Search results for " Reliability."
showing 10 items of 551 documents
Heavy Gas Dispersion Modelling Over a Topographically Complex Mesoscale
2005
Potentially dangerous events involving heavy gas dispersion and their severe consequences have been largely publicized by the media. Simplified models have been widely applied to describe the effects of these accidents. However, most simplified models deal with flat terrain scenarios and are based on quite crude simplifications of the complex phenomenology involved. In this paper the possibility of simulating the dispersion of heavy gas clouds over a large topographically complex area (tens of km) by a general purpose computational fluid dynamics (CFD) code is investigated. The aim is that of setting up a tool able to produce a realistic description of such dispersion processes, whose resul…
Alfalfa crops amended with MSW compost can compensate the effect of salty water irrigation depending on the soil texture
2018
The availability of water resources of marginal quality such as drainage water or high-saltcontaining groundwater is turning into an important issue in Tunisia and other countrieswith scarce water resources. A pot experiment was carried out to evaluate plant produc-tion, nutrient content and heavy metal bioaccumulation in agricultural soils amended withMSW compost and irrigated with salty water, by using two different soil textures (clay andsandy). Salt water supply decreased plant dry yield in both soils. Salt stress had signifi-cantly reduction in plant biomass in sandy soil compared to those in clay soil (biomass ofdry weight is significantly higher in clay soil than those in sandy soil …
Blind recovery of sources for multivariate space-time random fields
2022
AbstractWith advances in modern worlds technology, huge datasets that show dependencies in space as well as in time occur frequently in practice. As an example, several monitoring stations at different geographical locations track hourly concentration measurements of a number of air pollutants for several years. Such a dataset contains thousands of multivariate observations, thus, proper statistical analysis needs to account for dependencies in space and time between and among the different monitored variables. To simplify the consequent multivariate spatio-temporal statistical analysis it might be of interest to detect linear transformations of the original observations that result in stra…
Some properties of local weighted second-order statistics for spatio-temporal point processes
2019
Diagnostics of goodness-of-fit in the theory of point processes are often considered through the transformation of data into residuals as a result of a thinning or a rescaling procedure. We alternatively consider here second-order statistics coming from weighted measures. Motivated by Adelfio and Schoenberg (Ann Inst Stat Math 61(4):929–948, 2009) for the temporal and spatial cases, we consider an extension to the spatio-temporal context in addition to focussing on local characteristics. In particular, our proposed method assesses goodness-of-fit of spatio-temporal models by using local weighted second-order statistics, computed after weighting the contribution of each observed point by the…
Handling the epistemic uncertainty in the selective maintenance problem
2020
Abstract Nowadays, both continuous and discontinuous operating systems require higher and higher reliability levels in order to avoid the occurrence of dangerous or even disastrous consequences. Accordingly, the definition of appropriate maintenance policies and the identification of components to be maintained during the planned system’s downtimes are fundamental to ensure the reliability maximization. Therefore, the present paper proposes a mathematical programming formulation of the selective maintenance problem with the aim to maximize the system’s reliability under an uncertain environment. Specifically, the aleatory model related to the components’ failure process is well known, where…
Improved GNSS positioning exploiting a vehicular P2P infrastructure
2010
This paper considers the possibility to exploit external altitude measurements to improve the performance of a Kalman based GNSS receiver. The altitude measurements are provided by means of a peer to peer network, that is supposed to be based on the evolution of the 802.11 standard for the vehicular environment, namely the WAVE (802.11p). The performance of such a system are investigated for different characteristics of the aiding measurement and for a different number and disposals of the aiding peers. The aiding measurement is obtained starting from the altitude measurements that the other peers in the network send to the aided user. The experiments highlight the need for a parameter that…
MECANISMOS DE COORDINACIÓN ESTRUCTURAL, NO ESTRUCTURAL E INFORMAL. PROPUESTA Y VALIDACIÓN DE ESCALAS DE MEDIDA / STRUCTURAL, NON- STRUCTURAL AND INFO…
2008
El presente trabajo tiene como objetivo diseñar y validar escalas para medir diversos mecanismos de coordinación estructural, no estructural e informal. Los primeros están vinculados a puestos u órganos específicos, y nos referimos al diseño de redes, equipos de proyecto y desarrollo, y equipos de trabajo. Los mecanismos de coordinación no estructural sirven de complemento a los anteriores. En este grupo se encuentran la normalización de procesos de trabajo, de habilidades y de resultados. Por último, los mecanismos de carácter informal son el esfuerzo de socialización y la adaptación mutua. Tras la generación de una batería de 43 ítems, se han comprobado sus propiedades psicométricas: fiab…
QUALITY ATTRIBUTES, PECTOLYTIC ENZYME ACTIVITIES AND PHYSIOLOGICAL CHANGES DURING POSTHARVEST RIPENING OF NECTARINE
1996
The postharvest ripening at 20C and 90-95% RHfor 10 days of 'Armking' nectarine grown in a greenhouse was investigated over two seasons. Firmness, titratable acidity, ascorbic acid, pH and maturity index were all adequate to stablish the rate ofripening. However, soluble solids content and reducing and non-reducing sugars showed no significant changes. It took about 10 days for very early ripening fruit (100 g weight and 82 N firmness) and 6 days for normal early ripening fruits (115 g weight and 46 N firmness), both harvested at preclimacteric stage, to become eating ripe (near 20 N). Total weight loss and decay after 10 days was approximately 11%. During ripening there was a temporal coin…
Design of the EBE-ST Questionnaire among Nursing Students: Multicenter Study from Eight Universities in Spain
2021
Background: Twenty years after the degree in nursing was introduced in Spain, the subject of evidence-based nursing is still unstructured and unestablished in most faculties. Moreover, there are hardly any rigorous studies at a national level that evaluate the current state of this competence in our faculties. Understanding the starting point is essential for the curricular design to ensure that evidence-based practice is implemented among future professionals. Aim: To design and validate an evidence-based nursing competency questionnaire for fourth-year nursing students. Methods: A specific questionnaire was developed and validated (EBE-ST). A cross-sectional survey design with psychometri…
Smartphone-based bridge monitoring through vehicle-bridge interaction: analysis and experimental assessment
2022
AbstractIn this study, the results of a vast experimental campaign on the applicability of a smartphone-based technique for bridge monitoring are presented. Specifically, the vehicle–bridge interaction (VBI)-based approach is exploited as a cost-effective means to estimate the natural frequencies of bridges, with the final aim of possibly developing low-cost and diffused infrastructure monitoring system. The analysis is performed using a common hybrid vehicle, fully equipped with classical piezoelectric accelerometers and a smartphone MEMS accelerometer, to record its vertical accelerations while passing over the bridge. In this regard, the experimental campaign is carried out considering t…