Fine-grained, local maps and coarse, global representations support human spatial working memory

While sensory processes are tuned to particular features, such as an object's specific location, color or orientation, visual working memory (vWM) is assumed to store information using representations, which generalize over a feature dimension. Additionally, current vWM models presume that different features or objects are stored independently. On the other hand, configurational effects, when observed, are supposed to mainly reflect encoding strategies. We show that the location of the target, relative to the display center and boundaries, and overall memory load influenced recall precision, indicating that, like sensory processes, capacity limited vWM resources are spatially tuned. When recalling one of three memory items the target distance from the display center was overestimated, similar to the error when only one item was memorized, but its distance from the memory items' average position was underestimated, showing that not only individual memory items' position, but also the global configuration of the memory array may be stored. Finally, presenting the non-target items at recall, consequently providing landmarks and configurational information, improved precision and accuracy of target recall. Similarly, when the non-target items were translated at recall, relative to their position in the initial display, a parallel displacement of the recalled target was observed. These findings suggest that fine-grained spatial information in vWM is represented in local maps whose resolution varies with distance from landmarks, such as the display center, while coarse representations are used to store the memory array configuration. Both these representations are updated at the time of recal

Probabilistic assessment of footbridge response to single walkers

Among the load scenarios considered for the serviceability assessment of human-induced footbridge vibration, is that of the transient action of a single pedestrian or a small group of pedestrians. Although such action is stochastic due to the variability of gait parameters, available Codes and Guidelines all assume it is deterministic and equal to that coming from the “worst pedestrian ever” for the given footbridge. This approach is sound from an engineering point of view but does not allow control of the probability of failure. The present work deals with a reliability-based procedure for the serviceability assessment of the footbridge peak characteristic accelerations due to pedestrian induced actions. Based on the results obtained incorporating the effects of the inter-subject variability of gait parameters and of the uncertainties in footbridge dynamic properties, a design response spectrum is proposed for both vertical and lateral vibrations. The proposed procedure lends itself for immediate Code implementation

Imparting superhydrophobic properties through janus wrinkled silica-gel particles

In nature, superhydrophobicity is associated with a number of possible evolutionary benefits that may be bestowed upon an organism, ranging from the prevention of encumbrance by water droplets, self-cleaning and removal of particulates and potential pathogens, and even to antimicrobial activity. Superhydrophobicity is a surface related property, where droplets of water easily roll-off without stickicking or wetting the surface and can be achieved through hierarchical textured and low surface tension materials. The interest in this kind of behaviour comes from the possibility of exploiting superhydrophobic surfaces for many applications in different field (medical devices, infrastructures, fabrics, transports, etc.). In this PhD project (granted by Procter & Gamble), superhydrophobic surfaces were chosen as possible solution of a company’s problem related to the difficulty in emptying of plastic dispensers containing viscous liquid products. Therefore, a possible solution was to render the plastic surface superhydrophobic to reduce the drag and help the easy-emptying of the dispensers. We developed a new type of particles that can impart a superhydrophobic behaviour to the applied substrate. Janus wrinkled silica-gel particles combine all the aspects that are necessary to achieve superhydrophobic surfaces: enabling formation of hierarchical roughness and low surface tension (without using any fluorinated molecule, not allowed in the dispensers manufacturing). Such particles were applied to substrates by drop-casting and dip-coating methods, and through a camera we monitored the behaviour of different water solutions on particles coatings. Superhydrophobic surfaces have been obtained possessing high values of water contact angle and very low values of contact angle hysteresis (2°) and roll-off angle values (1.8°), which are close to zero. These results have been interpreted based on the multiple scales of hierarchical roughness that has been constructed by deposition of the particles. This thesis is divided in five chapters. In chapter 1, superhydrophobicity and how nature and man exploit this surface property are described so as methods to achieve such behaviour. Then, 10 the easy-emptying issue is discussed and the use of Janus wrinkled silica-gel particles as possible solution is motivated. Chapter 2 collects the theoretical backgrounds of this multidisciplinary project. Indeed, production of Janus wrinkled silica-gel particles involve different techniques and methods from different branches of science. Superhydrophobicity is described from a theoretical point of view: models and parameters that characterize the wettability of surfaces with regards to liquids are reported. Sol-gel method is briefly described, paying attention to the mesoporous particles formation mechanism. In the end, Pickering emulsion formation, necessary for Janus particles production, is described. In chapter 3, all the synthetic procedures are reported. The chapter is divided in paragraphs that reflects the multi-step synthetic procedure. First the synthesis of wrinkled silica-gel particles, then the formation of colloidosomes by Pickering emulsification of wrinkled particles, wax and water. Subsequently, the surface functionalization for obtaining Janus wrinkled particles. The characterization techniques are described in chapter 4, together with the apparatus used in this work and the sample preparations related to such characterization techniques. We used microscopic techniques as SEM, TEM and AFM for monitoring the structures of particles (SEM, TEM), the hierarchical roughness of the coatings (SEM, AFM) and the Janus nature of the particles (TEM). DLS and Zeta potential measurements were used for monitoring particles size and stability, especially in surfactant dispersions, necessary for Pickering emulsion preparation. ATR and XPS allowed evaluating the presence of functional groups (ATR, XPS) after each functionalization. Chapter 5 collects all the results of Janus wrinkled silica-gel particles: from the particles synthesis, to colloidosomes formation through Pickering emulsion, their functionalization and the particles application as coating on different substrates. In the end, the wettability properties results are reported to verify the excellence of this approach achieving superhydrophobic behaviour by Janus wrinkled silica-gel particles coatings

