Analysis of model parameters affecting the pressure profile in a circulating fluidized bed

This study focuses on continuum model validation of the flow of air and small catalyst particles in a circulating fluidized bed. Comparison with available experimental data of pressure drop and solids circulation rate in the riser clearly demonstrates the need to modify the homogeneous drag model to accurately predict the formation of clusters of particles, which are typically observed in the fluidization of small particles. The need to correct the drag law is also demonstrated in simulations of polydisperse powder flows wherein three solids species are used to represent a typical catalyst size distribution. Finally, particle‐wall friction is found to have the most significant effect on the vertical gas pressure gradient while particle–particle friction has only a minor effect. Published 2011 American Institute of Chemical Engineers AIChE J, 58: 427–439, 2012     

Quantifying the uncertainty introduced by discretization and time‐averaging in two‐fluid model predictions

The two‐fluid model (TFM) has become a tool for the design and troubleshooting of industrial fluidized bed reactors. To use TFM for scale up with confidence, the uncertainty in its predictions must be quantified. Here, we study two sources of uncertainty: discretization and time‐averaging. First, we show that successive grid refinement may not yield grid‐independent transient quantities, including cross‐section–averaged quantities. Successive grid refinement would yield grid‐independent time‐averaged quantities on sufficiently fine grids. Then a Richardson extrapolation can be used to estimate the discretization error, and the grid convergence index gives an estimate of the uncertainty. Richardson extrapolation may not work for industrial‐scale simulations that use coarse grids. We present an alternative method for coarse grids and assess its ability to estimate the discretization error. Second, we assess two methods (autocorrelation and binning) and find that the autocorrelation method is more reliable for estimating the uncertainty introduced by time‐averaging TFM data. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5343–5360, 2017     

Experimental study of PLA thermal behavior during fused filament fabrication

Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts.     

Synthesis,characterization and electrochemical performance of Sn3F3PO4 anode material for lithium-ion batteries

Tin fluorophosphate (Sn₃F₃PO₄) powder was synthesized via a microemulsion route. Physical properties of the synthesized material were investigated by means of X-ray powder diffractometry (XRD) and field emission scanning electron microscopy (FE-SEM). The investigation showed that the synthesized powder was crystalline Sn₃F₃PO₄ with needle-like morphology with a thickness of 300–500 nm and length of 5–10 μm. The electrochemical performance of the synthesized powder as a negative electrode for Li-ion batteries was studied. The results showed that the synthesized Sm₃F₃PO₄ possessed an initial discharge capacity of 1370 mAh g^?1 and charge capacity of 968 mAh g^?1 in a potential range of 0.005–3 V. In addition, the material showed capacity retention of 70.8% after 30 cycles at a constant current density of 100 mA g^?1.     

Pansharpening multispectral remote sensing data by multiplicative joint nonnegative matrix factorization

Pansharpening aims at combining observable panchromatic and multispectral images to generate an unobservable image with the high spatial resolution of the former and the spectral diversity of the latter. In this paper a new fusion method is proposed. This method, related to linear spectral unmixing (LSU) techniques and based on non-negative matrix factorization (NMF), optimizes, by new iterative–multiplicative update rules, a joint criterion that exploits a spatial degradation model between the two images. The proposed Multiplicative Joint Non-negative Matrix Factorization (MJNMF) approach is applied to synthetic and real data, and its effectiveness in spatial and spectral domains is evaluated with commonly used performance criteria. Experimental results show that the proposed method yields good spectral and spatial fidelities of the pansharpened data. Also, it outperforms those tested from the literature.     

