Drilling holes on CFRP components is inevitable for assembling process in the aviation industry. The drilling-induced damages frequently occur and affect not only the load carrying capacity of ...components but also the reliability. Therefore, it is of great urgency to enhance drilling quality on CFRP components. The article aims to propose a novel drill structure to change the cutting conditions at the drill exit and effectively reduce damages in drilling CFRP. Considering the drilling-exit constraint condition, a unique two-dimensional cutting model is established to represent the axial cutting of the main cutting edge at the drill exit. Based on the model, the effects of point of action and cutting direction on material removal at the exit are investigated, and the result indicates that cutting CFRP in the upward direction has positive effects on deflection limitation and damage reduction. In order to perform the upward cutting, a novel intermittent-sawtooth drill structure is proposed on the one-shot drill. The theoretical and geometrical analyses of the drilling process reveal that the cutting lips of the structure could reverse the cutting direction from downward to upward and thereby, reduce the drill-exit damages. Furthermore, drilling experiments are conducted and the drill structure is proved to be effective to reduce drilling damages as expected.
•A cutting model considering drill-exit constraints is developed for drilling CFRP.•Cutting upward is found based on the model to be positive on the damage reduction.•An intermittent-sawtooth drill structure is proposed to perform the upward cutting.•Burrs and delaminations are effectively suppressed by the novel drill structure.
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•We developed a framework for green-blue-grey measures selection and comparison.•Complex trade-offs among solutions become visible using optimisation techniques.•Hybrid solutions are ...best for multiple benefits in areas with space restrictions.•Considering co-benefits enhancement encourages the selection of green-blue measures.•The primary benefit should not be compromised by pursuing co-benefits.
Climate change is presenting one of the main challenges to our planet. In parallel, all regions of the world are projected to urbanise further. Consequently, sustainable development challenges will be increasingly concentrated in cities. A resulting impact is the increment of expected urban flood risk in many areas around the globe. Adaptation to climate change is an opportunity to improve urban conditions through the implementation of green-blue infrastructures, which provide multiple benefits besides flood mitigation. However, this is not an easy task since urban drainage systems are complex structures. This work focuses on a method to analyse the trade-offs when different benefits are pursued in stormwater infrastructure planning. A hydrodynamic model was coupled with an evolutionary optimisation algorithm to evaluate different green-blue-grey measures combinations. This evaluation includes flood mitigation as well as the enhancement of co-benefits. We confirmed optimisation as a helpful decision-making tool to visualise trade-offs among flood management strategies. Our results show that considering co-benefits enhancement as an objective boosts the selection of green-blue infrastructure. However, flood mitigation effectiveness can be diminished when extra benefits are pursued. Finally, we proved that combining green-blue-grey measures is particularly important in urban spaces when several benefits are considered simultaneously.
•Preliminary assessment of grey infrastructure sites at flood hotspots maximizes its advantages.•Green-grey infrastructures jointly improve their benefits over separate applications.•Optimal design ...of green-grey infrastructures is more cost-effective for higher storms vs lower.•Retrofitting green-grey infrastructure depends on available resources and target design goals.
Green-grey infrastructures implementation for addressing urban flood damages and urban drainage system’ (UDS) resilience (respectively) needs comprehensive evaluation under various planning and design influencing factors. In this paper, a multi-objective decision-making framework is developed for the optimization of green-grey infrastructures to understand the trade-off between benefits and retrofit costs under various design configurations, rainfall intensities, and system performance indicators. In the developed framework, the grey infrastructure locations are optimally determined by using Analytic Hierarchy Process (AHP) method with three defined indicators (e.g., flood volume and flood duration of flooding nodes, sensitivity of flooding nodes) and maximum percentage of each type of green infrastructure (GI) in each sub-catchment based on land-use analysis as a preliminary step of the multi-objective optimization process, followed by decision-making procedure. The application results reveal that optimal designs of grey infrastructure are more cost-effective and may have a significant influence on the reduction of flood damages and outlet peak flow compared to GI from their individual evaluations, while GI improves UDS’ functionality performance indicators (e.g., resilience, reliability, and sustainability) better than grey infrastructure. However, a combined implementation of both infrastructures boosts their advantages because of the synchronization effect compared to individual scenarios, providing the most cost-effective optimal UDS designs. Moreover, the cost-effectiveness of coupled green-grey infrastructures designs could be enhanced from lower to higher design storms because of higher rate of utilization of stormwater infiltration and storage capacities of both infrastructures. The framework presented in this study can be conveniently generalized to other case-studies for optimal implementation of green-grey infrastructures as long as including their local economic parameters, climatic patterns, urban development plans and green-grey infrastructures design guidelines.
