The transition from conservative to dissipative flows in class-B laser model with fold-Hopf bifurcation and coexisting attractors

Dynamical behaviors of a class-B laser system with dissipative strength are analyzed for a model in which the polarization is adiabatically eliminated. The results show that the injected signal has an important effect on the dynamical behaviors of the system. When the injected signal is zero, the dissipative term of the class-B laser system is balanced with external interference, and the quasi-periodic flows with conservative phase volume appear. And when the injected signal is not zero, the stable state in the system is broken, and the attractors (period, quasi-period, and chaos) with contractive phase volume are generated. The numerical simulation finds that the system has not only one attractor, but also coexisting phenomena (period and period, period and quasi-period) in special cases. When the injected signal passes the critical value, the class-B laser system has a fold-Hopf bifurcation and exists torus ”blow-up” phenomenon, which will be proved by theoretical analysis and numerical simulation.

Influence of Groove Structure Parameters Based on Optimal Mass Transfer Coefficient on Vaporization Characteristics and Sealing Performance of Liquid Film Mechanical Seals

In this study, a spiral groove liquid film vaporization model based on the viscosity–temperature equation, fluid internal friction, saturation temperature, and pressure relationship equation was established. Using a multiphase flow model based on the finite volume method, the influence of the change in the mass transfer coefficient on the vaporization of the liquid film was studied. Moreover, the influence law of structural parameter changes in liquid film vaporization characteristics and sealing performance was analyzed. The results indicate that, with an increase in the mass transfer coefficient, the average vapor phase volume fraction first increases and then gradually stabilizes. When calculating the average vapor phase volume fraction, it is necessary to consider the influence of the mass transfer coefficient, whereas its effect on the opening force and leakage can usually be neglected. Under the optimal mass transfer coefficient conditions, the average vapor phase volume fraction increases with an increase in the helix angle, groove-weir ratio, and groove depth. By comparison, with an increase in the groove-diameter ratio, the average vapor phase volume fraction first increases and then decreases. The opening force decreases with an increase in the helix angle, groove-to-weir ratio, and groove depth. On the other hand, it first decreases and then increases with an increase in the groove-diameter ratio. The leakage rate increases first and then stabilizes with an increase in the helix angle. Moreover, it increases continuously with an increase in the groove-diameter ratio, groove-weir ratio, and groove depth.

Formulation and Development of Aceclofenac loaded Microsponges Topical Drug Delivery System using quality by Design Approach

The proposed study is focussed at developing Aceclofenacmicrosponges for topic drug delivery systems. QbD was applied for better understanding of the process and to generate design space, using quality target product profile, critical quality attributes, and risk assessment. The aim of the experiment was to prepare a safe, efficacious, stable and patient compliant microsponge dosage form of Aceclofenac. Materials and methods: Pre-formulation studies were carried out which helped in developing an accurate dosage form. UV, FTIR, DSC, and SEM studies were done for pre-formulation and post-formulation evaluations. These study deals with the design and optimization of Aceclofenacmicrosponges loaded topical drug delivery system to the controlled release of active drug into the skin in order to minimize the systemic exposure and minimize local cutaneous reactions to active drugs by DoE method of QbD Approach. AceclofenacMicrosponges were prepared by quasi emulsion solvent diffusion method using Eudragit-RS100 as a polymer, polyvinyl alcohol, Ethanol as Internal phase volume and Liquid paraffin as External phase volume. In this study, we found that the controlled release of aceclofenac microsponges.

A New Definition of the Stationary Phase Volume in Mixed-Mode Chromatographic Columns in Hydrophilic Liquid Chromatography

Polar columns used in the HILIC (Hydrophilic Interaction Liquid Chromatography) systems take up water from the mixed aqueous–organic mobile phases in excess of the water concentration in the bulk mobile phase. The adsorbed water forms a diffuse layer, which becomes a part of the HILIC stationary phase and plays dominant role in the retention of polar compounds. It is difficult to fix the exact boundary between the diffuse stationary and the bulk mobile phase, hence determining the column hold-up volume is subject to errors. Adopting a convention that presumes that the volume of the adsorbed water can be understood as the column stationary phase volume enables unambiguous determination of the volumes of the stationary and of the mobile phases in the column, which is necessary for obtaining thermodynamically correct chromatographic data in HILIC systems. The volume of the aqueous stationary phase, Vex, can be determined experimentally by frontal analysis combined with Karl Fischer titration method, yielding isotherms of water adsorbed on polar columns, which allow direct prediction of the effects of the composition of aqueous–organic mobile phase on the retention in HILIC systems, and more accurate determination of phase volumes in columns and consistent retention data for any mobile phase composition. The n phase volume ratios of 18 columns calculated according to the new phase convention strongly depend on the type of the polar column. Zwitterionic and TSK gel amide and amine columns show especially strong water adsorption.

