Catalogue Search | MBRL
هل أنت متأكد أنك تريد إزالة الكتاب من الرف؟
{{itemTitle}}
1,184
نتائج ل
"Jean, Carlo"
صنف حسب:
Vibration signal analysis using symbolic dynamics for gearbox fault diagnosis
This paper addresses the use of two algorithms based on symbolic dynamics analysis of vibration signal for fault diagnosis in gearboxes. The symbolic dynamics algorithm (SDA) works by subdividing the phase space described by the Poincaré plot into several angular regions; then, a symbol is assigned to each region. The probability distributions generated by the set of symbols are considered as features for classification of faults in a gearbox. The peak symbolic dynamics algorithm (PSDA) is a variant that extracts a sequence of peaks from the vibration signals and then performs the phase-space subdivision and symbol coding. A gearbox vibration signal dataset is analyzed for classifying 10 types of faults. Fault classification is attained using a multi-class support vector machine. The highest accuracy attained using
k
-fold cross-validation is 100.0% for load L3 with SDA and 100% with load L2 with PSDA. The accuracy considering all signals in the gearbox dataset is 99.2% with SDA and 99.8% with PSDA. The algorithms proposed have the advantage of being simple, accurate, and fast, and they could be adapted for online condition monitoring.
Journal Article
Environmental filters predict the trait composition of fish communities in reservoir cascades
Dam construction alters flow regimes and can change the composition of aquatic communities. Using data from three Brazilian hydrographic basins, we tested the hypothesis that reservoir cascades act as environmental filters for fish traits. This dataset included information on different environmental variables and fish traits (diet, migration, fecundation, parental care, position in the water column, and body size), and we used multivariate analysis (partial RLQ) to quantify the relationships between environmental variables, species abundance and traits. We found that the abundance of migratory species declined towards downstream reservoirs, which tend to be smaller and less turbid with a shorter water residence time than upstream reservoirs. We also found evidence of an association between reservoir age and the domination of fish communities by small-sized species with parental care, external fecundation, and benthic habits. Our findings suggest that particular fish traits are selected for across reservoir cascades.
Journal Article
Ecosystem-Based Adaptation Projects, More than just Adaptation: Analysis of Social Benefits and Costs in Colombia
Ecosystem-based Adaptation (EbA) projects are increasingly flourishing throughout the globe on the grounds that EbA constitutes a particularly community-friendly solution for adaptation to climate change as it brings about an array of co-benefits. However, the promotion of EbA projects, by development agencies and conservation NGOs, remains blurry as it has not yet been contrasted against evidence on its effectiveness in delivering these benefits. Employing a political ecology perspective, the applied conceptual framework allows for the assessment of the social benefits and costs that EbA projects generate or reinforce and factors that influence the distribution of these social benefits or costs. This research is done in regards to two EbA projects in Colombia: one in the Andes focusing on water provision services from páramos, and the other in a coastal mangrove focusing on regulation services of extreme coastal events. Based on data collected by a qualitative multi-method approach, we find evidence that the assessed EbA projects generate a wide range of perceived social benefits and costs for the local communities living in the vicinity of the project sites. Furthermore, we identify agent-level (i.e., capitals and preferences) as well as structural factors (communication, participation, local and institutional context) that influence the generation and distribution of those social benefits and costs. Finally, this paper illustrates some of the contradictions and tensions in which EbA projects are implemented and how they may end up affecting the adaptive capacity of the communities involved in EbA projects.
Journal Article
Systematic review of experiences and perceptions of key actors and organisations at multiple levels within health systems internationally in responding to COVID-19
COVID-19 has presented challenges to healthcare systems and healthcare professionals internationally. After one year of the pandemic, the initial evidence on health system responses begins to consolidate, and there is a need to identify and synthesise experiences of responding to COVID-19 among healthcare professionals and other health system stakeholders. This systematic review of primary qualitative studies depicts the experiences and perceptions of organisations and actors at multiple levels of health systems internationally in responding to COVID-19.
Six main databases of biomedical information, public health and health administration research were searched over the period October 1, 2019, to October 21, 2020. Information extracted from included studies was analysed thematically.
Thirty-four studies were eligible for data extraction. Nine of those studies, of lower methodological quality, were removed from the thematic analysis of study results. Considering the professional level experiences, predominant themes of the studies consisted of the new roles and responsibilities of healthcare workers, burnout and distress, recognition of ´unseen´ healthcare workers, and positive changes and emergent solutions amid the crisis. Organisational level findings of the studies included provision of psychological support, COVID-19 as \"catalyst\" for change, and exercise of more \"open\" leadership by managers and health authorities. Continuous training, regulation of working conditions, providing supportive resources, coordinating a diversity of actors, and reviewing and updating regulations were roles identified at the local health system level.
The experiences of frontline healthcare workers have been the focus of attention of the majority of primary qualitative studies as of October 2020. However, organisational and wider system level studies indicate that some responses to COVID-19 have been characterised by increased emphasis on coordination activities by local health system actors, making service adaptations at pace, and reliance on expanded roles of front-line workers. The need for theory-informed qualitative studies was identified at the organisational level.
CRD42020202875.
Journal Article
Health–Aware and Fault–Tolerant Control of an Octorotor UAV System Based on Actuator Reliability
A major goal in modern flight control systems is the need for improving reliability. This work presents a health-aware and fault-tolerant control approach for an octorotor UAV that allows distributing the control effort among the available actuators based on their health information. However, it is worth mentioning that, in the case of actuator fault occurrence, a reliability improvement can come into conflict with UAV controllability. Therefore, system reliability sensitivity is redefined and modified to prevent uncontrollable situations during the UAV’s mission. The priority given to each actuator is related to its importance in system reliability. Moreover, the proposed approach can reconfigure the controller to compensate actuator faults and improve the overall system reliability or delay maintenance tasks.
