Cavity soliton molecules and all-optical push-broom effect

We present an improved model for cavity soliton generation by coupling frequency-selective feedback to a vertical cavity surface emitting laser with a saturable absorber. The frequency-selective feedback is found to lower down the threshold pump power for cavity soliton generation and eventually to broaden the stability regime. A new dynamics of cavity solitons is revealed in form of “all-optical push-broom effect.” Also, stable bound states of cavity solitons that resemble linear diatomic and polyatomic molecules are predicted with their stability regions marked. The findings can be exploited for experimental realization of a soliton force microscope and all-optical memory devices

Generation and dynamics of one-and two-dimensional cavity solitons in a vertical-cavity surface-emitting laser with a saturable absorber and frequency-selective feedback

Cavity solitons are predicted in a vertical-cavity surface-emitting laser with a saturable absorber and coupled to an external frequency-selective feedback element. An entirely variational-method-based analytical study of the complex Ginzburg–Landau equation—the governing equation of the system—gives rise to one- and two-dimensional cavity solitons. Both types of cavity solitons are verified stable by Lyapunov stability analysis. Stability regions are identified for both types and are found to shrink for higher dimensions. Split-step Fourier-method-based direct numerical analysis of the governing equation exhibits matching results for the existence and stability of the cavity solitons. Cavity soliton interaction has been studied numerically. All-optical control on cavity solitons has been demonstrated by introducing a phase gradient. Cavity solitons thus generated have potential applications in optical information technology

Numerical simulation of fluidized dense-phase pneumatic conveying of powders to develop improved model for solids friction factor

Accurate prediction of the solids friction factor through horizontal straight pipes is important for the reliable design of a pneumatic conveying system, but it is a challenging assignment to date because of the highly concentrated, turbulent, and complex nature of the gas–solids mixture. Power-station fly ash was transported through different pipeline configurations. Numerical simulation of the dense-phase pneumatic conveying systems for three different solids and two different air flow rates have shown that particle and actual gas velocities and the ratio of the two velocities increases in the flow direction, whereas the reverse trend was found to occur for the solids volumetric concentration. To develop a solids friction-factor model suitable for dense-phase flow, we modified an existing pure dilute-phase model by incorporating sub-models for particle and actual gas velocities and impact and solids friction factor. The solids friction-factor model was validated by using it for scale-up predictions for total pipeline pressure drops in longer and larger pipes and by comparing experimental and predicted pneumatic conveying characteristics for different solids flow rates. The accuracy of the prediction was compared with a recently developed two-layer-based model. We discussed the effect of incorporating the particle and actual gas velocity terms in the solids friction-factor model instead of superficial air velocity

Cross recurrence quantification analysis of gas-solid flow in pneumatic conveying of plastic pellets using electrostatic sensors

Gas-solid flow synchronisation behaviour of plastic pellets were characterised, and particle velocities were processed using cross-recurrence quantification analysis (CRQA) of electrostatic sensors at different pneumatic conveying operating conditions, including air velocity and solids mass flow rates. Time-series data were collected from arc-shaped electrostatic sensors to reconstruct phase spaces (attractors) using the time delay coordinate embedding method. Cross-recurrence plots were developed from the reconstructed phase spaces to visualise the shared topology in two arc-shaped electrostatic sensors at two locations in a horizontal pipeline. CRQA measures, such as recurrence rate and determinism, were applied to the cross-recurrence plots to quantify the synchronisation between the two sensors for different gas-solid flow patterns: stratified flow, pulsating flow, moving dunes and blowing dunes. The flow patterns were identified using high-speed video imaging sight section of a pipeline and classified at several operating conditions in a flow pattern map and state diagram. The optimal operating conditions at the minimum conveying air velocity in the state diagram are between moving and blowing dunes. The CRQA measures and particle velocity were correlated with the state diagram to understand their relationship at optimal conditions. It was found that the CRQA measures can be used to detect changes in solids mass flow rate and air velocity

On developing improved modelling and scale-up procedures for pneumatic conveying of fine powders

Pneumatic transport of fine powders in fluidized dense-phase mode is becoming increasingly popular in various industries, such as power, chemical, cement, refinery, alumina, pharmaceutical, limestone, to list a few, because of the reasons of reduced gas flow rate and power consumption, decreased conveying velocities, improved product quality control, reduced pipeline sizing and wear rate, increased workplace safety etc. For the reliable design of a pneumatic conveying system, it is important to accurately predict the total pipeline pressure drop. However, accurate prediction of pressure drop from an improved understanding of the fundamental transport mechanism of fluidized dense-phase flow condition has only made limited progress till now because of the highly concentrated and turbulent nature of the gas-solids mixture. Power plant fly ash (median particle diameter: 30 μm; particle density: 2300 kg/m3; loose-poured bulk density: 700 kg/m3) was conveyed through different pipelines (69 mm I.D. × 168 m long; 105 mm I.D. × 168 m long; 69 mm I.D. × 554 m long). 8 different fly ash samples were tested in a fluidizing column for their deaeration characteristics and fluidized bulk densities were determined. Governing equations of flow for the dense-phase pneumatic conveying system of fine powders were solved using RungeKutta-Fehlberg (RKF45) method for different fluidized bulk densities of fly ash and air flow rates. The results have shown that the particle and actual gas velocities and the ratio of the two velocities increase in the direction of flow, while a reverse trend was apparent for the solids volumetric concentration. The results were compared against the predictions obtained using existing empirical relations for particle velocity. To develop an improved model for solids friction factor, an existing reliable pure dilute-phase model has been modified for dense-phase flow condition by incorporating sub-models for particle to actual gas velocity and impact and solids friction factor. The developed solids friction factor model was validated by using it to predict the total pipeline pressure drops for larger and longer pipelines and by comparing the experimental and predicted pneumatic conveying characteristics. The results have shown improved reliable predictions and that the model is capable of addressing the gradual transition of flow mechanism from dense- to dilute-phase. The accuracy of prediction is similar (in fact better in certain scale-up cases) when compared to a recently developed two-layer based model (developed by some of the authors). The results demonstrate the importance of incorporating particle and actual gas velocity terms in the model of solids friction factor instead of the prevailing techniques that overly depend on using superficial gas velocities

