1,357,068 research outputs found
Short lifetime components in the relaxation of boron acceptors in silicon
No full textThe data is that described in 'Short lifetime components in the relaxation of boron acceptors in silicon’, K. Saeedi et al, Physical Review B (2018).
The data consists of the probe transmission as a function of time delay in each case. The different experiments are labelled according to the figure in which they occur in the main paper. The data are raw and have not been smoothed or otherwise processed.
The data is in an Origin file format. Please contact the author for data in other formats.</p
A world dataset on the geographic distributions of Solenidae razor clams (Mollusca: Bivalvia)
Get PDFBackground: Using this dataset, we examined the global geographical distributions of Solenidae species in relation to their endemicity, species richness and latitudinal ranges and then predicted their distributions under future climate change using species distribution modelling techniques (Saeedi et al. 2016a, Saeedi et al. 2016b). We found that the global latitudinal species richness in Solenidae is bi-modal, dipping at the equator most likely derived by high sea surface temperature (Saeedi et al. 2016b). We also found that most of the Solenidae species will shift their distribution ranges polewards due to global warming (Saeedi et al. 2016a). We also provided a comprehensive review of the taxon to test whether the latitudinal gradient in species richness was uni-modal with a peak in the tropics or northern hemisphere or asymmetric and bimodal as proposed previously (Chaudhary et al. 2016).
New information: This paper presents an integrated global geographic distribution dataset for 77 Solenidae taxa, including 3,034 geographic distribution records. This dataset was compiled after a careful data-collection and cleaning procedure over four years. Data were collected using field sampling, literature and from open-access databases. Then all the records went through quality control procedures such as validating the taxonomy of the species by examining and re-identifying the specimens in museum collections and using taxonomic and geographic data quality control tools in the World Register of Marine Species (WoRMS) and the r-OBIS package (Provoost and Bosch 2017). This dataset can thus be further used for taxonomical and biogeographical studies of Solenidae
Long-term Dietary n3 Fatty Acid Prevents Aging-related Cardiac Diastolic and Vascular Dysfunction
No full textAbstractAims: The prevalence of left ventricular (LV) diastolic and vascular dysfunction increases with age, eventually leading to heart failure with preserved ejection fraction (HFpEF). A preventive strategy is an unmet medical need. We and others reported previously on the beneficial effects of omega-3 fatty acid alpha linolenic acid (ALA) on cardiovascular disorders in animal models and translational studies. We now investigate whether long-term dietary ALA could prevent LV diastolic dysfunction and vascular aging in a murine model.Methods and Results: Wild-type C57BL/6J mice were fed a chow or ALA diet for 12 months, starting at 6 months of age. Here, we show that aged (~18 months) mice recapitulate major hallmarks of HFpEF, including LV diastolic dysfunction with preserved ejection fraction, impaired vascular function, cardiac fibrosis, arterial stiffening and inflammation, as well as elevated B-type natriuretic peptide (BNP). Long-term ALA supplementation upregulated the mitochondrial tricarboxylic acid enzyme Idh2 and the antioxidant enzymes SOD1 and Gpx1. It also counteracted inflammation and ECM remodeling by regulating NF-κB and in turn significantly reducing fibrosis biomarkers MMP-2/TGF-β in both cardiac and vascular tissues obtained from aged mice. These mechanisms emphasize the beneficial preventive effects of ALA on LV diastolic dysfunction, impaired vasorelaxation, cardiac fibrosis, inflammation and arterial stiffening in aged mice, considered as hallmarks of HFpEF.Conclusions: We provide evidence and mechanistic insight on how long-term ALA supplementation is a successful strategy to prevent the development of age-related diastolic and vascular dysfunction
Dielectric properties of modified epoxy resin systems: A novel approach for developing materials for new generation technologies
No full textEpoxy resins are thermosetting polymers that features attractive electrical, thermal and mechanical properties, which made them widely used as a primary insulating material in many electrical applications. Over the past decade, the increase in the energy demands led to increase in the size and change in the operation conditions of the electrical equipments, where their insulating materials are expected to withstand the continuous shift in the operation conditions. Consequently, polymer nanocomposite materials were introduced as a potential solution for producing high-performance insulators, and tailor the properties that effect field distribution in epoxy based materials. Later on, it was reported that some of the fillers are suggested to cause deterred properties, for example, some nano-fillers were difficult to disperse in the host material, which limited the advantages of these nanocomposites. An alternative and/or complementary approach is to use liquid functional network modifiers FNM. These FNM contains epoxide groups within their chemical structure which allows the FNM to contribute to the curing process, thus, the FNM modifier become incorporated in the cured network structure of the modified systems and influence the final properties of the system.This research was set out to provide insights into the effect of functional network modifiers on the properties of epoxy resin systems with the hope of engineering novel epoxy based insulating material for the future. While using liquid functional network modifiers FNM approach has previously been used as a means for altering the mechanical properties of epoxy resins. This research investigated this approach in depth, and also the first study that