Zoekresultaten

A model of low-velocity impact damage assessment of laminated composite structures

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.

Health and Social Needs of Traumatized Refugees and Asylum Seekers: An Exploratory Study

The purpose of this study was to describe the care needs of adult traumatized refugees and asylum seekers. DESIGN AND METHODS.  A mixed-methods design was used. A survey was conducted using the Camberwell Assessment of Need (CAN) among 30 patients. Semistructured in-depth interviews were subsequently conducted with eight of these patients. FINDINGS.  Key themes among refugees are loneliness and grief. Refugees are in severe psychological distress. They also encounter all kinds of practical problems that influence their quality of life. Furthermore, many of them suffer from serious psychiatric and trauma-related problems. PRACTICE IMPLICATIONS.  The results of this explorative study can contribute to the quality of care for traumatized refugees.

Mechanisms for sustainable use of biodiversity in and beyond natural ecosystems

The increasing demand for Prunus africana resources is an opportunity for its conservation and commercial use to support livelihoods in Africa. The objective for this study was to investigate major steps to advance production of P. africana for long-term commercial use in Uganda. Specific objectives were to explore potential production schemes, setbacks in production and strategies to advance it. The study was done by review of literature, documents and interviews with experts. Results indicated Agroforestry and large plantations to be useful schemes for production. Identified setbacks are: low trade in P. africana, unknown returns from production, competing land uses, long growth period, limited market assurance and information. The lack of a resource assessment for P. africana in forests contributes to its low trade which undermines related economic benefits for national development and incentives to commercial production. We propose that a national Quantitative resource assessment of P. africana in forests is one of the crucial steps that should be undertaken to carefully organise and advance sustainable trade to provide rational incentives for commercial production. Subsequently, production should be localised in suitable sites and producers be organised into cooperatives. Further research to improve returns from commercial production of P. africana is needed.

Investigations on the restoration and seismic enhancement options for the jaisedewal temple after the Gorkha eartquake in Nepal

Early detection of extremism? The local security professional on assessment of potential threats posed by youth

Frontline professionals such as social workers and civil servants play a crucial role in countering violent extremism.Because of their direct contac twith society,first liners are tasked with detecting individuals that may threaten national security and the democratic rule of law. Preliminary screening takes place during the pre-crime phase. However, without clear evidence or concrete indicators of unlawful action or physical violence, it is challenging to determine when someone poses a threat. There are no set patterns that can be used to identify cognitive radicalization processes that will result in violent extremism. Furthermore, prevention targets ideas and ideologies with no clear framework for assessing terrorism-risk. This article examines how civil servants responsible for public order, security and safety deal with their mandate to engage in early detection, and discusses the side effects that accompany this practice. Based on openinterviews with fifteen local security professionals in the Netherlands, we focus here on the risk assessments made by these professionals. To understand their performance, we used the following two research questions: First, what criteria do local security professionals use to determine whether or not someone forms a potential risk? Second, how do local security professionals substantiate their assessments of the radicalization processes that will develop into violent extremism? We conclude that such initial risk weightings rely strongly on ‘gut feelings’ or intuition. We conclude that this subjectivitymayleadto prejudiceand/oradministrativearbitrariness in relationtopreliminary risk assessment of particular youth.

Mechanical modelling of cavity wall metal ties

The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is of high relevance in regions such as in Central and Northern Europe, Australia, New Zealand and China because of the characteristics of the masonry building stock. A cavity wall consists of two separate parallel walls usually connected by metal ties. Cavity walls are particularly vulnerable to earthquakes, as the out-of-plane capacity of each individual leaf is significantly smaller than the one of an equivalent solid wall. This paper presents the results of an experimental campaign conducted by the authors on metal wall tie connections and proposes a mechanical model to predict the cyclic behaviour of these connections. The model has been calibrated by us- ing the experimental results in terms of observed failure modes and force-displacement responses. Results are also presented in statistical format.