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911.
Hazard based models for freeway traffic incident duration 总被引:1,自引:0,他引:1
Ahmad Tavassoli Hojati Luis Ferreira Simon Washington Phil Charles 《Accident; analysis and prevention》2013
Assessing and prioritising cost-effective strategies to mitigate the impacts of traffic incidents and accidents on non-recurrent congestion on major roads represents a significant challenge for road network managers. This research examines the influence of numerous factors associated with incidents of various types on their duration. It presents a comprehensive traffic incident data mining and analysis by developing an incident duration model based on twelve months of incident data obtained from the Australian freeway network. Parametric accelerated failure time (AFT) survival models of incident duration were developed, including log-logistic, lognormal, and Weibul—considering both fixed and random parameters, as well as a Weibull model with gamma heterogeneity. The Weibull AFT models with random parameters were appropriate for modelling incident duration arising from crashes and hazards. A Weibull model with gamma heterogeneity was most suitable for modelling incident duration of stationary vehicles. Significant variables affecting incident duration include characteristics of the incidents (severity, type, towing requirements, etc.), and location, time of day, and traffic characteristics of the incident. Moreover, the findings reveal no significant effects of infrastructure and weather on incident duration. A significant and unique contribution of this paper is that the durations of each type of incident are uniquely different and respond to different factors. The results of this study are useful for traffic incident management agencies to implement strategies to reduce incident duration, leading to reduced congestion, secondary incidents, and the associated human and economic losses. 相似文献
912.
913.
Navaneethan Muthuswamy Jose Luis Gomez de la Fuente Dung T. Tran John Walmsley Mikhail Tsypkin Steinar Raaen Svein Sunde Magnus Rønning De Chen 《International Journal of Hydrogen Energy》2013
The present work presents a method to encapsulate pre-synthesised Ru nanoparticles (NPs) by Pt using a polyol method without capping agents at various pH values (6, 7, 8 and 10). The structural and surface properties of the catalysts were characterised using X-ray diffraction, transmission electron microscopy, CO stripping, and energy-dispersive X-ray spectroscopy. The studies suggest that the pH during encapsulation of Ru by Pt plays an important role in controlling of shell composition. A core–shell catalyst with an alloy shell was obtained at a pH of 6, whereas a monometallic Pt shell was obtained at a pH of 10. The core–shell catalysts gave higher steady-state current for methanol oxidation: 10-fold higher for alloy shells and 5-fold higher for Pt-enriched shells compared to the pure Pt catalyst. It is suggested that the highest catalytic enhancement of the core–shell catalysts is obtained through the bi-functional character that dominates the alloy shells rather than the ligand-effect-promoted Pt-enriched shells. 相似文献
914.
In this work a real automobile assembly line and the correspondent preassembly lines have been analyzed as a network of closed loops of machines decoupled by intermediate buffers. This work deals with some important aspects, which have still not been investigated in earlier literature, such as: machines processing pallets, which are not related to each other and depend on an external variable in a network with closed loops of machines and intermediate buffers, machines working at different cycle times in a network of closed loops of machines and intermediate buffers, machines working in both, stationary and transitory regime and the relationships between the cycle times of the machines in the stationary working regime in order to guarantee the production rate of the system. Finally how the transient results can be used to improve the performance of the system under certain working conditions is discussed. 相似文献
915.
Fernando Jiménez-Sáez Jon Mikel Zabala-Iturriagagoitia Jose Luis Zofío 《Scientometrics》2013,94(1):273-303
This paper evaluates to what extent policy-makers have been able to promote the creation and consolidation of comprehensive research groups that contribute to the implementation of a successful innovation system. Malmquist productivity indices are applied in the case of the Spanish Food Technology Program, finding that a large size and a comprehensive multi-dimensional research output are the key features of the leading groups exhibiting high efficiency and productivity levels. While identifying these groups as benchmarks, we conclude that the financial grants allocated by the program, typically aimed at small-sized and partially oriented research groups, have not succeeded in reorienting them in time so as to overcome their limitations. We suggest that this methodology offers relevant conclusions to policy evaluation methods, helping policy-makers to readapt and reorient policies and their associated means, most notably resource allocation (financial schemes), to better respond to the actual needs of research groups in their search for excellence (micro-level perspective), and to adapt future policy design to the achievement of medium-long term policy objectives (meso and macro-level). 相似文献
916.
917.