Application of nonlinear dynamics analysis to gas-solid flow system in horizontal pneumatic conveying of plastic pellets

Chaotic invariant and recurrence quantification analysis measures have characterised fully developed gas-solid flow in horizontal pneumatic conveying of plastic pellets. These measures describe the complexity in phase spaces (attractors) and recurrence plots, reconstructed from pressure and bottom arc-shaped electrostatic signals to characterise the behaviour of flow patterns. Different flow patterns were identified using high-speed video imaging of a transparent pipeline and classified at several operating conditions in a flow pattern map and state diagram. Recurrence plots were analysed for the identified flow patterns, which showed different qualitative structures. The chaotic invariant and recurrence quantification analysis measures were correlated with the state diagram, indicating that the fluctuations of pressure senor and electrostatic sensor signals can classify the flow patterns at different operating conditions. Combining the analysis measures for electrostatic signals can indicate whether the flow condition is above, near or below the minimum energy consumption operating conditions

Experimental and numerical study on gas-solid flow system of plastic pellets using recurrence quantification analysis of pressure sensor measurements

The recurring dynamics of fully developed gas-solid flow patterns are characterised using recurrence quantification analysis measure in horizontal pneumatic conveying of plastic pellets. This measure was applied to recurrence plots, developed from phase spaces (attractors) reconstructed from pressure signals to characterise the recurring dynamics of flow patterns: stratified flow, pulsating flow, moving dunes and blowing dunes. The recurrence plot is a representation of the recurring dynamics in the attractor. Recurrence plots were analysed for flow patterns which showed different qualitative structures. The qualitative structures of recurrence plots at different operating parameters are measured using recurrence quantification analysis such as recurrence rate (RR). The RR measure was correlated with the state diagram, indicating that the recurring dynamics of pressure signals can detect the change between moving dunes and blowing dunes at a specific range of operating conditions

An integrated general practice and pharmacy-based intervention to promote the use of appropriate preventive medications among individuals at high cardiovascular disease risk: protocol for a cluster randomized controlled trial

Background: Cardiovascular diseases (CVD) are responsible for significant morbidity, premature mortality, and economic burden. Despite established evidence that supports the use of preventive medications among patients at high CVD risk, treatment gaps remain. Building on prior evidence and a theoretical framework, a complex intervention has been designed to address these gaps among high-risk, under-treated patients in the Australian primary care setting. This intervention comprises a general practice quality improvement tool incorporating clinical decision support and audit/feedback capabilities; availability of a range of CVD polypills (fixed-dose combinations of two blood pressure lowering agents, a statin ± aspirin) for prescription when appropriate; and access to a pharmacy-based program to support long-term medication adherence and lifestyle modification. Methods: Following a systematic development process, the intervention will be evaluated in a pragmatic cluster randomized controlled trial including 70 general practices for a median period of 18 months. The 35 general practices in the intervention group will work with a nominated partner pharmacy, whereas those in the control group will provide usual care without access to the intervention tools. The primary outcome is the proportion of patients at high CVD risk who were inadequately treated at baseline who achieve target blood pressure (BP) and low-density lipoprotein cholesterol (LDL-C) levels at the study end. The outcomes will be analyzed using data from electronic medical records, utilizing a validated extraction tool. Detailed process and economic evaluations will also be performed. Discussion: The study intends to establish evidence about an intervention that combines technological innovation with team collaboration between patients, pharmacists, and general practitioners (GPs) for CVD prevention. Trial registration: Australian New Zealand Clinical Trials Registry ACTRN1261600023342

A generic travelling wave solution in dissipative laser cavity

A large family of cosh-Gaussian travelling wave solution of a complex Ginzburg–Landau equation (CGLE), that describes dissipative semiconductor laser cavity is derived. Using perturbation method, the stability region is identified. Bifurcation analysis is done by smoothly varying the cavity loss coefficient to provide insight of the system dynamics. He’s variational method is adopted to obtain the standard sech-type and the notso-explored but promising cosh-Gaussian type, travelling wave solutions. For a given set of system parameters, only one sech solution is obtained, whereas several distinct solution points are derived for cosh-Gaussian case. These solutions yield a wide variety of travelling wave profiles, namely Gaussian, near-sech, flat-top and a cosh-Gaussianwith variable central dip. A split-step Fourier method and pseudospectral method have been used for direct numerical solution of the CGLE and travelling wave profiles identical to the analytical profiles have been obtained. We also identified the parametric zone that promises an extremely large family of cosh-Gaussian travelling wave solutions with tunable shape. This suggests that the cosh-Gaussian profile is quite generic and would be helpful for further theoretical as well as experimental investigation on pattern formation, pulse dynamics andlocalization in semiconductor laser cavity