explores this approach as means of integrating different functional groups into a thermosetting polymers, in order to effectively customise its properties. The research started by providing a background for epoxy curing mechanisms and the method used for modifying the properties of epoxy resin systems reported in the literature. In addition to review of studies investigated the concept of voltage stabilisers that is based on which an explanation or interpretation was provided for the body of knowledge about FNM behaviour. Prior to investigating the effect of any FNM on the properties of the modified systems, the effect of the of the FNM on the stoichiometric ratio of epoxy resins was established by running a series of experiments (FTIR, DSC, dielectric properties and AC breakdown strength of the modified systems). These experiments were carried out on a simple amine-cured epoxy resin system by using compensated and uncompensated systems. In the compensated systems, the FNM was added by precisely calculating the number of the epoxide groups being supplied by the FNM, where the equivalent number of epoxide groups provided by the resin are removed, ensuring the same number of epoxide groups present in the system after the addition of the FNM. While, in the uncompensated systems the FNM was added without changing the stoichiometry of the system. By comparing the variation in the properties of the compensated and uncompensated systems, it was concluded that the stoichiometric ratio of the FNM plays a vital role in determining the properties of the final material. In addition, the effect of the FNM on the Tg, dielectric spectroscopy and the breakdown strength is found to be attributed to several factors. In these experiments, the most dominant factor was the structure of the functional groups of the FNM. By investigating the effect of the chemical structure of the FNM on the FTIR, DSC, dielectric properties, AC breakdown strength and DC conductivity of epoxy resin systems modified by the inclusion of varied concentrations of different FNM modifiers, it was found that the properties of the modified systems are influenced by both the chemical structure of the functional groups and the concentration of the FNM in the system. For example, the use of liquid epoxy resin and low concentration FNM (4%) suggested to produce FNM modified epoxy resins with improved properties compared to that of the neat epoxy, which is suggested to offer a new means of engineering novel materials to meet current and future needs in an adaptable way. This research also investigated the effect of the curing mechanisms on the behaviour of the modified systems. It was found that the presence of the functional network modifier influenced the chemical, thermal and electrical properties of the amine and anhydride cured systems. This was followed by a a detailed analysis study of the molecular origin and the activation energy of each relaxation process. This analysis was needed because of the lack detailed analysis of the dielectric behaviour of anhydride cured resins in literature. Also, the presence of the FNM made prediction of the behaviour more challenging. The study analysed the temperature dependent dielectric properties along with Havriliak-Negami deconvoluted peaks, as well as the Arrhenius plots and the associated activation energies of the different molecular relaxations. It was concluded that the type of the functional group of the FNM plays a vital role in determining the network topology and the dielectric molecular dynamics of the final material.The work reported in this research proves that functional network modifiers constitute a complementary and alternative approach for nanotechnology for designing materials with controlled dielectric properties. The systems researched, combined with the applied research method and the described experimental setup provides a complete guide for future studies to replicate the results and experiment with different FNM combinations
An innovative hybrid strategy for structural health monitoring by modal flexibility and clustering methods
No full textStructural health monitoring is usually implemented by model-driven or data-driven methods. Both of them have their advantages and disadvantages. This article proposes an innovative hybrid strategy as a combination of model-driven and data-driven approaches to detecting and locating damage in civil structures. In this regard, modal flexibility matrices of the undamaged and damaged conditions are initially derived from their modal frequencies and mode shapes. Subsequently, the discrepancy between these matrices is proposed as a damage-sensitive feature. To increase damage detectability and localizability, the modal flexibility discrepancy matrix is expanded by the Kronecker product and then converted into a vector by a simple vectorization algorithm yielding vector-style feature samples. To detect and locate damage, this article introduces the k-medoids and density-based spatial clustering of applications with noise techniques. The vector-style feature samples are incorporated into these clustering methods to obtain two different damage indices including the direct clustering outputs and their Frobenius norms. The great novelty of this article is to develop an innovative hybrid strategy for damage detection and localization under noise-free and noisy conditions so that the damage-sensitive feature is obtained from a model-driven scheme and the decision-making is carried out by a data-driven strategy. A shear-building frame and the numerical model of the ASCE benchmark structure are used to validate the accuracy and performance of the proposed methods. Results demonstrate that the hybrid strategy presented here is influentially able to detect and locate damage in the presence of noisy modal data
On the design of the structure of epoxy resin networks