Journal Article
Environmental degradation of streams leads to the loss of ecomorphologically similar fish species
Human activities change the environmental conditions of streams and alter their assemblages. However, the environmental factors associated with the change in the ecomorphological similarity of the fish assemblage have not been investigated enough. In this context, we sampled data from three urban and six rural streams in the Pirapó River Basin to assess which environmental factors influence the taxonomic and ecomorphological structures of the fish assemblage. We hypothesized that (1) streams with greater environmental heterogeneity have higher species diversity; (2) the greater species diversity is associated with a greater diversity of body shapes and coexistence of more ecomorphologically distinct species. Twenty-two ecomorphological indices related to the food acquisition, locomotion, and habitat use of species were used to calculate interspecific ecomorphological distances that were analyzed using principal component analysis and multiple linear regression. The results show that the rural streams showed less degraded environmental conditions and greater environmental heterogeneity than the urban ones, which was related to the increase in species diversity and ecomorphological similarity of the assemblage. We can conclude that streams containing greater environmental heterogeneity can support more diverse fish assemblages. Furthermore, environmental degradation results in the loss of ecomorphologically similar species, in which only those with distinct ecological requirements remain in the degraded streams. Therefore, conservation efforts that aim at sustaining environmental heterogeneity and mitigating urban land use do not only maintain the species’ diversity, but also the coexistence of ecomorphological similar fishes.
Journal Article
Payment for Ecosystem Services and the Water-Energy-Food Nexus: Securing Resource Flows for the Affluent?
Payment for Ecosystem Services (PES) is not only a prominent, globally promoted policy to foster nature conservation, but also increasingly propagated as an innovative and self-sustaining governance instrument to support poverty alleviation and to guarantee water, food, and energy securities. In this paper, we evaluate a PES scheme from a multi-scalar and political-ecology perspective in order to reveal different power dynamics across the Water-Energy-Food (WEF) Nexus perspective. For this purpose, we analyze the PES scheme implemented in the Hidrosogamoso hydropower project in Colombia. The paper shows that actors’ strongly divergent economic and political power is determinant in defining how and for whom the Nexus-related water, food, and energy securities are materialized. In this case, the PES scheme and its scalar politics, as fostered by the private/public hydropower alliance, are instrumental to guaranteeing water security for the hydropower scheme, which is a crucial building-block of Colombia’s energy security discourse. For this, the water and food securities of the adjacent, less powerful communities are sacrificed. Examining the on-the-ground politics of WEF Nexus is key to understanding their impact on equitable and sustainable governance of water, energy, and food in the everyday lives of millions of resource users. We conclude that politicizing the Nexus can help to trace both the flows of resources and the flows of power.
Journal Article
New insights into the decadal variability in glacier volume of a tropical ice cap, Antisana (0°29′ S, 78°09′ W), explained by the morpho-topographic and climatic context
We present a comprehensive study of the evolution of the glaciers
on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on
geodetic observations of aerial photographs and high-resolution satellite
images, we explore the effects of morpho-topographic and climate variables
on glacier volumes. Contrasting behaviour was observed over the whole
period, with two periods of strong mass loss, 1956–1964 (−0.72 m w.e. yr−1) and 1979–1997 (−0.82 m w.e. yr−1), and two periods with
slight mass loss, 1965–1978 (0.10 m w.e. yr−1) and 1998–2016 (−0.26 m w.e. yr−1). There was a 42 % reduction in the total surface area of
the ice cap. Individually, glacier responses were modulated by
morpho-topographic variables (e.g. maximum and median altitude and surface
area), particularly in the case of the small tongues located at low
elevations (Glacier 1, 5 and 16) which have been undergoing accelerated
disintegration since the 1990s and will likely disappear in the coming
years. Moreover, thanks to the availability of aerial data, a surging event
was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is
extremely rare in this region and deserves a dedicated study. Despite the
effect of the complex topography, glaciers have reacted in agreement with changes
in climate forcing, with a stepwise transition towards warmer and
alternating wet–dry conditions since the mid-1970s. Long-term decadal
variability is consistent with the warm–cold conditions observed in the
Pacific Ocean represented by the Southern Oscillation index.
Journal Article
Reduction of High-Chromium-Containing Wastewater in the Leaching of Pyritic Waste Rocks from Coal Mines
Coal is an abundant resource which can be used to produce low-cost energy; however, its usage causes great environmental damage. Before mineral coal can be used, it must be processed to remove coal tailings. These tailings contain pyrite and accumulate in large dumps, presenting significant environmental liabilities, such as acid mine drainage. Another industry that generates environmental liabilities is the chrome-plating industry, mainly because it produces hexavalent chromium (Cr6+) waste. The main aim of this work was to evaluate Cr6+ as a reduction agent in trivalent chromium (Cr3+) conversion in the leaching of coal-mine waste containing pyrite. Cr3+ is about 100 times less toxic than Cr6+ and can be easily removed from industrial effluents by alkaline precipitation. There are several sources of effluents containing Cr6+—a compound which is known worldwide to be toxic, carcinogenic, and mutagenic. A leaching and treatment device was developed and tested for waste treatment. The results indicated that the developed treatment system reduced 100% of Cr6+ to Cr3+ through pyrite leaching in a Cr6+ wastewater sample from the electroplating industry. In addition, the chromium sludge resulting from the treatment process, after calcination, was tested in a ceramic glaze as a pigment and, when compared with an industrial pigment, showed similar mineralogical characteristics.
Journal Article