Jackson Model Research Articles

On the role of nonlinearities in the Boussinesq-type wave equations

Longitudinal mechanical waves in biomembranes are described by a Boussinesq-type wave equation. It is shown that in this case the nonlinearities are of a different type compared with conventional models of solids. The governing equation analysed in this paper is the improved Heimburg–Jackson model with two dispersive terms. The soliton-type solutions of such a wave equation are found and analysed. The existence of solitons depends on the ratio of nonlinear terms and the width of solitons is governed by dispersive terms.

Kinetic block model of crystal–mother‐phase interface with preferential clustering ‐ single layer case

A new single‐layer kinetic block model of crystal growth is proposed, which takes into account preference for bonds between blocks of the same type over mixed‐type bonds. The obtained parameters describing stable growth conditions were compared with other theoretical models (such as thermodynamic Jackson model and the earlier proposed kinetic model based on zeroth order approximation) which assume that new growth units are attached in a completely random way. Additionally, the results were compared with Monte Carlo simulations. The proposed model produced results which matched the simulation results much better than the other theoretical models. The new model can be used for studying crystal growth both from solution and from vapour. Calculations based on this model show that the number of created mixed‐type bonds depends on the temperature and is lower from its estimation obtained with the use of the zeroth order (Bragg‐Williams) approximation.

The impact of life events on the tourism behaviour of senior citizens in Freising, Germany

Goal and objectives of the dissertationGoalTo gain a better understanding of seniors' tourism behaviour and to uncover the meanings behind travelling in later years.Objectives* to gain a comprehensive understanding of the impact of life events on seniors' tourism behaviour* to understand the development of travel behaviour over the life course* to discover variances in senior travel behaviour caused by identifiable life events* to understand why seniors cease travelling* to contribute to the methodological body of knowledge by applying qualitative biographic research methods to investigate seniors' tourism behaviour* to contribute to academic theory by applying an interdisciplinary approach of tourism social sciences, gerontology and human development* to contribute to academic theory by merging tourism constraint and facilitator models with an ecological perspectiveMethodologyExisting research on seniors' tourism behaviour largely focuses on quantitative measures and does not reflect the diverse nature of seniors. For this reason a real-life event approach was applied to investigate seniors' tourism behaviour in depth.The research paradigm adopted in this thesis followed a critical realist and pragmatist ontology which is informed by a post-positivist research philosophy. The research draws on a multiple case study and was conducted between October 2011 and September 2012 with 23 seniors aged 60 years and older living in Freising, Germany. This thesis combined two sets of semi-structured face-to-face in-depth biographic interviews in order to improve and validate the retrieved data from the first interview phase. The analytical framework includes the identification of travel periods, a within-case and a cross-case thematic analysis.ResultsThe thesis identified a number of live events and life-event-related factors which can affect the tourism behaviour of seniors including: deteriorating health, age-psychological factors, detachment from children, pets as family members, migration and visiting friends and family, the living environment, grandparenthood, illness of the spouse and nursing obligations, the loss of the spouse, meeting a new partner, working commitments and retirement, and inheritance.Findings of the study showed that the impact of life events on the tourism behaviour of seniors is diverse and dependent on conditions and living circumstances. Travel distances and durations and tourism activities for example can increase decrease or stagnate. Similarly, motivations are manifold and seniors travel for a variety of reasons such as seeking experiences, socialization, relaxation or having a last meaningful travel experience.The thesis found that tourism plays a significant role in successful aging strategies and can contribute to life satisfaction and individual well-being in old age. Minor evidence was found that could support theories of disengagement. Only those who found themselves socially isolated showed signs of active disengagement from society. These seniors, who had been socially isolated by unfortunate circumstances, simultaneously experienced other constraints and largely ceased their tourism participation.Theoretical conclusionsThis thesis suggests that seniors' tourism behaviour can be explained by ecological constraints and facilitators and translated Crawford et al.'s (1991) and Jackson's (2005) hierarchical leisure constraints model into the senior tourism context. The generated advanced constraints and facilitators model of senior tourism behaviour based on a number of propositions regarding properties of life events and their relationships to other concurring factors. The structure of the model conforms to Crawford, Jackson, and Godbey's (1991) original leisure constraints concept in many aspects. Tourism behaviour is formed by travel preferences which are constrained and negotiated on intrapersonal, interpersonal and structural levels. …

Stability and Instability of Improved Heimburg{Jackson Model to Nerve Pulse Propagation

There are a number of mathematical models to nerve pulse propagation in biomembranes, as Hodgkin--Huxley, FitzHugh--Nagumo and Heimburg--Jackson models, see, e.g., [1,2]. However, these models do not describe adequately all observed phenomena.Recently in [2], generalized Boussinesq equation with quadratic--cubic nonlinearity is proposed as an improvement of the well-known Heimburg--Jackson model.In this study we prove analytically the orbital stability and instability of solitary waves to the improved Heimburg--Jackson model (1). The results depend on the relationship between all parameters of the model. For the set of data, obtained experimentally, our theoretical results are in full agreement with the numerical simulations, presented in [3].