Nanocrystalline materials with a high density of grain boundaries have long been reported to alleviate radiation damage. However, a full mechanistic understanding of defect reduction, particularly ...the interaction mechanisms between grain boundaries and clustered defects during irradiation, remains an open question. Here we present atomistic simulations of prolonged radiation damage evolution in Cu bicrystals with increasing radiation dose. Our results reveal the atomic details of defect nucleation and migration, and the mechanisms for the annihilation of defect clusters during irradiation. Stacking fault tetrahedra formed due to radiation damage cascades show preferential migration to irradiated grain boundary. Interstitial-loaded grain boundaries are observed to be dynamically resilient, and persistently interact with the stacking fault tetrahedra, revealing a self-healing response to radiation damage. The results show a synergistic effect of grain boundaries on defect annihilation at small grain spacings of less than 6 nm, giving rise to a drastic decrease in the density of defect clusters. These findings, along with the mechanistic insights, present an integrated perspective on interface-mediated damage reduction in radiation-resistant nanomaterials.
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Understanding and predicting radiation damage is of central importance to develop radiation-tolerant structural materials for current and next-generation nuclear systems. Single-phase solid solution ...alloys constitute attractive choices due to their promising mechanical properties and radiation tolerance. Here, by examining radiation-induced defect production and evolution in single-phase Ni-Fe alloys, we show that radiation damage resistance directly correlates with thermodynamic mixing energy and heterogeneity of defect diffusion. We found that radiation damage in materials decreases linearly with lowering mixing energy, and the relationship holds true for all studied Ni-Fe compositions. The damage reduction with varying composition is further ascribed to the increasing heterogeneity of point defect migration across a complex potential energy landscape that enhances defect recombination. This new insight into the dynamical evolution of radiation defects points to a thermodynamic criterion for designing radiation-tolerant materials.
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Drilling is one of the most common procedures in orthopaedic surgery. However, drilling-induced trauma occurs frequently and affects the processing damage and position accuracy of the holes, which ...strongly influence the postoperative recovery. Therefore, there is an urgent need to design a dedicated drill bit that can satisfy low-trauma requirements such as low cutting force, low temperature, self-centring, and low surface damage during orthopaedic surgery. In this work, a novel three-step drill structure is proposed to modify the cutting conditions at the entrance and exit of drilling, to effectively reduce the mechanical and thermal damages and improve the position accuracy in bone drilling. As the first step drill, a unique tip with thinned web was adopted by considering the drill skidding mechanisms under a non-perpendicular drilling condition. The second step was achieved by using an optimal point angle for balancing the effects of the cutting force and temperature. Moreover, a transition arc design was proposed as the third step to adjust the point angle during the finishing stage for switching the cutting mechanism from ‘fracture & shear crack’ cutting to ‘shear’ cutting in association with a certain range of feeding rates. This could reduce the mechanical and thermal damages to the finished hole surface. Drilling experiments under various process conditions demonstrated that the proposed drill design significantly reduced the drilling force, temperature, and damage and also improved the position accuracy of the holes compared to the conventional drill design. The proposed design provides an effective tool to achieve low-trauma bone drilling in orthopaedic surgery.
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•The presented drill bit can efficiently reduce the drilling force, temperature, damage, and improved the position accuracy.•The drill skidding mainly raised by the unequal cutting areas on the chisel edge and cutting lip of the drill bit.•The transition arc design could successfully improve the hole quality by switching the cutting mechanism.•An advanced experimental set-up was developed for a comprehensive analysis of bone drilling.