No full textThe molecular structure of epoxy resin plays a vital role in defining the properties of epoxy-based insulation. The reactions between the epoxy terminated resin and the hardener, result in the formation of the cured system. In the case of amine hardeners, a node is generated due to relatively simple reactions between the primary and secondary amine of the hardener and the epoxide groups of the resin. On the other hand, in the case of anhydride based hardeners, both etherification and esterification reactions take place to form the cured material. Our previous work has revealed that the modification of an amine cured system using an epoxy-based diluent can result in the formation of a branched molecular network, which can lead to increased breakdown strength of the system. In this study, the design of a molecular structure for both amine and anhydride cured systems with increased electrical strength is suggested by adopting the hypothesis of the branched molecular structure. Two epoxy resin based systems (amine and anhydride cured) were modified using a reactive diluent featuring at least one epoxide group within its chemical structure. Dielectric spectroscopy and breakdown strength measurements were used to study the behavior of the manufactured systems. The dielectric data obtained from the samples indicate that the permittivity is strongly affected by the functional group of the reactive diluent, while the breakdown strength depended on both the percent of added diluent and the functional group consequently introduced. By using a precisely designed three-component epoxy system, it has been possible to control the properties of the resulting system; materials with increased breakdown strength have been produced. This approach is of high potential importance because it may allow materials to be designed with controlled properties to suit particular applications.</p
PIK887818 Supplemetal Material - Supplemental material for A new robust combined control system for improving manoeuvrability, lateral stability and rollover prevention of a vehicle
No full textSupplemental material, PIK887818 Supplemetal Material for A new robust combined control system for improving manoeuvrability, lateral stability and rollover prevention of a vehicle by Mohammad Amin Saeedi in Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics</p
Optimizing energy density in dielectric elastomer generators: a reliability-dependent metric
No full textDielectric elastomer generators (DEGs) are soft transducers capable of converting mechanical energy into electrostatic energy. Increasing the mechanical stretch amplitude and the electric field imposed to the DEG leads to higher energy conversion at the cost of a reduced lifetime. Here, mechanical fatigue and electrical degradation were assessed on a silicone-based DEG, and the outcome was used to build an electro-mechanical reliability model. A novel metric, termed levelized energy density, has been introduced to carefully balance the conflicting objectives of high energy output and long-term reliability. Through a multi-dimensional anaylsis of this index, the optimal operating parameters (stretch amplitude and electric field) that maximize energy conversion can be derived. Energy densities reported in literature are generally obtained after pushing the DEG close to their intrinsic limits for a limited number of cycles. In our approach, more realistic values in the endurance domain are presented, which typically leads to a 9-fold decrease in energy density for a design life of 1 million cycles. This article not only addresses the challenge of optimizing DEG performance but also emphasizes the importance of considering realistic operational conditions to enhance reliability, ultimately contributing to the practical and sustainable deployment of these soft transducers in various applications.</p
ICT Platforms and the Restaurant Business in Times of Covid-19: The Case of Italy
No full textThe Covid-19 pandemic impacted the tourism industry worldwide.
Measures taken by Governments to contain the contagion and limit social relations
have had a significant impact also on foodservice. Starting in May 2020, Italian
restaurants can only operate by reservation and tracking the identity of customers.
ICT plays a fundamental role in supporting these changes, transforming barrier into
opportunity and allowing the collection of a large amount of data on consumer
behavior. Such data should be managed through a strategic approach to better
optimize management. This paper presents a longitudinal study on the use of ICT
platforms by Italian restaurant managers. The findings reveal how new rules
imposed by Government changed restaurant managers’ attitude towards technology.
In 2017 they showed reticence towards technology, not employed in a strategic
way; today everyone uses ICT to improve business. The pandemic fostered a
technological leap of many foodservice managers. Theoretical and practical
implications for researchers and restaurateurs are discussed
Balancing energy conversion and long-term reliability of dielectric elastomer generators
No full textDielectric elastomer generators (DEG) are soft transducers capable of converting mechanical energy into electrostatic energy. Increasing the mechanical stretch amplitude and the electric field imposed to the DEG leads to higher energy conversion on one hand, but at the cost of a reduced lifetime on the other hand. Here, mechanical fatigue and electrical limits are assessed on a silicone-based DEG and the outcome is used into an electro-mechanical reliability model. The operating parameters (stretch amplitude and electric field) which maximize the energy conversion are obtained from a multi-dimensional optimization approach which gives the best compromise between energetic cycles and long-term reliability. Energy densities reported in the literature are often obtained by pushing the DEG on the knife-edge of their intrinsic capabilities for a limited number of cycles . In contrast, our analysis presents more realistic values in the endurance domain, leading to a substantial reduction of the practical performance that can be achieved
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