CoopStor: a cooperative reliable and efficient data collection protocol in fault and delay tolerant wireless networks

Wireless Networks - Internet of things consist in the deployment of constrained and battery-powered devices with a radio interface. Most industrial applications require to respect strict...     

Ultra-high performance concrete and fiber reinforced concrete: achieving strength and ductility without heat curing

Ultra-high performance concrete (UHPC) and ultra-high performance fiber reinforced concrete (UHP-FRC) were introduced in the mid 1990s. Special treatment, such as heat curing, pressure and/or extensive vibration, is often required in order to achieve compressive strengths in excess of 150 MPa (22 ksi). This study focuses on the development of UHP-FRCs without any special treatment and utilizing materials that are commercially available on the US market. Enhanced performance was accomplished by optimizing the packing density of the cementitious matrix, using very high strength steel fibers, tailoring the geometry of the fibers and optimizing the matrix-fiber interface properties. It is shown that addition of 1.5% deformed fibers by volume results in a direct tensile strength of 13 MPa, which is 60% higher than comparable UHP-FRC with smooth steel fibers, and a tensile strain at peak stress of 0.6%, which is about three times that for UHP-FRC with smooth fibers. Compressive strength up to 292 MPa (42 ksi), tensile strength up to 37 MPa (5.4 ksi) and strain at peak stress up to 1.1% were also attained 28 days after casting by using up to 8% volume fraction of high strength steel fibers and infiltrating them with the UHPC matrix.     

Jet Mixing in Direct-Chill Casting of Aluminum: Crater Effects and its Consequence on Centerline Segregation

Recent reports have demonstrated the possibility of mitigating macrosegregation during the Direct-Chill casting of rolling slab ingots using an impinging jet. Herein, an analytical model is presented to predict the shape of the crater formed due to the impact of the jet on the slurry region. The model takes into account alloy composition, physical dimension, and casting speed on the distribution of forces and crater shape. The calculated shape of the crater profile is used to explain the centerline depletion in the impingement region previously reported.     

Life Gallery: event detection in a personal media collection

Multimedia Tools and Applications - Usage of camera-equipped mobile devices raises the need for automatically organizing large personal media collections. Event detection algorithms have been...     

Spatial distribution of dry matter in yellow fleshed cassava roots and its influence on carotenoid retention upon boiling

Understanding retention of carotenoids after different processing methods is important. This study was conducted to quantify dry matter content and carotenoids found in different sections of the cassava roots from six clones and to assess true retention of carotenoids after 30 min of boiling. Retention was quantified in normalized prisms taken from proximal, central and distal sectors of the root. Dry matter content (DMC) was measured along and across the roots and varied from 14.1 to 51.0%. DMC tended to be lower at the center of the root and in distal sections. DMC affected the homogeneity of the food matrix and, therefore, contributed in spatial variation in retention of carotenoids. Average true retention (dry matter basis) was 86.6% and ranged from 76.0 and 96.7% (averages per clone and section of the root, respectively). Retention was positively associated with carotenoid content in unprocessed samples, although the relationship was weak. The study shows that during boiling weight of samples changed from slight losses to gains of up to 40% (depending on original DMC of the uncooked root), resulting in an “apparent dilution” of the carotenoids. Results suggested the occurrence of some isomerization. All-trans β-carotene losses (13%) were partially explained by increases in the 13-cis (34%) and 15-cis (8%) isoforms, as well as lixiviation (< 1%) into the boiling water.     

Local strain measurements of yarns inside of 3D warp interlock fabric during forming process

The final geometry of 3D warp interlock fabric needs to be check during the 3D forming step to ensure the right locations of warp and weft yarns inside the final structure. Thus, a new monitoring approach has been proposed based on sensor yarns located in the fabric thickness. To ensure the accuracy of measurements, the observation of the surface deformation of the 3D warp interlock fabric has been joined to the sensor yarns measurements. At the end, it has been revealed a good correlation between strain measurement done globally by camera and locally performed by sensor yarns. Additionally, sensor yarns located in the two directions of the 3D warp interlock fabric have revealed a different forming behaviour depending on the architecture and the different slope values of the punch.     

Interfacial bonding of Flax fibre/Poly(l-lactide) bio-composites

The use of glass fibre reinforced polyester composites raises many health and safety and environmental questions. One alternative is the development of high performance bio-based bio-composites with low environmental impact. Improved understanding of interfacial properties is essential to optimise the mechanical properties and durability of these materials, but so far few data are available. The present work describes the interfacial characterization of Flax fibre/Poly(lactic) acid (PLLA) system at the micro-scale using the microbond test. Different thermal treatments have been carried out (cooling rate and annealing) in order to evaluate the influence of matrix and interfacial morphologies as well as residual stress on interfacial properties. Micromechanical models have been used to determine the interfacial shear strength. When cooling rate is slow, improved interfacial properties are observed.     

Post-yield response of cold-cambered wide flange steel beams

The post-yield response of steel beams is important in steel fabrication particularly for setting cambers. A commonly used cambering process known as “cold cambering” consists of bending the girder about its strong axis using single or dual symmetrically applied concentrated loads. This paper recasts available solutions for wide flange steel beams relating loads to permanent deformation in parametric form to determine the effect of cross-sectional geometry and load position on its post-yield response. Sensitivity analyses were then conducted to identify appropriate values of these key parameters and their impact on alternative cambering set-ups. This allows optimization of the cold cambering operation for single- and dual-load systems. The analysis shows that dual-load systems offer significant benefits over single-load systems as they develop the required camber profile at smaller loads without overstraining the steel section. The best results are obtained if the spacing between the two loads is kept within one-third to one-quarter of the span.