Double-phase Model Research Articles

Analytical and numerical examinations on the stability investigation of Casson nanofluid flow in a permeable layer controlled by vertical throughflow

Purpose The purpose of the study is to analytically as well as numerically investigate the weight of throughflow on the onset of Casson nanofluid layer in a permeable matrix. This study examines both the marginal and over stable kind of convective movement in the system. Design/methodology/approach A double-phase model is used for Casson nanofluid, which integrates the impacts of thermophoresis and Brownian wave, whereas for flow in the porous matrix the altered Darcy model is occupied under the statement that nanoparticle flux is disappear on the boundaries. The resultant eigenvalue problem is resolved analytically as well as numerically with the help of Galerkin process with the Casson nanofluid Rayleigh–Darcy number as the eigenvalue. Findings The findings revealed that the throughflow factor postpones the arrival of convective flow and reduces the extent of convective cells, whereas the Casson factor, the Casson nanoparticle Rayleigh–Darcy number and the reformed diffusivity ratio promote convective motion and also decrease the extent of convective cells. Originality/value Controlling the convective movement in heat transfer systems that generate high heat flux is a real mechanical challenge. The proposed framework proved that the use of throughflow is one of the most important ways to control the convective movement in Casson nanofluid. To the best of the authors’ knowledge, no inspection has been established in the literature that studies the outcome of throughflow on the Casson nanofluid convective flow in a porous medium layer. However, the convective flow of Casson nanofluid finds many applications in improving heat transmission and energy efficiency in a range of thermal systems, such as the cooling of heat-generating elements in electronic devices, heat exchangers, pharmaceutical practices and hybrid-powered engines, where throughflow can play a significant role in controlling the convective motion.

An estimation of the correctness of XRD results obtained from the analysis of materials with bimodal crystallite size distribution

36 powder artificial mixtures and 2 usual samples with a bimodal crystallite size distribution have been prepared and examined by an X-ray diffraction method. We estimated the capability of the Rietveld refinement at a “double-phase model” mode and the correctness of the results. The homogeneity and the crystallite sizes of pure phases used in the preparation of the mixtures were checked by TEM. In most cases, Rietveld refinement at a “double-phase model” mode provided reliable information about both the crystallite size and percentage of constituents. Reliability of XRD results was higher for the powder mixtures with a larger difference in crystallite sizes. It was found that the shape of the crystallites can have a significant impact on the analysis results, and for columnar crystals, the employed method did not always provide correct results. When size distribution of the material deviates from a bimodal one, the correctness of the result decreases. Such an investigation was performed for the first time.

Modeling and Maximizing Customer Equity

One of the most efficient criteria for achieving an optimal balance of resources among customer acquisition, retention and expansion efforts is the maximum customer equity. In this article the author proposes a new solution for the customer equity maximization problem. The proposed solution takes into account two elements not considered in the majority of customer equity models in the literature: the customer expansion concept and acquisition, retention and expansion floor rates. The article presents a double-phase model that employs a variation of the Lagrange multiplier method to solve this balancing challenge. Its main contribution consists in providing a more comprehensive framework for optimizing the balance among customer acquisition, retention and expansion investments. The new approach contributes also for improving customer relationship management (CRM) decisions. Additionally, it represents appropriately the complexity of relationships among the customer equity core variables.

Lithium intercalation with phase transitions in model systems of electrode materials for lithium power sources

A comparison was made for Li+ chemical diffusion coefficients (DLi) in graphite as calculated by mathematical models of Li+ intercalation under constant potential into semirestricted and restricted kinetic systems with mobile phase boundary and into a single-phase system. Close DLi values were calculated by means of double-phase models. The double-phase model produces 6–7-fold DLi coefficient as compared to the values of the single-phase model.

The Dipping Source X1254-690 Observed with GINGA

The results of Ginga observations of the dipping X-ray source X1254-690 are presented. The persistent emission spectrum cannot be represented with conventional two-component models; an additional spectral structure, which can be represented either by a broad emission line or by reflection by warm matter, is required. The energy spectra during dips can be represented by the sum of a non-absorbed component, which has the same spectral shape as the persistent emissions just before or after the dip, and an absorbed component, which is described by the persistent spectrum with additional absorption. The intensity of the non-absorbed component first decreases with decreasing intensity; then, the decrease saturates at about 8% of the persistent intensity. This strongly supports the existence of an accretion-disk corona of an electron-scattering optical depth of about 0.1. The column density of the absorbed component obtained from spectral fit stays at about 1 × 1023 cm−2 when the intensity of the non-absorbed component is above about 20% of the persistent intensity, but increases to 1 × 1024 cm−2 at the bottom of the dip. The electron-scattering optical depth of the accretion-disk corona and the column density of the absorber are roughly consistent with the double-phase model of X-ray irradiated accretion matter.