Load-carrying capacity of compressed wall-like RC columns strengthened with FRP

The analytical prediction of the effectiveness of fiber-reinforced polymer (FRP) in the confinement of a rectangular reinforced concrete (RC) column with a high aspect ratio (wall-like) still has an uncertain solution. In this paper, a numerical investigation of the axial response of RC wall-like columns strengthened with FRP systems was developed. Analytical solutions proposed in the literature for the assessment of the axial load capacity were presented and compared with each other and with the available experimental results. Moreover, non-linear finite element analysis was carried out, and the results were discussed, providing a simple model for the assessment of the axial compressive strength of wall-like RC columns strengthened with FRP

Numerical Modelling of the MIT/NREL TLP Wind Turbine and Comparison with the Experimental Results

In this study, numerical analysis of a tension leg platform wind turbine is conducted and the responses with focus on surge motions and tendon tension are compared with available experimental test data. The main scope of the study is to establish the numerical model for which the damping coefficients for rigid-body motions are tuned based on the comparison of the sway free decay test results (natural periods and damping ratios) between the numerical and the experimental studies. The differences between the test model properties and the numerical model information have been discussed. Numerical model tuning with available test data resulted with relatively good accordance but also slight to moderate differences in the responses. These differences are credited for the uncertainties in the model testing and the solution methodology of the numerical model. Numerical study is under development with regular and irregular wave analyses and analyses including wind excitation

Spatial attention can be biased towards an expected dimension

A commonly held view in both exogenous and endogenous orienting is that spatial attention is associated with enhanced processing of all stimuli at the attended location. However, we often search for a specific target at a particular location, so an observer should be able to jointly specify the target identity and expected location. Whether attention can bias dimension-specific processes at a particular location is not yet clear. We used a dual task to examine the effects of endogenous spatial cues on the accuracy of perceptual judgments of different dimensions. Participants responded to a motion target and a colour target, presented at the same or different locations. We manipulated a central cue to predict the location of the motion or colour target. While overall performance in the two tasks was comparable, cueing effects were larger for the target whose location was predicted by the cue, implying that when attending a particular location, processing of the likely dimension was preferentially enhanced. Additionally, an asymmetry between the motion and colour tasks was seen; motion was modulated by attention, and colour was not. We conclude that attention has some ability to select a dimension at a particular location, indicating integration of spatial and feature-based attention. </jats:p

