Purpose: The present study deals with the numerical modeling of the low-velocity impact damage of laminated composites which have increasingly important applications in aerospace primary structures. Such damage, generated by various sources during ground handling, substantially reduces the mechanical residual performance and the safe-service life. The purpose of this paper is to present and validate a computationally efficient approach in order to explore the effect of critical parameters on the impact damage characteristics.Design/methodology/approach: Numerical modeling is considered as one of the most efficient tool as compared to the expensive and time-consuming experimental testing. In this paper, a finite element model based on explicit dynamics formulations is adopted. Hashin criterion is applied to predict the intralaminar damage initiation and evolution. The numerical analysis is performed using the ABAQUS® programme. Findings: The employed modeling approach is validated using corresponding numerical data found in the literature and the presented results show a reasonable correlation to the available literature data. It is demonstrated that the current model can be used to capture the force-time response as well as damage parameter maps showing the intralaminar damage evolution for different impact cases with respect to the physical boundary conditions and a range of impact energies. Originality/value: Low-velocity impact damage of laminated composites is still not well understood due to the complexity and non-linearity of the damage zone. The presented model is used to predict the force-time response which is considered as one of the most important parameters influencing the structural integrity. Furthermore, it is used for capturing the damage shape evolution, exhibiting a high degree of capability as a damage assessment computational tool.
DOCUMENT
Laminated composites have important applications in modern aeronautical structures due to their extraordinary mechanical and environmental behaviour. Nevertheless, aircraft composite structures are highly vulnerable to impact damage, either by low-velocity sources during maintenance or high-velocity sources during in-flight events. Even barely visible impact damage induced by low-velocity loading, substantially reduces the residual mechanical performance and the safe-service life of the composites structures. Despite the extensive research already carried out, impact damage of laminated composite structures is still not well understood and it is an area of on-going research. Numerical modelling is considered as the most efficient tool as compared to the expensive and time-consuming experimental testing. In this paper, a finite element model based on explicit dynamics formulations is adopted. Hashin criterion is applied to predict the intra-laminar damage initiation and evolution. The numerical analysis is performed using the ABAQUS ® programme. The employed modelling approach is validated using numerical results found in the literature and the presented results show an acceptable correlation to the available literature data. It is demonstrated that the presented model is able to capture force-time response as well as damage evolution map for a range of impact energies.
DOCUMENT
DBELA is a Displacement-Based Earthquake Loss Assessment methodology for urban areas which relates the displacement capacity of the building stock to the displacement demand from earthquake scenarios. The building stock is modeled as a random population of building classes with varying geometrical and material properties. The period of vibration of each building in the random population is calculated using a simplified equation based on the height of the building and building type, whilst the displacement capacity at different limit states is predicted using simple equations which are a function of the randomly simulated geometrical and material properties. The displacement capacity of each building is then compared to the displacement demand obtained, from an over-damped displacement spectrum, using its period of vibration; the proportion of buildings which exceed each damage state can thus be estimated. DBELA has been calibrated to the Turkish building stock following the collection of a large database of structural characteristics of buildings from the northern Marmara region. The probabilistic distributions for each of the structural characteristics (e.g. story height, steel properties etc.) have been defined using the aforementioned database. The methodology has then been applied to predict preliminary damage distributions and social losses for the Istanbul Metropolitan Municipality for a Mw 7.5 scenario earthquake.
MULTIFILE
From the article: Abstract Sub-chronic toxicity studies of 163 non-genotoxic chemicals were evaluated in order to predict the tumour outcome of 24-month rat carcinogenicity studies obtained from the EFSA and ToxRef databases. Hundred eleven of the 148 chemicals that did not induce putative preneoplastic lesions in the sub-chronic study also did not induce tumours in the carcinogenicity study (True Negatives). Cellular hypertrophy appeared to be an unreliable predictor of carcinogenicity. The negative predictivity, the measure of the compounds evaluated that did not show any putative preneoplastic lesion in de sub-chronic studies and were negative in the carcinogenicity studies, was 75%, whereas the sensitivity, a measure of the sub-chronic study to predict a positive carcinogenicity outcome was only 5%. The specificity, the accuracy of the sub-chronic study to correctly identify non-carcinogens was 90%. When the chemicals which induced tumours generally considered not relevant for humans (33 out of 37 False Negatives) are classified as True Negatives, the negative predictivity amounts to 97%. Overall, the results of this retrospective study support the concept that chemicals showing no histopathological risk factors for neoplasia in a sub-chronic study in rats may be considered non-carcinogenic and do not require further testing in a carcinogenicity study.
DOCUMENT
A damage estimation exercise has been carried out using the building stock inventory and population database of the Istanbul Metropolitan Municipality and selected European earthquake loss estimation packages: KOERILOSS, SELENA, ESCENARIS, SIGE, and DBELA. The input ground-motions, common to all models, correspond to a “credible worst case scenario” involving the rupture of the four segments of the Main Marmara Fault closest to Istanbul in a Mw 7.5 earthquake. The aim of the exercise is to assess the applicability of the selected software packages to earthquake loss estimation in the context of rapid post-earthquake response in European urban centers. The results in terms of predicted building damage and social losses are critically compared amongst each other, as well as with the results of previous scenario-based earthquake loss assessments carried out for the study area. The key methodological aspects and data needs for European rapid post-earthquake loss estimation are thus identified.
