95,016 research outputs found
Experimental response of a low-yielding, self-centering, rocking column base joint with friction dampers
No full textThe sliding hinge joint (SHJ) is a supplemental energy dissipation system for column bases or beam-to-column connections of steel Moment Resisting Frames (MRFs). It is based on the application of symmetric/asymmetric friction dampers to develop a dissipative mechanism alternative to the column/beam yielding. This typology was initially proposed in New Zealand and, more recently, is starting to be tested and applied also in Europe. While on the one hand this technology provides great benefits such as the damage avoidance, on the other hand, due to the high unloading stiffness of the dampers in tension or compression, its cyclic response is typically characterized by a limited self-centering capacity. To address this shortcoming, the objective of the work herein presented is to examine the possibility to add to these connections also a self-centering capacity proposing new layouts based on a combination of friction devices (providing energy dissipation capacity), pre-loaded threaded bars and disk springs (introducing in the joint restoring forces). In this paper, as a part of an ongoing wider experimental activity regarding the behavior of self-centering connections, the attention is focused on the problem of achieving the self-centering of the column bases of MRFs by studying a detail consisting in a column-splice equipped with friction dampers and threaded bars with Belleville disk springs, located above a traditional full-strength column base joint. The main benefits obtained with the proposed layout are that: (i) the self-centering capability is obtained with elements (threaded bars and Belleville springs) which have a size comparable to the overall size of the column-splice cover plates; (ii) all the re-centering elements are moved far from the concrete foundation avoiding any interaction with the footing. The work reports the main results of an experimental investigation and the analysis of a MRF equipped with the proposed column base joints
Seismic assessment of nineteenth and twentieth centuries URM buildings in Lisbon: structural features and derivation of fragility curves
No full textThe article addresses the seismic vulnerability assessment of a typology of unreinforced masonry buildings constructed in Lisbon between the nineteenth and the twentieth centuries. The main architectural and structural features of these buildings are presented. This supported the identification of the main uncertainties affecting their seismic performance and the definition of classes of buildings representative of the typology. The seismic assessment includes the generation of fragility curves that combine the in-plane and out-of-plane response following different criteria and methods of analyses. The results put in evidence the seismic vulnerability of this class of buildings. Considering the earthquake-resistant code for Lisbon with a return period of 475 years, about 50% probability of having heavy damage and about 30% probability of collapse were estimated. The structural intervention on these buildings is urgent in order to reduce losses due to future earthquakes. Further studies for the assessment of similar buildings in Lisbon and elsewhere can be developed using the adopted procedure.The first author would like to acknowledge the financial support of Fundacao para a Ciencia e a Tecnologia (FCT, Ministerio da Educacao e Ciencia, Portugal) through the scholarship PD/BD/106076/2015 through the FCT Doctoral Program: Analysis and Mitigation of Risks in Infrastructures, INFRARISK-(http://infrarisk.tecnico.ulisboa.pt).The authors would also like to acknowledge the contribution from Bruno Silva (Instituto Superior Tecnico) and Nuno Mendes (University of Minho) regarding the ambient vibration tests
Fragility functions for tall URM buildings around early 20th century in Lisbon. Part 2: Application to different classes of buildings
No full textThis article describes the application of the procedure for the derivation of fragility functions presented in the companion article entitled Fragility functions for tall URM buildings around early 20th century in Lisbon. Part 1: methodology and application at building level. The procedure, based on the execution of non-linear analyses, was developed to be applied to unreinforced masonry buildings considering both the in-plane and out-of-plane response. Different sources of uncertainty, both epistemic and aleatory, affecting the behaviour of these unreinforced masonry buildings are discussed and treated with a probabilistic procedure. The fragility curves determined for the different classes of buildings are compared and then combined to define the final fragility curves for these unreinforced masonry buildings. The results put in evidence the high seismic vulnerability of these buildings and the urgent need for the structural intervention and for the design of retrofitting measures in order to reduce potential losses due to future earthquakes.The first author would like to acknowledge the financial support of Fundacao para a Ciencia e a Tecnologia (FCT, Ministerio da Educacao e Ciencia, Portugal) through the scholarship PD/BD/106076/2015 through the FCT Doctoral Program: Analysis and Mitigation of Risks in Infrastructures, INFRARISK (http://infrarisk.tecnico.ulisboa.pt)
LIFE SATISFACTION AND FUTURE EXPECTATIONS AMONG YOUNG NEETS: A MIXED METHOD APPROACH
No full textThis study examines life satisfaction and future expectations among young NEETs (Not in Education, Employment, or Training) in Italy using a mixed-method approach. Based on a sample of 930 individuals aged 25-29, the research explores both the hedonic and eudaimonic dimensions of well-being. Study 1 employs a binary logit model to analyze the impact of socio-demographic factors, self-efficacy, and trauma-related symptoms (TSC) on life satisfaction. Findings indicate higher life satisfaction among women, caregivers, individuals with higher education, and those from southern regions
Development and yields of the tachinid Exorista larvarum in three common Noctuidae of Azores Archipelago and in a laboratory host
No full textThe development of the tachinid larval parasitoid Exorista larvarum (L.) was studied upon Peridroma saucia (Hübner), Pseudaletia unipuncta (Haworth) and Xestia c-nigrum (L.) (Lepidoptera Noctuidae), all of them being common pests of pastures and horticultural crops in the Azores Archipelago, and in the laboratory host Galleria mellonella L. The study occurred under laboratory conditions, but relied on noctuids samples collected on Terceira island. The experiments were conducted at 15, 20 and 25 °C to determine the effect of temperatures commonly recorded in the Azores throughout the year on the tachinid development. All host species were accepted by E. larvarum females, but more eggs were laid on the noctuids than on G. mellonella both at 20 and 25 °C. The effect of temperature on the number of eggs laid was significant only for G. mellonella and X. c-nigrum, although on all species fewer eggs were laid at 15 °C (the mean winter temperature in the Azores). At 15 °C, no puparia were obtained from any host species. At 20 °C no puparia formed in G. mellonella and parasitoid pupation percentages were extremely low also in the noctuids. At 25 °C the puparial yields obtained in the latter were considerably lower than those found in G. mellonella (=13%).