Irene Malpartida Maria Angeles Larrubia Vargas Luis J. Alemany Elisabetta Finocchio Guido Busca 《Applied catalysis. B, Environmental》2008,80(3-4):214-225
Pt–Ba–Al2O3 active and selective for NOx storage and selective reduction to N2 has been prepared and tested. Characterization of the parent Al2O3, Pt–Al2O3 and Ba–Al2O3 materials, as well as of Pt–Ba–Al2O3 catalyst in the oxidized, reduced and sulphated state has been performed by FT-IR spectroscopy of low-temperature adsorbed carbon monoxide and of adsorbed acetonitrile. XRD, TEM and XPS analyses have also been performed. Evidence for the predominance of Ba species, which are highly dispersed on the alumina support surface, and may be carbonated or sulphated, has been provided. Competitive interaction of Pt and Ba species with the surface sites of alumina has also been found. 相似文献
918.
María Jesús Ramos Vicente Jiménez Antonia Fúnez Amaya Romero Paula Sánchez José Luis Valverde 《Catalysis Letters》2008,125(3-4):220-228
In this work, the hydroisomerization of n-octane on mono and bimetallic beta agglomerated zeolite based catalysts was investigated. As the metal function, platinum and combinations with nickel and tin were studied. Test reactions were carried out at 10 bar and 290–410 °C. The bimetallic catalyst with the lowest amount of Ni yielded the greatest multibranched selectivity. 相似文献
919.
Rafael J. López-Bellido Juan E. Castillo Luis López-Bellido 《Nutrient Cycling in Agroecosystems》2008,80(2):121-130
A 3-year multi-site study was carried out on rainfed Vertisols under Mediterranean conditions in southern Europe to determine
the influence of the N fertilizer rate on soil nitrates, N uptake and N use efficiency in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. Durum Desf.) in rotation with sunflower (Heliathus annuus L.). Nitrogen fertilizer rates were 0, 100, 150 and 200 kg N ha−1 applied in equal proportions at sowing, tillering and stem elongation. The experiment was designed as a randomized complete
block with a split plot arrangement and four replications. Nitrogen harvest index (NHI), N uptake/grain yield (NUp/GY), N
use efficiency (NUE), N utilization efficiency (NUtE), N uptake efficiency (NUpE) and N apparent recovery fraction (NRF) were
calculated. Differences were observed in N use efficiency between the two modern bread wheat and durum wheat cultivars studied.
In comparison to durum, bread wheat displayed greater N accumulation capacity and a more efficient use of N for grain production.
While under N-limiting conditions, the behavior was similar for both wheat types. No difference was noted between wheat types
with regard to changes in soil residual
levels over the study period at the various sites. The 100-kg ha−1 N fertilizer rate kept soil nitrates stable at a moderate level in plots where both wheat types were sown. 相似文献
920.
Electrospun nanofibers of a degradable poly(ester amide). Scaffolds loaded with antimicrobial agents
Luis J. del Valle Manuel Roa Angélica Díaz María T. Casas Jordi Puiggalí Alfonso Rodríguez-Galán 《Journal of Polymer Research》2012,19(2):9792-13
Electrospinning conditions were evaluated to prepare micro/nanofibers of a biodegradable poly(ester amide) constituted by
L-alanine, 1,12-dodecanediol and sebacic acid. 1,1,1,3,3,3-Hexafluroroisopropanol appeared as the most appropriate solvent
to obtain fibers in a wide range of electrospinning conditions that allowed tuning the final diameter size. Fiber diameter
increased with the flow, distance between the needle tip and the collector and decreasing voltage, which made it possible
to obtain homogeneous fibers in the 1700–320 nm range. Fibers were loaded with antimicrobial agents like silver and chlorohexidine,
and the influence of agent concentration in the electrospinning solutions on the fiber diameter size was determined. The polymer
was able to crystallize during the electrospinning process, giving rise to a structure slightly different from that obtained
by solution crystallization and related to that attained after crystallization from the melt state. Addition of antimicrobial
agents had little effect on the degree of crystallinity, although it decreased slightly when chlorhexidine was employed. Scaffolds
prepared from the silver and chlorhexidine loaded samples supported cell adhesion and proliferation. Furthermore, a clear
and well differentiated antimicrobial effect against both Gram-positive (e.g. M. luteus) and Gram-negative (e.g. E. coli) bacteria was demonstrated. 相似文献