Optimum design of composite laminates with thermal effects

An analytical approach to determine an optimum laminate for a variety of thermal and mechanical loading combinations is presented. The analysis is performed for a linear elastic material under static mechanical and uniform thermal loadings. The problem is restricted to a unit width and length laminate with angle orientations resulting in an orthotropic, symmetric, and balanced configuration. An objective function defining total strain energy, is formulated and an optimum laminate design determined subject to constraints on stiffness, average coefficient of thermal expansion, and strength. The objective function is formulated in terms of the orientation angles, number of plies, and material properties. The method presented has, in varying degrees, shown that the design of a laminate can be accomplished using strain energy minimization as the primary criteria. The results of various combinations of applied constraints in the optimized design process are presented and discussed

Assessing the climate vulnerability of the world’s natural and cultural heritage

Climate change is the fastest-growing global threat to the world’s natural and cultural heritage. No systematic approach to assess climate vulnerability of protected areas and their associated communities has existed—until now. The Climate Vulnerability Index (CVI) is scientifically robust, transparent, and repeatable, and has now been applied to various World Heritage properties. The CVI builds upon an established Intergovernmental Panel on Climate Change (IPCC) framework to systematically assess vulnerability through a risk assessment approach that considers the key values of the World Heritage property in question and identifies key climate stressors. The CVI process is then used to assess the climate-related vulnerability of the community (including local residents, domestic visitors, and international tourists) associated with the World Heritage property considering economic, social, and cultural connections. Climate impacts are increasingly adding to a wide range of compounding pressures (e.g., increasing tourism, infrastructure development, changing land use practices) that are affecting places, people, customs, and values. Applications of the CVI to date have led to commitments to integrate outcomes into relevant management plans, and to periodically repeat the process, enabling responsive management to changing future circumstances. The CVI has also demonstrated its potential applicability for protected areas beyond World Heritage properties. The CVI process engages local community members in determining impacts, provides opportunities for identifying adaptation and impact mitigation within the community, and aids broader communication about key climate issues

The 30/20 GHz communications system functional requirements

The characteristics of 30/20 GHz usage in satellite systems to be used in support of projected communication requirements of the 1990's are defined. A requirements analysis which develops projected market demand for satellite services by general and specialized carriers and an analysis of the impact of propagation and system constraints on 30/20 GHz operation are included. A set of technical performance characteristics for the 30/20 GHz systems which can serve the resulting market demand and the experimental program necessary to verify technical and operational aspects of the proposed systems is also discussed

Promissory Note, 14 August 1844

https://egrove.olemiss.edu/aldrichcorr_b/1092/thumbnail.jp

Development of an orthotropic hole element

A finite element was developed which adequately represents the state of stress in the region around a circular hole in orthotropic material experiencing reasonably general loading. This was achieved with a complementary virtual work formulation of the stiffness and stress matrices for a square element with center circular hole. The assumed stress state provides zero shearing stress on the hole boundary, so the element is suitable for problems involving load transfer without friction. The element has been implemented in the NASTRAN computer program, and sample problem results are presented

Incorporating spatial correlations into multispecies mean-field models

In biology, we frequently observe different species existing within the same environment. For example, there are many cell types in a tumour, or different animal species may occupy a given habitat. In modeling interactions between such species, we often make use of the mean-field approximation, whereby spatial correlations between the locations of individuals are neglected. Whilst this approximation holds in certain situations, this is not always the case, and care must be taken to ensure the mean-field approximation is only used in appropriate settings. In circumstances where the mean-field approximation is unsuitable, we need to include information on the spatial distributions of individuals, which is not a simple task. In this paper, we provide a method that overcomes many of the failures of the mean-field approximation for an on-lattice volume-excluding birth-death-movement process with multiple species. We explicitly take into account spatial information on the distribution of individuals by including partial differential equation descriptions of lattice site occupancy correlations. We demonstrate how to derive these equations for the multispecies case and show results specific to a two-species problem. We compare averaged discrete results to both the mean-field approximation and our improved method, which incorporates spatial correlations. We note that the mean-field approximation fails dramatically in some cases, predicting very different behavior from that seen upon averaging multiple realizations of the discrete system. In contrast, our improved method provides excellent agreement with the averaged discrete behavior in all cases, thus providing a more reliable modeling framework. Furthermore, our method is tractable as the resulting partial differential equations can be solved efficiently using standard numerical techniques

Documentation of Infanticide and Cannibalism in Bald Eagles

Non-kin infanticide, the killing of dependent young by unrelated conspecifics, occurs in a wide array of taxonomic groups including mammals, insects, fish, and birds (Hrdy 1979, Hrdy and Hausfater 1984). Several hypotheses have been proposed to explain this behavior including the removal of potential competitors to gain access to limited resources such as nesting territories and food (Hrdy 1979)..

Rainy downdrafts in abyssal atmospheres

Results from Juno's microwave radiometer indicate non-uniform mixing of ammonia vapor in Jupiter's atmosphere down to tens of bars, far beneath the cloud level. Helioseismic observations suggest solar convection may require narrow, concentrated downdrafts called entropy rain to accommodate the Sun's luminosity. Both observations suggest some mechanism of non-local convective transport. We seek to predict the depth that a concentrated density anomaly can reach before efficiently mixing with its environment in bottomless atmospheres. We modify classic self-similar analytical models of entraining thermals to account for the compressibility of an abyssal atmosphere. We compare these models to the output of high resolution three dimensional fluid dynamical simulations to more accurately model the chaotic influence of turbulence. We find that localized density anomalies propagate down to ~3-8 times their initial size without substantially mixing with their environment. Our analytic model accurately predicts the initial flow, but the self-similarity assumption breaks down after the flow becomes unstable at a characteristic penetration depth. In the context of Jupiter, our findings suggest that precipitation concentrated into localized downdrafts of size ~20km can coherently penetrate to on the order of a hundred kilometers (tens of bars) beneath its initial vaporization level without mixing with its environment. This finding is consistent with expected convective storm length-scales, and Juno MWR measurements of ammonia depletion. Compositional gradients of volatiles beneath their cloud levels may be common on stormy giant planets. In the context of the Sun, we find that turbulent downdrafts in abyssal atmospheres cannot maintain their coherence through the Sun's convective layer, a potential challenge for the entropy rain hypothesis.Comment: 20 pages, 16 figures. Accepted by A&