In all moth species, including noctuids, host larval mortality was however very high despite the low percentages of puparia obtained. The efficiency of E. larvarum as a biocontrol agent could be enhanced by host mortality due to incomplete parasitoid development
The Anopheles FBN9 immune factor mediates Plasmodium species-specific defense through transgenic fat body expression
No full textThe Importance of Renewable Energy Systems in Meeting Rising Energy Needs of Megacities in a Sustainable Way: Case Study of Greater Cairo
No full textMegacities are mainly located in developing countries and face challenges in building infrastructures to ensure modern and clean energy access to citizens while coping with lifestyle changes. This paper assesses the renewables impact on energy transition for megacities (supply and all demand sectors) using the Greater Cairo megacity as case study. The MARKAL-EFOM System (TIMES) model is applied to the Greater Cairo region to investigate how energy supply and demand will evolve till 2050, and what are the impacts in terms of final energy consumption, GHG emissions, as well as share of renewable energy sources consumption in total final energy consumption considering two different emissions mitigation caps, namely 50% and 80%. Compared to the business as usual scenario, the final energy consumption decreases of 46 PJ and 57 PJ respectively in the scenarios with the CO2 cap of 50% and 80%. Besides, the TIMES-Greater Cairo shows that the fossil free energy options are limited and thus, in order to meet the emission cap, it is necessary to deploy more energy efficient technologies than in the scenarios without the cap. Transport is the sector with the higher CO2 emissions contribution and the optimization results show that it may lower the environmental impact of 28% by 2050 with the sole deployment of more efficient technologies
Updating on in-vivo and in-vitro effects of heparin and other glycosaminoglycans (mesoglycan) on arterial endothelium: a morphometric study
No full textGlycosaminoglycans, which include heparin, heparansulfate and dermatansulfate, are substances that exhibit many significant biological activities. In-vitro and in-vivo experiments for studying the effects of heparin and an association of heparan-like glycosaminoglycan and dermatansolfate (mesoglycan) on aortic arterial endothelium were performed. The studies were developed by means of computerized morphometric techniques. The in-vitro tests, performed on bovine aortic endothelial cells, have revealed an increase in survival rate, enhancement of cell density at confluence, and increase of nucleus/cytoplasm ratio, after "in-vitro" administration of heparin or mesoglycan. The in-vivo tests have revealed a minor development of aortic intimal lipid deposition in mesoglycan-treated hypercholesterolaemic rabbits. Our morphometrical results confirmed by statistical tests strongly support the data collected in the literature over many years on the protective effects of mesoglycan and heparin on endothelium
Response of friction joints under different velocity rates
No full textThe studies related to the behaviour of steel connections subjected to extreme conditions originated from impact loads have increased in the last few years. However, there is still no consensus on how exactly the whole connection and its individual components behave when subjected to high strain rates, which is translated by the lack of codified design rules. In order to provide a contribution to increase the knowledge on the behaviour of connections under impact loads, in this paper, the response of an innovative friction connection subjected to both quasi-static and rapidly applied loads is examined. This investigation is performed by means of experimental testing, a numerical investigation and analytical developments. A satisfactory agreement between the numerical simulations and the experimental tests was obtained in terms of global and local behaviour of the connection and of its individual components. Afterwards, using the calibrated numerical model, the effect of several parameters were studied: the bending direction, the ductility of the members and the velocity of the application of the load. Finally, an analytical spring model based on the component method currently codified in Eurocode 3 part 1.8 was also developed. This model showed to be able to predict the connection behaviour when subjected to different velocities by just incorporating the strain rate influence on the individual components of the connection
Preliminary investigation of a novel controlled stiffness proximal femoral prosthesis
No full textPrevious studies have suggested that a controlled stiffness prosthesis is required to address the conflicting requirements of minimizing stress shielding and micromotion. The design for a controlled stiffness prosthesis is proposed and a preliminary analytical investigation performed to assess its predicted performance before fabrication of a prototype component. The novel prosthesis consisted of a cobalt–chrome core and a flexible composite outer layer. Varying the composite layer thickness allowed the prosthesis stiffness to be controlled. Three variants of the controlled stiffness prosthesis were critically assessed using the finite element method and their predicted performance compared with those of conventional prosthesis designs. The potential for stress shielding was assessed by examining the periosteal strain energy and the potential for migration assessed by examining the endosteal minimum principal cancellous bone stresses. Both the conventional and controlled stiffness implants performed poorly as press-fit prostheses. All the press-fit prostheses generated high cancellous bone stresses, suggesting that excessive migration of these implants would be likely. The controlled stiffness implants performed better than the conventional implants when bonded to the surrounding bone. Although the controlled stiffness implants did not eliminate stress shielding of the calcar, they produced higher strain energies than the conventional designs. The findings of this study are that osseointegrated controlled stiffness implants may perform better than current osseointegrated cementless prostheses and therefore it is worth while progressing to the next stage, of prototyping an implant
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