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The use of renewable, bio-based fuels has become increasingly widespread in recent years, with a major example being biodiesel, a bio-derived alternative to Number 2 diesel fuel. The increased usage of biodiesel gives rise to an augmented need to understand its tribological effects on critical engine components. This study focused on determining the tribological performance of soybean-based B100 (i.e., pure) biodiesel within a fuel injector with varying oscillating frequency by performing a series of linear reciprocating tribological tests of biodiesel-lubricated interfaces with varying reciprocating frequency. Comparison of friction coefficient variation with reciprocating frequency indicated a transition from boundary lubrication to hydrodynamic lubrication as the frequency increased, while hysteresis loop and energy loss observations showed a transition between full stick and partial slip contact with increasing frequency. However, observations of induced wear showed the wear to increase with increasing frequency, most likely due to the augmented number of sliding cycles as well as an increased degree of interfacial slip. 相似文献
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Whilst there have been numerous categorisations of high-rise buildings according to their function, architectural style, height or structural strategy, historically little work has been undertaken to classify them based on factors affecting their energy performance — their shape and form, façade, attitude to natural lighting, ventilation strategies, etc. These factors have been influenced by regulatory changes, developments in technology and materials, changes in architectural thinking and economic and commercial drivers. Developments such as the New York Zoning Law of 1916, the postwar innovations in curtain wall façades and the energy crises of the 1970s have all impacted on the way tall buildings of the time were designed and operated. These events also had a significant impact on the quantity of energy and the way in which it was consumed in tall buildings of the time. This paper examines the history of energy use in tall buildings, from their origins in North America in the late nineteenth century to the present day. In doing so, it categorises tall buildings into five chronological ‘generations’, based on their energy consumption characteristics. 相似文献
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Gianoglio Dario Ciftci Nevaf Armstrong Sarah Uhlenwinkel Volker Battezzati Livio 《Metallurgical and Materials Transactions A》2021,52(9):3750-3758
Metallurgical and Materials Transactions A - Gas atomization is the most used powder production technique since it provides good control on particles shape, surface oxidation and dimension. It is a... 相似文献
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Dario Cavallo Lorenza Gardella Giuseppe Portale Alejandro J. Müller Giovanni C. Alfonso 《Polymer》2014
Isotactic poly(1-butene) (i-PBu) is a polyolefin of industrial relevance which exhibits an interesting polymorphism. Upon cooling from the relaxed melt at atmospheric pressure, a tetragonal phase (Form II) develops. However, being metastable, this structure slowly evolves upon aging in the stable trigonal modification (Form I). Another trigonal modification, denoted Form I′, can also crystallize directly from the melt if proper conditions are met, e.g., high pressure, low tacticity, ultrathin samples etc. In this work, we aim to verify whether, by acting on the nucleation stage via a proper thermal history, the direct formation of the trigonal polymorph from the melt in a bulk sample is possible. Nucleation of i-PBu has been tailored by means of the self-nucleation technique, imposed on previously aged samples (Form I). DSC and temperature-resolved WAXS show that different crystallization pathways can be observed, depending on the residual concentration of Form I self-nuclei. With decreasing self-nucleation temperature we first encounter “cross-nucleation” of the tetragonal crystal on trigonal nuclei, followed by concomitant crystallization of Form II and Form I′ and eventually the sole formation of the trigonal modification (Form I′). 相似文献
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Alessandro Marchioni Roberto Tonelli Alessandro Andreani Gaia Francesca Cappiello Matteo Fermi Fabiana Trentacosti Ivana Castaniere Riccardo Fantini Luca Tabbì Dario Andrisani Filippo Gozzi Giulia Bruzzi Linda Manicardi Antonio Moretti Serena Baroncini Anna Valeria Samarelli Massimo Pinelli Giorgio De Santis Alessandro Stefani Daniele Marchioni Francesco Mattioli Enrico Clini 《International journal of molecular sciences》2022,23(5)
Laryngotracheal stenosis (LTS) is a complex and heterogeneous disease whose pathogenesis remains unclear. LTS is considered to be the result of aberrant wound-healing process that leads to fibrotic scarring, originating from different aetiology. Although iatrogenic aetiology is the main cause of subglottic or tracheal stenosis, also autoimmune and infectious diseases may be involved in causing LTS. Furthermore, fibrotic obstruction in the anatomic region under the glottis can also be diagnosed without apparent aetiology after a comprehensive workup; in this case, the pathological process is called idiopathic subglottic stenosis (iSGS). So far, the laryngotracheal scar resulting from airway injury due to different diseases was considered as inert tissue requiring surgical removal to restore airway patency. However, this assumption has recently been revised by regarding the tracheal scarring process as a fibroinflammatory event due to immunological alteration, similar to other fibrotic diseases. Recent acquisitions suggest that different factors, such as growth factors, cytokines, altered fibroblast function and genetic susceptibility, can all interact in a complex way leading to aberrant and fibrotic wound healing after an insult that acts as a trigger. However, also physiological derangement due to LTS could play a role in promoting dysregulated response to laryngo-tracheal mucosal injury, through biomechanical stress and mechanotransduction activation. The aim of this narrative review is to present the state-of-the-art knowledge regarding molecular mechanisms, as well as mechanical and physio-pathological features behind LTS. 相似文献
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聚酯瓶使用的大量增加使得全世界范围内对于作为替代原生材料的二次原料——再生聚酯瓶片的回收及使用产生愈加浓厚的兴趣。 相似文献
40.
Soft bottom macrobenthos at a station located off Cesenatico (Emilia Romagna, Northern Adriatic Sea) was investigated seasonally for six years from July 1996 to July 2002. Species composition and abundance of the community have been studied in relation to fluctuation in the water environment parameters, sediment texture patterns and mucilage, that occurred mainly in the water column at the study site. Three major Po river flow peaks occurred in November 1996, October 2000 and May 2002; after these events the community was reduced to minimum abundance values (total density<2000 individuals m(-2)). In the period between the first two episodes the river discharge remained rather low and conditions of increased salinity, lower nutrients and chl a and good oxygen saturation were experienced. The fossorial Crustacean Ampelisca diadema became dominant in the community between the first two river flow events, reaching maximum density of 10,200 individuals m(-2) and substituting the bivalve Corbula gibba, indicator of sediment instability. Species richness increased in the same period. The role of Ampelisca as a facilitator in structuring the community is discussed. Corbula gibba never recovered to initial densities, apart from an abundance peak that occurred in the summer of 2000. Faunal composition seemed to evolve slowly towards a higher degree of structural complexity (positive trend in diversity and evenness index). In the study site near-bottom mucilage events occurred in the summers of 1997, 1998, 2002; they appeared uncorrelated with the observed changes in the community structure. Multivariate analysis of community structure (MDS, ANOSIM) illustrates that community changes in this station are driven mainly by hydrographical conditions influencing sediment texture patterns and trophic resources for the benthos. 相似文献