Nomex honeycomb component is a typical weak rigid structure, leading to various damages during cutting operation. In this paper, the effects of cutting angles, entrance angle and engagement angle, on ...cutting quality were analyzed by focusing on the cell wall deformation, the cutter-workpiece interaction and the thin-walled cell geometry. A damage reduction method was proposed by controlling the range of the cutting angles. Experiments were conducted to verify the damage reduction method by cutting rectangular Nomex honeycomb core using multi-teeth disc cutters. The results showed that the method has a remarkable effect on the characteristics and distributions of damages by varying cutting angles: (a) the experimental damage-prone range of entrance angle is 55° ~ 75°, and an entrance angle near to 0° or 180° is more beneficial to damage reduction; (b) when engagement angle is smaller than 90°, there will be no visible tear damage; (c) up-cutting direction that makes entrance angle larger than 80° and engagement angle smaller than 90° is effective for damage reduction, leading the damage size is reduced by at least 40%; (d) engagement angle decreases as increasing cutting edge inclination so that the damage size can be further reduced by at least 70%.
Resumo O uso de conceitos e práticas de Redução de Danos (RD) na atenção às pessoas que usam drogas foi iniciado no Brasil nos anos 1990, como resposta preventiva à propagação do HIV/aids. Ao longo ...dos anos, ganhou espaço em outros campos de ação, como a saúde mental e a proteção social. Em 2019, com as mudanças no governo federal, esta prática foi retirada da definição da política sobre drogas. Com foco nos reflexos dessas mudanças, este estudo visou caracterizar quem atua e quais ações são desenvolvidas junto às pessoas que usam drogas, sob a perspectiva da RD, em municípios da região Sul do Brasil (RS, SC e PR). Trata-se de um estudo exploratório descritivo e transversal, que usou um questionário virtual composto por questões abertas, fechadas e métodos mistos de análise de dados. Os participantes foram recrutados por meio do método Snowball Sampling, de forma virtual, alcançando 72 questionários validados. Foi desenvolvida uma análise exploratória dos dados quantitativos. Para as respostas qualitativas foi usada a Análise Textual Discursiva e o software NVivo (versão 12). Os resultados demonstraram o perfil dos profissionais; mudanças ao longo dos anos e a necessidade de ampliar investimentos em pesquisas sobre RD.
Abstract Harm Reduction (HR) concepts and practices in the care of people who use drugs stared being used in Brazil in the 1990s, as a preventive response to the spread of HIV/AIDS. Over the years, it gained space in other fields, such as mental health and social protection. In 2019, with changes in the federal government, this practice was removed from the definitions of the drug policy. Focusing on the consequences of these changes, this study aimed to characterize who works and what actions are developed with the people who use drugs, in the HR perspective, in the southern region of Brazil. This is a descriptive and cross-sectional exploratory study, which used an online questionnaire with open and closed questions, and mixed methods of data analysis. Participants were recruited using the Snowball Sampling method, by virtual means, reaching 72 validated questionnaires. An exploratory analysis of the quantitative data was developed. For the qualitative data, the Discursive Textual Analysis and NVivo software (version 12) were used. The results showed the profile of professionals; the changes over the years; and the need to expand investments in HR research.
Abstract
Floods and droughts and their associated economic, environmental, and social losses or damages are increasing in severity and frequency. Measures taken to reduce these losses or damages ...stemming from extreme events typically depend on how effective they are in reducing the consequences of having either too much or too little water and for longer periods of time. To identify trade-offs between the annual estimated loss or damage reduction, i.e., the benefits, however measured, and the average annual cost of various damage reduction measures, one can perform risk–cost analyses. Because of climate change, the likelihoods of future hydrologic extremes are both changing and uncertain. Also uncertain are any estimates of future damages that would occur given any specific extreme event. In addition, one cannot be certain of the future costs or benefits of damage reduction measures. This paper outlines a range of practical approaches for identifying these trade-offs, taking into account the uncertainties associated with future damages resulting from any specific flood or drought event, the changing uncertainties of future flood and drought events, and the uncertainty of future damage mitigation costs.
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