Research in nonlinear structural and solid mechanics

Recent and projected advances in applied mechanics, numerical analysis, computer hardware and engineering software, and their impact on modeling and solution techniques in nonlinear structural and solid mechanics are discussed. The fields covered are rapidly changing and are strongly impacted by current and projected advances in computer hardware. To foster effective development of the technology perceptions on computing systems and nonlinear analysis software systems are presented

Magnetic resonance imaging of myocardial strain after acute ST-segment-elevation myocardial infarction: a systematic review

The purpose of this systematic review is to provide a clinically relevant, disease-based perspective on myocardial strain imaging in patients with acute myocardial infarction or stable ischemic heart disease. Cardiac magnetic resonance imaging uniquely integrates myocardial function with pathology. Therefore, this review focuses on strain imaging with cardiac magnetic resonance. We have specifically considered the relationships between left ventricular (LV) strain, infarct pathologies, and their associations with prognosis. A comprehensive literature review was conducted in accordance with the PRISMA guidelines. Publications were identified that (1) described the relationship between strain and infarct pathologies, (2) assessed the relationship between strain and subsequent LV outcomes, and (3) assessed the relationship between strain and health outcomes. In patients with acute myocardial infarction, circumferential strain predicts the recovery of LV systolic function in the longer term. The prognostic value of longitudinal strain is less certain. Strain differentiates between infarcted versus noninfarcted myocardium, even in patients with stable ischemic heart disease with preserved LV ejection fraction. Strain recovery is impaired in infarcted segments with intramyocardial hemorrhage or microvascular obstruction. There are practical limitations to measuring strain with cardiac magnetic resonance in the acute setting, and knowledge gaps, including the lack of data showing incremental value in clinical practice. Critically, studies of cardiac magnetic resonance strain imaging in patients with ischemic heart disease have been limited by sample size and design. Strain imaging has potential as a tool to assess for early or subclinical changes in LV function, and strain is now being included as a surrogate measure of outcome in therapeutic trials

Advanced structures technology and aircraft safety

NASA research and development on advanced aeronautical structures technology related to flight safety is reviewed. The effort is categorized as research in the technology base and projects sponsored by the Aircraft Energy Efficiency (ACEE) Project Office. Base technology research includes mechanics of composite structures, crash dynamics, and landing dynamics. The ACEE projects involve development and fabrication of selected composite structural components for existing commercial transport aircraft. Technology emanating from this research is intended to result in airframe structures with improved efficiency and safety

Research in computerized structural analysis and synthesis

Computer applications in dynamic structural analysis and structural design modeling are discussed

Virtual and Face-to-Face Team Collaboration Comparison Through an Agent-Based Simulation

The ongoing COVID-19 pandemic has accelerated the acceptance of virtual team collaboration as a replacement for face-to-face collaboration. Unlike face-to-face collaboration, virtual collaboration is influenced by unique factors, such as technology mediation. However, there is a lack of rigorous research that assesses the impact of virtual collaboration on the engineering design process. Therefore, the current study investigates the effect of virtual team collaboration on design outcomes by means of the model of influence, learning, and norms in organizations (MILANO) framework. To tailor MILANO for virtual collaboration, this paper first presents an empirical study of human design teams, which shows how model parameter values for face-to-face collaboration (like self-efficacy, perceived influencers, perceived degree of influence, trust and familiarity) differ from appropriate parameter values for face-to-face collaboration. The simulation results for both virtual and face-to-face collaboration show how design outcomes differ with collaboration mode. Unlike teams with a few well-defined influential individuals, the mode of collaboration does not have a significant impact on teams where all individuals are equally influential. Virtual collaboration also results in lower exploration and variety than face-to-face collaboration

Idea selection in design teams: a computational framework and insights in the presence of influencers

Idea selection is crucial in design as it impacts the outcome of a project. A collaborative design activity could be considered as a social process where the interactions and individual states (such as the importance in the team and self-efficacy level) could affect decision-making. It is often seen in design teams that some individuals, referred to as 'influencers' in the article have more capacity to influence than others, hence they govern the team process for better or worse. Due to the limited work done in the past to study the effect of these influencers on design outcomes, the work aims at increasing the understanding by presenting some insights from its agent-based simulation. The simulation results show how different influencer team compositions affect design outcomes in terms of quality and exploration of the solutions. The idea selection starts with the agents who are ready with their solution in their 'mind'. The work presented in this article describes a framework for simulating decision-making during idea selection by considering the influencer and majority effect. The empirical study presented in the article verifies the model logic, that is, the presence of influencer and the majority during idea selection and supports the assumption that individuals' agreement on solutions proposed by other team members depends on the degree of influence and past agreement. The results of the simulation show that teams with well-defined influencers produced solutions with higher variety and had more uniform contributions from team members, but also produced solutions of lower quality

Foreshore vegetation in the Peel-Harvey Estuary: changes since the opening of the Dawesville Channel : a report prepared for the Water and Rivers Commission

The Dawesville channel was constructed in April 1994, as part of a management plan to control eutrophication. With increased exchange between the nutrient-rich waters of the estuary and the nutrient-poor waters of the Indian Ocean there was considerable speculation as to the effects of altered water exchange on inundation, salinity, sedimentation and erosion. The work described here examined a number of estuarine characteristics in relation to meteorological factors and geomorphology at ten foreshore sites between April 2001 and March 2002. Comparisons were made between pre and post channel estuary conditions, and vegetation zonation examined

Empresa pública y privatización en un modelo de duopolio: las implicaciones de los costos diferenciales

El análisis reciente que postula la privatización de las empresas públicas tanto en las economías en desarrollo como en las desarrolladas procede del postulado de que la propiedad privada implica una producción más eficiente ceteris paribus. Haciendo a un lado la eficiencia distributiva y fiscal, algunos han promovido la privatización como una reforma que fortalece la eficiencia. Este trabajo analiza el problema de la privatización desde la perspectiva más amplia del bienestar social, puesto que la propiedad pública implica costos unitarios de producción más altos. En particular analizamos un duopolio compuesto por una empresa en la cual el Estado puede tener acciones –lo que resulta en costos unitarios más altos– y otra empresa de propiedad totalmente privada. Hemos elaborado un modelo que ilustra un intercambio entre la ineficiencia productiva asociada con la propiedad pública y la ineficiencia distributiva asociada con la propiedad privada en una industria en donde está presente el poder del mercado. Este modelo concede un contenido económico normativo a la cuestión de la privatización, en donde la propiedad afecta al costo de producción y al comportamiento. De una manera específica, el modelo proporciona una base sobre la cual la participación del Estado en la propiedad es consecuencia del comportamiento de la maximización del bienestar por el Estado, que explícitamente incorpora el intercambio implicado por los factores pertinentes a la propiedad pública y privada. Se ve que el Estado afecta al comportamiento de la empresa, porque elige la participación en la propiedad.

The biology of Australian seagrasses

Seagrasses are angiosperms which have ventured into the marine environment, where they produce totally submerged flowers which are pollinated under water. They occur in many regions of the world,but the following account is concerned primarily with studies on the biology of these plants in Australian waters. It also attempts to contrast some of the features displayed by the seagrasses with those of more familiar terrestrial plants