MRI investigations of particle motion within a three-dimensional vibro-fluidized granular bed

The unique ability of magnetic resonance imaging (MRI) to provide spatial and temporal information from optically opaque systems, in three dimensions, make it an ideal tool to study the internal motion of rapid granular flows. This paper will focus on the use of ultra-fast velocity compensated MRI measurements to study particle velocity and density distributions in a granular gas, produced by vibrating vertically a bed of mustard seeds at 40 Hz. Specifically, a velocity compensated, double spin-echo, triggered, one-dimensional MRI profiling pulse sequence was developed. This gives an MRI temporal resolution of approximately 2 ms and also minimises MRI velocity artefacts. 12 phase measurements per vibration cycle were used. The data can be used to extract values of the mustard seed average velocity and velocity propagators (probability distributions functions) as a function of the phase of the vibration cycle and vertical height within the cell. The data show strong transient effects during the impact phase of the vibration. A detailed discussion of the temporal passage of the individual phase resolved, height resolved velocity distributions, along with seed velocity propagators at a fix height from the vibrating base is presented.     

Cross-section control of stacked nanowires formed by Bosch process and oxidation

The cross-sectional shape of the stacked silicon nanowires (SiNWs) formed by the Bosch process and stress-limited oxidation is studied in this paper. Under the condition of high temperature oxidation, the resulting nanowires highly resemble the initial shapes resulting by the Bosch process. The effects of etching and passivation in the Bosch process are modeled to provide a guideline to control the cross-section of the stacked nanowires.     

Uniformity enhancement of incident dose on concave surface in plasma immersion ion implantation assisted by beam-line ion source

Plasma immersion ion implantation (PIII) is a promising surface treatment technique for the irregular-shaped components. However, it is difficult to achieve uniform implantation along the surface of a concave sample due to the propagation and overlapping effect of plasma sheath. In this paper, a new ion implantation process is presented for improving the dose uniformity, especially for enhancing the lateral dose of the samples with concavities. In PIII enhanced by beam-line ions process, a beam-line ion source with certain energy is introduced from an external source into the concavity to suppress the sheath propagation and consequently to improve the dose uniformity. The time-dependent evolution of the potential, electrical field and the particle movement surrounding the surface of concave sample is studied by a particle-in-cell/Monte Carlo collision (PIC/MCC) simulation during a single bias high voltage (HV) pulse. The simulation results show that the plasma sheath propagation surrounding the concave sample is suppressed effectively by beam-line ions, and can be quasi-steady state during a single HV pulse. The influence of the energy of induced beam-line ions on the incident ion dose and energy distribution is discussed. Compared with the traditional PIII process, the dose uniformity of the sample surface is improved obviously due to the increase of the ions implanted into the lateral surface.     

Critical Factors Determining the Onset of Backdraft Using Solid Fuels

Fire Technology - Backdraft is an explosive fire phenomenon which typically occurs during fire-fighting activities, occasionally leading to fire-fighter fatalities. Real backdraft incidents involve...     

A sequencing approach for creating new train timetables

Train scheduling is a complex and time consuming task of vital importance. To schedule trains more accurately and efficiently than permitted by current techniques a novel hybrid job shop approach has been proposed and implemented. Unique characteristics of train scheduling are first incorporated into a disjunctive graph model of train operations. A constructive algorithm that utilises this model is then developed. The constructive algorithm is a general procedure that constructs a schedule using insertion, backtracking and dynamic route selection mechanisms. It provides a significant search capability and is valid for any objective criteria. Simulated Annealing and Local Search meta-heuristic improvement algorithms are also adapted and extended. An important feature of these approaches is a new compound perturbation operator that consists of many unitary moves that allows trains to be shifted feasibly and more easily within the solution. A numerical investigation and case study is provided and demonstrates that high quality solutions are obtainable on real sized applications.     

