On the identification of rheological properties of cement suspensions: Rheometry,Computational Fluid Dynamics modeling and field test measurements

Cementitious composites with customized rheologies are becoming increasingly popular throughout a wide variety of civil engineering applications. Assessing their fundamental rheological properties is crucial for the success of a particular application. Their measurement is not a trivial task and typically requires dedicated and expensive equipment. These equipment may not be compatible with field applications and not even available in every laboratory. Correlations between fundamental rheological properties and field test measurements have been assessed, as for the yield stress versus the slump flow diameter. As for the plastic viscosity, different attempts have been made, with flow time parameters measured from different tests. This work provides further evidence to the aforementioned correlations, with reference to a broad range of cement pastes and mortars formulated from SCCs, as well as employing a tool for Computational Fluid Dynamics (CFD) modeling developed by the authors.     

Fabrication of metallic Cd multifarious prismatic microcrystals (CMPMCs) under NH3 gas ambient

We report here highly dense and pure metallic cadmium (Cd) multifarious prismatic microcrystals (CMPMCs) fabricated by thermal decomposition of cadmium oxide (CdO) powder at 700 °C for 60 min under NH₃ gas ambient inside horizontal tube furnace. CMPMCs were observed to be 1-1.5 μm in size with interesting morphologies of various cross sections such as triangular, trapezoidal, pentagonal and hexagonal etc. having solid, hollow/semi-hollow appearances. The as-synthesized CMPMCS were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Room temperature photoluminescence (PL) spectrum for Cd metal microcrystals exhibited a prominent emission band at 365 along with a shoulder peak at 404 nm. The UV main emission band is ascribed to radiative recombination of the electrons in the s, p conduction band near the Fermi surface and holes in the d bands generated under xenon light excitation whereas shoulder peak may be owing to surface oxidation effects or induced defects. This study shows the potential of CMPMCs for applications in optical devices. Based on vapour-solid (VS) process, growth mechanism for the formation of CMPMCs is also proposed and discussed briefly.     

Power profiling of multimedia sensor node with name-based segment streaming

Multimedia Tools and Applications - Multimedia streaming from miniaturized sensors is attractive for a wide range of web-based applications, including surveillance and Internet of Things (IoT)...     

Tunable structural and electrical impedance properties of ordered and disordered iron oxide phases for capacitive applications

Having extensive knowledge of room temperature and temperature dependent dielectric and impedance properties of iron oxide nanostructures will help in extending the field of application from biomedical sciences to microelectronics industry. This aspect of iron oxide has long been neglected and the attention is mostly focused on magnetic investigations. To explore and extend the field of application of iron oxide this study is focused on detailed investigation of structural as well as temperature dependent (30–210?°C) dielectric along with impedance analysis. Iron oxide nanostructures are prepared using template free oleic acid assisted sol-gel method with variation in molarity of the finally synthesized sol in the range of 0.2–2.0?mM (interval 0.2?mM). Magnetite (Fe₃O₄) phase is observed at molarity of 0.2?mM whereas, vacancy ordered and disordered maghemite (γ-Fe₂O₃) phases are observed at molarities of 0.8–1.0?mM and 1.4–2.0?mM, respectively. Dielectric constant of 104.6, 74.5 and 98.43 (log f = 5.0) is observed at molarities of 0.2?mM, 1.0?mM and 2.0?mM for Fe₃O₄ and vacancy ordered (V_o) & disordered (V_d) γ-Fe₂O₃ phase, respectively. Zview software is used for the fitting of Nyquist plots. Fitted data reveals that dielectric constant strongly depends on grain boundary resistance (R_gb). Activation energy of 0.25?eV and 0.296?eV (log f = 5) is observed for Fe₃O₄ and V_d γ-Fe₂O₃ phase at 0.2?mM and 2.0?mM molarity of the final iron oxide sol.     

Exact bit-error probability for optimum combining with a Rayleighfading Gaussian cochannel interferer

We derive expressions for the exact bit-error probability (BEP) for the detection of coherent binary phase-shift keying signals of the optimum combiner employing space diversity when both the desired signal and a Gaussian cochannel interferer are subject to flat Rayleigh fading. Two different methods are employed to reach two different, but numerically identical, expressions. With the direct method, the conditional BEP is averaged over the fading of both signal and interference, With the moment generating function based method, expressions are derived from an alternative representation of the Gaussian Q-function     

Electrostatic charging during the flow of grains from a cylinder

Electrostatic charging is ubiquitous in granular processing, leading to problems of safety, jamming and unwanted material segregation. To better understand the mechanics of granular charging, we focus here on flow through a metal cylinder, where we can isolate charging regions near the cylinder walls from noncharging regions further away. We confirm that monodisperse grains charge in proportion to the area of contact between grains and the cylinder walls, and so in large cylinders, most particles remain almost uncharged. Those particles that do charge reach a plateau charge density after filling the cylinder and flowing past the walls a distance of less than one and a half centimeters. For bidisperse granular blends, the net charge produced by the mixture is dominated by the component that comes into contact with the walls of the apparatus. This is found to be caused by segregation effects as well as the coating of the larger particles by the smaller ones. We make use of these results to predict the charge generated in mass flow hoppers, and we test these predictions. Finally we examine the effect of grounding the experimental apparatus, and we find that paradoxically, grounding does not prevent charge accumulation.     

Room temperature operation of GaAsSb/GaAs quantum well VCSELs at1.29 μm

Room temperature pulsed lasing at 1.29 μm in an optically pumped GaAsSb/GaAs quantum well VCSEL on a GaAs substrate is reported. This is the longest wavelength VCSEL reported in this material system     

Multi-Layer Hierarchical Rule Learning in Reactive Robot Control Using Incremental Decision Trees

This paper presents a new approach to the intelligent navigation of a mobile robot. The hybrid control architecture described combines properties of purely reactive and behaviour-based systems, providing the ability both to learn automatically behaviours from inception, and to capture these in a distributed hierarchy of decision tree networks. The robot is first trained in the simplest world which has no obstacles, and is then trained in successively more complex worlds, using the knowledge acquired in the previous worlds. Each world representing the perceptual space is thus directly mapped on a unique rule layer which represents in turn the robot action space encoded in a distinct decision tree. A major advantage of the current implementation, compared with the previous work, is that the generated rules are easily understood by human users. The paper demonstrates that the proposed behavioural decomposition approach provides efficient management of complex knowledge, and that the learning mechanism is able to cope with noise and uncertainty in sensory data.     

Numerical Model of Turbidity Currents with a Deforming Bottom Boundary

A numerical model of turbidity currents with a deforming bottom boundary has been developed. The model predicts the vertical structure of the flow velocity and concentration as well as change in the bed level due to erosion and deposition of suspended sediment. The Reynolds-averaged Navier–Stokes equations for dilute suspension have been solved using a finite volume method. The bottom boundary and the grid system are allowed to adjust in response to sediment deposition and entrainment during the computation. The model has been applied to simulate the evolution of a conservative saline density current and turbidity currents along an 11.6?m long flume that includes a slope followed by a horizontal bed. The model successfully simulates the evolution of the currents. Model results have been compared with the experimental data. Good similarity profiles of velocity and excess density or suspended sediment concentration are obtained at both the upstream supercritical and the downstream subcritical flow regions. A turbulent Schmidt number larger than one has been found to be appropriate for providing a good match with the experimental data. Changes in bed level predicted by the model have also been found to be in agreement with the experiment data.