Feasibility analysis for floating offshore wind energy

Purpose The assessment of the economic feasibility of foating ofshore wind farms (FOWFs) plays an important role in the future possible spreading of this challenging technology in the wind power industry. The use of specifc economic analyses is fundamental to point out the potential of FOWFs and to sustain their technical value. Within this topic, the implementation of the FOWF life cycle cost model and producibility analysis in a geographic information system is developed, with the aim of carrying out a feasibility analysis at the territorial scale, for diferent types of foater. Moreover, a simplifed model for a quick life cycle cost assessment is proposed and calibrated. Methods The available cost model is frst validated comparing the costs of FOWFs based on diferent foaters (Semi-Submersible Platform—SSP, Spar Buoy—SB and Tension Leg Platform—TLP) with corresponding results available in the literature. Then, it is implemented in QGIS to be used for territorial-scale analyses and sensitivity analyses of the cost parameters. A feasibility analysis is developed through the main fnancial parameters. Finally, the results are then&nbsp;used to calibrate a simplifed version of the cost model that depends on three main parameters, namely distance to shore, distance from the port of operation and bathymetry. Results and discussion The FOWF cost values are found to be in good agreement with those coming from analytical methods similar to the one from the authors. However, some discrepancies with those based on average costs are observed. Then, the results of the sensitivity analysis are presented as life cycle cost maps, giving an overall picture of the variation of the total cost of FOWF installations on a reference domain. The results show that among the three types of foaters considered here, the SSP proved to be the most promising one, giving lower costs than the SB and the TLP. Moreover, a good agreement between the results in terms of total cost of FOWFs calculated with the analytical and simplifed models for SSPs, SBs and TLPs is observed. Finally, the feasibility analysis showed that the fnancial parameters are more infuenced by the wind speed than by the cost of the farm. Conclusions The paper aims to provide guidance on how to carry out feasibility analyses of a specifc site for FOWF installation, thus supporting decision-making procedures. The approach and the results presented here are meant for use in the early stage of the decision-making process, as a tool for the assessment of the economic feasibility of FOWFs installation

The Relationship between Wind Pressure and Pressure Coefficients for the Definition of Wind Loads on Buildings

Wind induced pressures on buildings are the product of a velocity pressure and a pressure coefficient. The way in which these two quantities are calculated has changed over the years, and Design Codes have been modified accordingly. This paper tracks the evolution of the approach to wind loading of buildings from the practice in the 1950s, mainly referring to the Swiss Code SIA, to the most recent advances including probabilistic methods, internet databases, and advanced modelling of meteorological phenomena

Seismic Retrofit of a Multispan Prestressed Concrete Girder Bridge with Friction Pendulum Devices

The paper deals with the proposal and application of a procedure for the seismic retrofit of an existing multispan prestressed concrete girder bridge defined explicitly for the use of friction pendulum devices as an isolation system placed between piers top and deck. First, the outcomes of the seismic risk assessment of the existing bridge, performed using an incremental noniterative Nonlinear Static Procedure, based on the Capacity Spectrum Method as well as the Inelastic Demand Response Spectra, are described and discussed. Then, a specific multilevel design process, based on a proper application of the hierarchy of strength considerations and the Direct Displacement-Based Design approach, is adopted to dimension the FPD devices. Furthermore, to assess the impact of the FPD nonlinear behaviour on the bridge seismic response, a device model that reproduces the variation of the normal force and friction coefficient, the bidirectional coupling, and the large deformation effects during nonlinear dynamic analyses was used. Finally, the paper examines the effects of the FPD modelling parameters on the behaviour of the retrofitted bridge and assesses its seismic response with the results pointing out the efficiency of the adopted seismic retrofit solution