Harnessing knowledge workers' participation for IT planning effectiveness: the informational and motivational mediating effects of users' microplanning behaviour

In most organizations, knowledge is produced on a continuous basis such that formal planning methods fail to capture it on time for utilization into effective IT solutions. Microplanning, as user-led informal planning behaviour, allows users as knowledge workers to continuously use their knowledge and skills to identify opportunities for using IT or replanning its existing use. This is the informational effect of microplanning. Microplanning is also an empowering process which enhances users' own motivation. This empowerment effect is referred to as the motivational effect. User microplanning behaviour therefore constitutes the main construct of the model of microplanning effectiveness described in this study. It yields effectiveness through two paths, informational and motivational. After operational definitions for the variables were derived, the two main hypotheses of the study were empirically tested on a sample of 263 knowledge workers. Results of the study fully support the informational and motivational effects of microplanning.     

Trypsin from zebra blenny (Salaria basilisca) viscera: Purification,characterisation and potential application as a detergent additive

An alkaline trypsin was purified from the viscera of zebra blenny (Salaria basilisca) by ammonium sulphate (40?80% saturation) precipitation, Sephadex G-100, Mono Q-Sepharose and ultrafiltration. A yield of 12% with a purification-fold of 4.2 was obtained. The trypsin had an apparent molecular weight of 27 kDa. Soybean trypsin inhibitor and phenylmethylsulfonyl fluoride showed a strong inhibitory effect on the purified trypsin. Trypsin had maximal activity at pH 9.5 and 60 °C for the hydrolysis of Nα-benzoyl-dl-arginine-p-nitroanilide (BAPNA). It was stable at low temperatures and in the pH range of 7.0?12.0. The N-terminal amino acid sequence of the first 12 amino acids of the purified protease was IVGGRECTEPSQ. S. basilisca trypsin, which showed high homology with other fish trypsins, had a charged Arg residue at position 5, where Tyr is common in marine vertebrates and mammalian trypsins. The trypsin kinetic constants, K_m and k_cat for BAPNA, were 0.6 mM and 1.38 s^?1, respectively.     

Numerical simulation of the transient hydrogen trapping process using an analytical approximation of the McNabb and Foster equation

In order to simulate hydrogen charging and discharging cycles of mechanically loaded structures, an analytical solution for the differential equation of trapping kinetics is proposed, as a generalization of the Oriani's equilibrium relationship.This solution has been implemented in the Abaqus finite element software, and validated by comparison with the one-dimensional kinetic MRE Hydrogen Isotope Inventory Processes Code (HIIPC). Last, the results of an application on a 3D structure are presented.     

Methanol synthesis from CO2 and H2 in multi-tubular fixed-bed reactor and multi-tubular reactor filled with monoliths

This work investigates the impact of catalyst structuring into particles or monoliths on methanol production from only CO₂ and H₂ at a large scale. Methanol synthesis in multi-tubular reactors is evaluated using packed-bed and monolithic reactors by modeling heat and mass transfer in each reactor. The obtained simulation results show that, at low gas hourly space velocity (GHSV = 10,000 h⁻¹), the performances of both reactor technologies are similar. In this case, the packed-bed reactor technology is the most appropriate technology due to its simplicity of installation and operation. At high GHSV (25,000 h⁻¹), the packed-bed reactor technology is limited by a considerable pressure drop that causes an important loss in productivity due to thermodynamic equilibrium, whereas the monolithic reactors exhibit negligible pressure drop and achieve far better performances.     

Influence of process parameters on thermal and mechanical properties of polylactic acid fabricated by fused filament fabrication

Fused filament fabrication is considered one of the most used processes in additive manufacturing rapid prototypes out of polymeric material. Poor strength of the deposited layers is still one of the main critical problems in this process, which affects the mechanical properties of the final parts. To improve the mechanical strength, investigation into various process parameters must be considered. In this article, the influence of different process parameters has been experimentally investigated by means of physicochemical and mechanical characterizations. Special attention was given to the thermal aspect. In that respect, the in situ measurement of temperature profile during deposition indicated that several parameters affect the cooling rate of material and consequently have an influence on the final parts. It was found that the influence of increasing the extruder temperature is more significant in comparison with other process parameters.