NHS governance clearance.RegistrationNational Institute for Health Research (NIHR) Clinical Studies Portfolio, UK Clinical Research Network (UKCRN) Study number 11725
Effects of intra- and inter-laminar resin content on the mechanical properties of toughened composite materials
Composite materials having multiphase toughened matrix systems and laminate architectures characterized by resin-rich interlaminar layers (RIL) have been the subject of much recent attention. Such materials are likely to find applications in thick compressively loaded structures such as the keel area of commercial aircraft fuselages. The effects of resin content and its interlaminar and intralaminar distribution on mechanical properties were investigated with test and analysis of two carbon-epoxy systems. The RIL was found to reduce the in situ strengthening effect for matrix cracking in laminates. Mode 2 fracture toughness was found to increase with increasing RIL thickness over the range investigated, and Mode 1 interlaminar toughness was negligibly affected. Compressive failure strains were found to increase with increasing resin content for specimens having no damage, holes, and impact damage. Analytical tools for predicting matrix cracking of off-axis plies and damage tolerance in compression after impact (CAI) were successfully applied to materials with RIL
What is there in the black box of dark energy: variable cosmological parameters or multiple (interacting) components?
The coincidence problems and other dynamical features of dark energy are
studied in cosmological models with variable cosmological parameters and in
models with the composite dark energy. It is found that many of the problems
usually considered to be cosmological coincidences can be explained or
significantly alleviated in the aforementioned models.Comment: 6 pages, 1 figure, talk given at IRGAC2006 (Barcelona, July 11-15,
2006), to appear in J. Phys.
Cosmologies with variable parameters and dynamical cosmon: implications on the cosmic coincidence problem
Dynamical dark energy (DE) has been proposed to explain various aspects of
the cosmological constant (CC) problem(s). For example, it is very difficult to
accept that a strictly constant Lambda-term constitutes the ultimate
explanation for the DE in our Universe. It is also hard to acquiesce in the
idea that we accidentally happen to live in an epoch where the CC contributes
an energy density value right in the ballpark of the rapidly diluting matter
density. It should perhaps be more plausible to conceive that the vacuum
energy, is actually a dynamical quantity as the Universe itself. More
generally, we could even entertain the possibility that the total DE is in fact
a mixture of vacuum energy and other dynamical components (e.g. fields, higher
order terms in the effective action etc) which can be represented collectively
by an effective entity X (dubbed the ``cosmon''). The ``cosmon'', therefore,
acts as a dynamical DE component different from the vacuum energy. While it can
actually behave phantom-like by itself, the overall DE fluid may effectively
appear as standard quintessence, or even mimic at present an almost exact CC
behavior. Thanks to the versatility of such cosmic fluid we can show that a
composite DE system of this sort (``LXCDM'') may have a key to resolving the
mysterious coincidence problem.Comment: LaTeX, 13 pages, 5 figure
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