Microstructure Alteration in the High-Speed Machining of Titanium Alloy Involved With Tool Wear and Cryogenic Condition

The microstructure alteration generated in the high-speed machining of titanium alloy has significant influence on the performance, quality and service life of production. The prediction of grain size or phase distribution based on physics mechanism or the regression of experimental data have been reported in the process of static or quasi-static state. However, it is still a challenge to predict the phase transformation and grain growth process in machining accurately and effectively since it has characteristics of high strain, strain rate and temperature. In this paper, a novel FEM-based model involving with the microstructure alteration was introduced and implemented to predict finial grain size or phase result in the high-speed machining of Ti-6Al-4V alloys especially at the machined surface. The phase transformation process was proposed and discussed by considering tool wear and cryogenic condition at machined surface, while the microstructure results were displayed on the chip in the previous works. Firstly, the phase volume fraction and grain size were modelled by experimental data. Then the simulation based on the self-consistent method (SCM) was used to output strain and temperature distribution. Thirdly, the phase volume fraction and grain size expressions were transmitted into subroutine programs and the microstructure alteration process under the different cutting conditions were showed in the FE results. The simulation results of temperature, phase fraction and strain were compared against previous simulation or experiment results in published papers revealing good agreement. The proposed model was further to investigate the influence of tool wear and cutting temperature on machined surface. The results indicated that the tool wear increased heat at the flank face significantly resulting to β phase increasing and grain growth at machined surface and the cryogenic condition would lower temperature gradient as well as stress gradient contributing to reduce roughness and residual stress.

On the method for the analysis of compulsive phase mixing and its application in cosmogony

In this paper, we study the strong non-stationary stochastic processes that take place in the phase space of self-gravitating systems at the earlier non-stationary stage of their evolution. The numerical calculations of the compulsive phase mixing process were carried out according to the model of chaotic impacts, where the initially selected phase volume experiences random pushes that are of a diverse and complex nature. The application of the method for studying random impacts on a volume element in the case of three-dimensional space is carried out.

Directional Solidification of AlSi7Fe1 Alloy Under Forced Flow Conditions: Effect of Intermetallic Phase Precipitation and Dendrite Coarsening

A forced flow was experimentally shown to influence the solidification microstructure of metal alloys by modifying the coarsening/ripening law. In some technical alloys (AlSi7Fe1), this flow effect can also be significantly suppressed due to the formation of intermetallic precipitates (β-Al5FeSi) that can block the flow in the mushy region. The forced flow was induced by a rotating magnetic field (RMF). Herein, a three-phase volume-average-based solidification model is introduced to reproduce the above experiment. The three phases are the melt, the primary solid phase of columnar dendrites, and the second solid phase of intermetallic precipitates. The dynamic precipitation of the intermetallic phase is modelled, and its blocking effect on the flow is considered by a modified permeability. Dendrite coarsening, which influences the permeability, is also considered. The RMF induces a strong azimuthal flow and a relatively weak meridional flow (Ekman effect) at the front of the mushy zone during unidirectional solidification. This forced flow reduces the mushy zone thickness, induces the central segregation channel, affects the distribution of the intermetallic precipitates, and influences dendrite coarsening, which in turn modifies the interdendritic flow. Both interdendritic flow and the microstructure formation are strongly coupled. The modelling results support the explanation of Steinbach and Ratke—the formed intermetallic precipitates (β-Al5FeSi) can block the interdendritic flow, and hence influence the coarsening law. The distribution of β-Al5FeSi is dominantly influenced by the flow-induced macrosegregation. The simulation results of the Si and Fe distribution across the sample section are compared with the experimental results, showing good simulation–experiment agreement. Graphic Abstract During alloy solidifications the flow can influence the mushy zone by inducing macrosegregation, modifying the solidification microstructure, and influencing the formation of intermetallic precipitates. The resulting microstructural features can in turn affect the melt flow by changing the flow intensity and flow pattern. A three-phase volume-average-based solidification model is introduced to study the flow-solidification interaction, and hence to improve the knowledge on the formation mechanism of intermetallics and their effect on solidification. (a) Schematic for the flow pattern and formation of different phases; (b) experiment–simulation comparison of macrosegregation (Fe) across the diameter of as-solidified sample.

Effect of Gas Volume Fraction on the Gas-Phase Distribution in the Passage and Blade Surface of the Axial Flow Screw-Type Oil-Gas Multiphase Pump

The axial flow screw-type oil-gas multiphase pump is mainly applied to oil and gas transport in the deep sea. In the process of transporting the multiphase medium, the gas volume fraction (GVF) on the gas phase changes from time-to-time, resulting in the performance of the oil-gas multiphase pump being greatly influenced by the gas phase. This paper presents a detailed analysis of the gas-phase distribution law and the vortex distribution in the flow passages within the oil-gas multiphase pump by means of numerical calculations, supplemented by experimental verification. The results show that the gas phase is mainly concentrated in the diffuser at different GVFs, and the gas phase gathering in the diffuser becomes more significant with the increase in the GVF. The gas-phase volume fraction increases gradually from rim to hub, that is, the gas-phase gathering degree increases. The maximum gas-phase volume distribution area is mainly concentrated in the area near the hub of the diffuser inlet and the middle blade height area at the outlet of the diffuser. The flow in the impeller is relatively stable under the different GVFs, while there is a large vortex near the inlet of the diffuser near the hub, and there is a backflow phenomenon between the outlet of the diffuser and the tip clearance of the impeller. The volume fraction of the gas phase near the rim fluctuates more than that near the hub because the gas phase is squeezed by the liquid phase more violently. The research results can provide theoretical guidance for the optimal design of oil-gas multiphase pump blades.