Effect of low frequency vibration on macro and micro structures of LM6 alloys

This study summarises research into the effect of low frequency mechanical vibration on the macro and microstructures of LM6 [Al-Si 12.30%] alloy. Vibration at varying frequencies between 15 and 41.7 Hz and amplitudes between 0.125 and 0.5 mm has been applied to both unmodified and metallic sodium modified LM6 alloys during solidification. The effect of low frequency vibration on the grain size, shrinkage pipe and eutectic silicon were analysed using quantitative metallography. The results indicated that(1) The pipe in the ingot was reduced by vibration with increasing frequency and amplitude.(2) Pipe elimination was more effective with increasing time of vibration of the liquid.(3) Vibration with increasing frequency and amplitude produced grain refinement.(4) Vibration caused coarsening in the eutectic silicon in unmodified and sodium modified LM6 alloy, the extent of which increased with increasing vibration time.(5) Primary silicon in LM6 alloys was coarsened by vibration.     

Kinetics of reversible addition–fragmentation transfer (RAFT) miniemulsion polymerization of styrene using dibenzyl trithiocarbonate as RAFT reagent and costabilizer

The roles of dibenzyl trithiocarbonate (DBTTC) as both costabilizer and reversible addition–fragmentation transfer (RAFT) reagent in RAFT miniemulsion polymerizations of styrene were investigated. The effectiveness of DBTTC costabilizer in retarding Ostwald ripening involved in the storage stability of miniemulsion is comparable to that of conventional low‐molecular‐weight costabilizers such as cetyl alcohol, but inferior to that of hexadecane. The major variables chosen for studying kinetics of RAFT miniemulsion polymerizations include the type of initiators and levels of DBTTC and surfactant. At a constant level of DBTTC, the rate of polymerization for benzoyl peroxide (BPO)‐initiated polymerization is slower than that for sodium persulfate (SPS)‐initiated polymerization. Furthermore, the polymerization rate decreases with increasing level of DBTTC for polymerizations initiated by BPO (or SPS). It is the monomer droplet nucleation that governs BPO‐initiated polymerizations. In contrast, for SPS‐initiated polymerizations, the probability for homogeneous nucleation to take place is greatly increased, especially for polymerizations with lower levels of DBTTC and higher levels of surfactant. © 2015 Society of Chemical Industry     

Cycle synthesis and optimization of a VSA process for postcombustion CO2 capture

A systematic analysis of several vacuum swing adsorption (VSA) cycles with Zeochem zeolite 13X as the adsorbent to capture CO₂ from dry, flue gas containing 15% CO₂ in N₂ is reported. Full optimization of the analyzed VSA cycles using genetic algorithm has been performed to obtain purity‐recovery and energy‐productivity Pareto fronts. These cycles are assessed for their ability to produce high‐purity CO₂ at high recovery. Configurations satisfying 90% purity‐recovery constraints are ranked according to their energy‐productivity Pareto fronts. It is shown that a 4‐step VSA cycle with light product pressurization gives the minimum energy penalty of 131 kWh/tonne CO₂ captured at a productivity of 0.57 mol CO₂/m³ adsorbent/s. The minimum energy consumption required to achieve 95 and 97% purities, both at 90% recoveries, are 154 and 186 kWh/tonne CO₂ captured, respectively. For the proposed cycle, it is shown that significant increase in productivity can be achieved with a marginal increase in energy consumption. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4735–4748, 2013     

Multimodal Transportation Flows in Energy Networks with an Application to Crude Oil Markets

Networks and Spatial Economics - Network models of energy markets have been beneficial for analyses and decision-making to tackle challenges related to the production, distribution and consumption...     

Managing the design and implementation of a Real-Time Computerized Monitoring system for a textile environment

The installation of computerized systems to aid data accumulation is critical in the correct application of incentive pay, production control/scheduling and other operations in a Textile environment. This paper presents a framework by which a project of this type can be taken from inception to completion. Application of the framework will be demonstrated by an analogy with just such a system currently being used in a textile weaving environment.