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Levers of logistics service providers' efficiency in urban distribution
No full textThis paper identifies the most important factors that influence the productivity of the urban fleet of a Logistics Service Provider (LSP). Through a regression analysis on a dataset from distribution warehouses of a single LSP, three main levers are shown to have significant impacts on productivity, namely the network design, the vehicle loading strategy, and the business environment wherein the operations are carried out. This paper contributes to bridge the gap about the lack of works addressing the efficiency of LSPs operating in urban areas, by performing a detailed empirical analysis instead of taking an aggregated company perspective
Italian railway stations heritage
No full textThe railway station represents the most advanced product of the architectural and technical culture of the age in which it was built. Nevertheless, the heritage of the railway stations can be considered as rather fragile. The knowledge of the construction history of these building is important in order to preserve the compositive values and the innovative technical solutions embedded in the building itself, particularly in case of a restoration or a complete renewal. The article aims to illustrate how the Italian railway stations have been designed and built throughout the years. The study focuses first of all on the railway stations which marked the beginning of the railway lines such as Torino Porta Nuova and Milano Centrale, which can be considered an example of the splendour achieved by the railway stations before the Second World War. Secondly the study analyses the new railway stations which are the starting point for the high speed railway lines such as Torino Porta Susa and Roma Tiburtina. The article dwells not only on the evolution of the architectonical language and of the layout of the station, but it focuses also on the structural scheme of the roofing solutions, which in many cases represent the true element of modernity
A stochastic approach to slope stability analysis in bimrocks
No full textBimrocks (block-in-matrix rocks) are defined as heterogeneous mixtures of hard rocks surrounded by a matrix of finer texture. A common practice when planning engineering works in these challenging materials is to take into account only the strength and deformation properties of the weaker matrix. However, as proved by many case histories recorded in the literature, such a simplified assumption can lead to incorrect results and, consequently, to unexpected difficulties and instability problems during construction works. The aim of this paper was to investigate slope stability in bimrocks using both finite element (FEM) and limit equilibrium (LEM) methods. More than 90 2D stability analyses were performed on slope models with the same geometry and with block proportions varying between 0% (matrix-only) and 70%. A stochastic approach was introduced in order to consider the inherent spatial and dimensional variability of rock inclusions. To this aim, a specific Matlab routine, performing numerical Monte Carlo simulations, was implemented. The code generates populations of 2D blocks with random sizes and positions within the slope models, according to specific statistical rules and given block contents. To achieve a statistical validity of the results, ten extractions and, hence, ten stability analyses were performed for each block proportion considered. Two empirical strength criteria available in the literature were also applied to the bimrock slope models by way of comparison. These criteria assume bimrocks to be homogeneous and isotropic masses with strength parameters that depend on their block contents and matrix strength. The effects of block proportions on safety factors, volumes involved and failure surfaces tortuosity provided by the different methods are discussed in detail. The findings of this study strongly suggest that bimrocks should be treated as heterogeneous materials, in order to avoid potential inaccuracies caused by neglecting the presence of blocks at the design stage. Furthermore, the benefits of using a stochastic rather than a deterministic approach to perform slope stability analyses in these heterogeneous materials is highlighted
Earth pressure on shield excavation face for pipe jacking considering arching effect
No full textPipe jacking is often used to install pipelines in congested urban areas or river crossings. The applied jacking force needs to be greater than the frictional resistance along the pipe and the face resistance. Lubricant slurries are usually employed to minimize the frictional resistance. Therefore, it is critical to estimate earth pressures acting on shield excavation face correctly. In this paper, the original Protodyakonov's arch model is modified to calculate the vertical pressure on deeply buried pipes. For shallow burial depth less than 5 m, the Terzaghi arching model is still applicable to estimate the vertical pressure. The soil prism in front of excavation face is divided into different zones to establish the force equilibrium. The calculated earth pressure is applied on top of soil wedges. The proposed analytical solution can analyze the stability of vertical and inclined excavation faces considering the influence of three-dimensional arching effect, as well as the contribution of soil cohesion. In the end, the effectiveness of the developed design framework is assessed by comparing calculations with experimental measurements of earth pressures on excavation face
Compact Surfaces with No Bonnet Mate
No full textThis note gives sufficient conditions (isothermic or totally nonisothermic) for an immersion of a compact surface to have no Bonnet mate
A new proposal for fusing individual preference orderings by rank-ordered agents: A generalization of the Yager's algorithm
No full textExploiting clustering algorithms in a multiple-level fashion: A comparative study in the medical care scenario
No full textClustering real-world data is a challenging task, since many real-data collections are characterized by an inherent sparseness and variable distribution. An appealing domain that generates such data collections is the medical care scenario where collected data include a large cardinality of patient records and a variety of medical treatments usually adopted for a given disease pathology. This paper proposes a two-phase data mining methodology to iteratively analyze dierent dataset portions and locally identify groups of objects with common properties. Discovered cohesive clusters are then analyzed using sequential patterns to characterize temporal relationships among data features. To support an automatic classication of a new data objects within one of the discovered groups, a classication model is created starting from the computed cluster set. A mobile application has been also designed and developed to visualize and update data under analysis as well as categorizing new unlabeled records. A comparative study has been conducted on real datasets in the medical care scenario using diverse clustering algorithms. Results were compared in terms of cluster quality, execution time, classication performance and discovered sequential patterns. The experimental evaluation showed the eectiveness of MLC to discover interesting knowledge items and to easily exploit them through a mobile application. Results have been also discussed from a medical perspective
Passive heat transfer enhancement by 3D printed Pitot tube based heat sink
No full text3D printing, also referred to as Additive Manufacturing - AM in case of metal materials, allows to fabricate complex shaped parts and devices in a single step. Extreme flexibility of AM techniques could pave the way to a revolution in conceiving heat transfer devices in the near future. Along this way, we designed and fabricated by AM an innovative heat sink incorporating Pitot tubes for realizing passive heat transfer enhancement. Preliminary tests show that the proposed heat sink allows up to 98% heat transfer augmentation, as compared to conventional heat sinks. We hope this study will help in encouraging the community to explore novel approaches thus moving towards the design of new devices fully exploiting the 3D printing flexibility in the field of thermal engineerin
3D-printed microfluidics on thin poly(methyl methacrylate) substrates for genetic applications
No full textAdditive manufacturing techniques using three dimensional (3D) printing have been shown to be suitable for a wide range of applications. In this study, stereolithography (SLA) is applied to the field of microfluidic fabrication of lab-on-a-chip (LOC) devices. LOCs deal with different milli/microsized channels and chambers, which are the key features of the devices, so an appropriate manufacturing process should provide high precision as well as high versatility. In this work, the goal was to overcome the common drawbacks of 3D printing and multistep processes, by implementing multiple polymeric materials in the same printing process. Using a customized SLA machine, a novel process was developed to print microfluidic channels enclosed between two poly(methyl methacrylate) layers in a sandwichlike structure. For microfluidic walls, two distinct commercial resins with different properties were used. Once thermal and pressure resistance of the obtained LOCs were assessed, deoxyribose nucleic acid was amplified by polymerase chain reaction inside the microfluidic chambers. Test results indicated favorable mechanical and thermal resistance, as well as chemical compatibility with the assay reagents. Such observations suggest that this novel approach can be applied to 3D printing of customized microfluidics with embedded features