LINK
Background: Falls in stroke survivors can lead to serious injuries and medical costs. Fall risk in older adults can be predicted based on gait characteristics measured in daily life. Given the different gait patterns that stroke survivors exhibit it is unclear whether a similar fall-prediction model could be used in this group. Therefore the main purpose of this study was to examine whether fall-prediction models that have been used in older adults can also be used in a population of stroke survivors, or if modifications are needed, either in the cut-off values of such models, or in the gait characteristics of interest. Methods: This study investigated gait characteristics by assessing accelerations of the lower back measured during seven consecutive days in 31 non fall-prone stroke survivors, 25 fall-prone stroke survivors, 20 neurologically intact fall-prone older adults and 30 non fall-prone older adults. We created a binary logistic regression model to assess the ability of predicting falls for each gait characteristic. We included health status and the interaction between health status (stroke survivors versus older adults) and gait characteristic in the model. Results: We found four significant interactions between gait characteristics and health status. Furthermore we found another four gait characteristics that had similar predictive capacity in both stroke survivors and older adults. Conclusion: The interactions between gait characteristics and health status indicate that gait characteristics are differently associated with fall history between stroke survivors and older adults. Thus specific models are needed to predict fall risk in stroke survivors.
DOCUMENT
Abstract: The key challenge of managing Floating Production Storage and Offloading assets (FPSOs) for offshore hydrocarbon production lies in maximizing the economic value and productivity, while minimizing the Total Cost of Ownership and operational risk. This is a comprehensive task, considering the increasing demands of performance contracting, (down)time reduction, safety and sustainability while coping with high levels of phenomenological complexity and relatively low product maturity due to the limited amount of units deployed in varying operating conditions. Presently, design, construction and operational practices are largely influenced by high-cycle fatigue as a primary degradation parameter. Empirical (inspection) practices are deployed as the key instrument to identify and mitigate system anomalies and unanticipated defects, inherently a reactive measure. This paper describes a paradigm-shift from predominant singular methods into a more holistic and pro-active system approach to safeguard structural longevity. This is done through a short review of several synergetic Joint Industry Projects (JIP’s) from different angles of incidence on enhanced design and operations through coherent a-priori fatigue prediction and posteriori anomaly detection and -monitoring.
DOCUMENT
This paper outlines an investigation into the updating of fatigue reliability through inspection data by means of structural correlation. The proposed methodology is based on the random nature of fatigue fracture growth and the probability of damage detection and introduces a direct link between predicted crack size and inspection results. A distinct focus is applied on opportunities for utilizing inspection information for the updating of both inspected and uninspected (or uninspectable) locations.
DOCUMENT
Anthropology is traditionally broken into several subfields, physical/biological anthropology, social/cultural anthropology, linguistic anthropology, archaeology, and sometimes also applied anthropology. Anthropology of the environment, or environmental anthropology, is a specialization within the field of anthropology that studies current and historic human-environment interactions. Although the terms environmental anthropology and ecological anthropology are often used interchangeably, environmental anthropology is considered by some to be the applied dimension of ecological anthropology, which encompasses the broad topics of primate ecology, paleoecology, cultural ecology, ethnoecology, historical ecology, political ecology, spiritual ecology, and human behavioral and evolutionary ecology. However, according to Townsend (2009: 104), “ecological anthropology will refer to one particular type of research in environmental anthropology—field studies that describe a single ecosystem including a human population and frequently deal with a small population of only a few hundred people such as a village or neighborhood.” Kottak states that the new ecological anthropology mirrors more general changes in the discipline: the shift from research focusing on a single community or unique culture “to recognizing pervasive linkages and concomitant flows of people, technology, images, and information, and to acknowledging the impact of differential power and status in the postmodern world on local entities. In the new ecological anthropology, everything is on a larger scale” (Kottak 1999:25). Environmental anthropology, like all other anthropological subdisciplines, addresses both the similarities and differences between human cultures; but unlike other subdisciplines (or more in line with applied anthropology), it has an end goal—it seeks to find solutions to environmental damage. While in our first volume (Shoreman-Ouimet and Kopnina 2011) we criticized Kottak’s anthropocentric bias prioritizing environmental anthropology's role as a supporter of primarily people's (and particularly indigenous) interests rather than ecological evidence. In his newer 2 publication, Kottak (2010:579) states: “Today’s ecological anthropology, aka environmental anthropology, attempts not only to understand but also to find solutions to environmental problems.” And because this is a global cause with all cultures, peoples, creeds, and nationalities at stake, the contributors to this volume demonstrate that the future of environmental anthropology may be more focused on finding the universals that underlie human differences and understanding how these universals can best be put to use to end environmental damage. This is an Accepted Manuscript of a book chapter published by Routledge/CRC Press in "Environmental Anthropology: Future Directions" on 7/18/13 available online: https://doi.org/10.4324/9780203403341 LinkedIn: https://www.linkedin.com/in/helenkopnina/
MULTIFILE
Prophylactic replacement therapy is the cornerstone of treatment in severe haemophilia. Regular infusions with clotting factor concentrate have been proven effective to prevent bleeding, subsequent (joint) damage, and positively affect the impact of haemophilia on daily life [1]. Patients or parents of younger patients learn to infuse clotting factor concentrate in a peripheral vein (i.v.) or a central venous access device (CVAD) [2].
DOCUMENT