A two-phase shallow debris flow model with energy balance

This paper proposes a thin layer depth-averaged two-phase model provided by a dissipative energy balance to describe avalanches of solid-fluid mixtures. This model is derived from a 3D two-phase model based on the equations proposed by Jackson [R. Jackson, The Dynamics of Fluidized Particles, 2000] which takes into account the force of buoyancy and the forces of interaction between the solid and fluid phases. Jackson's model is based on mass and momentum conservation within the two phases, i.e. two vector and two scalar equations. This system has five unknowns: the solid volume fraction, the solid and fluid pressures and the solid and fluid velocities, i.e. three scalars and two vectors. As a result, an additional equation is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work. In particular, Pitman and Le [E.B. Pitman, L. Le, Phil. Trans. R. Soc. A, 2005] replaced this closure simply by imposing an extra boundary condition. If the pressure is assumed to be hydrostatic, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here a closure equation to complete Jackson's model, imposing incompressibility of the solid phase. We prove that the resulting whole 3D model is compatible with a dissipative energy balance. From this model, we deduce a 2D depth-averaged model and we also prove that the energy balance associated with this model is dissipative. Finally, we propose a numerical scheme to approximate the depth-averaged model. We present several numerical tests for the 1D case that are compared to the results of the model proposed by Pitman and Le.

Bifurcation analysis in a diffusive Segel–Jackson model

Bifurcations of spatially nonhomogeneous periodic orbits and steady state solutions are rigorously proved for a reaction–diffusion system modeling predator–prey interaction. The existence of these patterned solutions shows the richness of the spatiotemporal dynamics such as oscillatory behavior and spatial patterns.

Thermodynamic Studies on Solid Dispersions of Nicotinamide – Khellin Drug System

Biomolecules, nicotinamide (NA), and khellin (KH) have been used orally for a number of diseases for the last few decades. NA is shown as an HIV, Mycobaterium tuberculosis, and pellagra preventive agent, whereas KH is used in renal colic, diuretic, kidney stone, coronary, bronchial asthma, angina, vitiligo, and psoriasis. In recent years, research on solid dispersions of binary drug products is playing a significant role in the drug delivery process of the pharmaceutical industries. The present study highlights the thermodynamic characteristics of solid dispersions binary products of active pharmaceutical ingredient KH with pharmaceutical excipient NA. These products have been prepared through melting/fusion method. The solid–liquid equilibrium (SLE) data of NA–KH system favors the formation of an eutectic (E) at 0.135 mole fraction of KH and melting temperature 120.6°C and noneutectic solid dispersions (A1–A8) at their defined compositions and temperatures. To illustrate the molecular interaction, the activity coefficient model based on enthalpy of fusion is employed to calculate the excess partial and integral thermodynamic functions such as gE, hE, and sE. The positive value of excess Gibbs free energy predicts the stronger molecular interaction between the like molecules as compared to unlike molecules. The spontaneity of mixing of eutectic and noneutectic alloys was discussed by the integral mixing quantities ΔGM, ΔHM, and ΔSM. The value of critical radius (r*) of solid dispersions is found in nanometer (nm) scale, which suggests the process of solidification for nanosolid dispersions, and it is very surprising for the pharma world. The binary interface structure of alloys has been discussed in light of the Jackson model of interface structure.

Mechanisms underlying REBT in mood disordered patients: Predicting depression from the hybrid model of learning

Jackson's (2005, 2008a) hybrid model of learning identifies a number of learning mechanisms that lead to the emergence and maintenance of the balance between rationality and irrationality. We test a general hypothesis that Jackson's model will predict depressive symptoms, such that poor learning is related to depression. We draw comparisons between Jackson's model and Ellis' (2004) Rational Emotive Behavior Therapy and Theory (REBT) and thereby provide a set of testable learning mechanisms potentially underlying REBT. Results from 80 patients diagnosed with depression completed the learning styles profiler (LSP; Jackson, 2005) and two measures of depression. Results provide support for the proposed model of learning and further evidence that low rationality is a key predictor of depression. We conclude that the hybrid model of learning has the potential to explain some of the learning and cognitive processes related to the development and maintenance of irrational beliefs and depression.

Comparison of thermodynamic and kinetic models of single‐layer crystal–mother‐phase interface

AbstractSimple analytical kinetic model of single‐layer crystal–mother‐phase interface is proposed, which provides results that can be compared directly with thermodynamic Jackson model. Both models are based on zeroth order approximation known from lattice‐gas models, in which solid and fluid growth units are treated as mixed randomly in the interface layer. It is shown that the kinetic and thermodynamic approaches can lead to very similar predictions about growth mechanism. The parameters characterising growth conditions, obtained from these models, are significantly different from those obtained from Monte Carlo simulations applied to study stable states of single‐layer interface. Monte Carlo calculations describe crystal growth in detail and their results can predict characteristic parameters for real experiment. Observed differences seem to be strongly influenced by the use of zeroth order approximation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Recruiting higher education students: a systematic review of the college selection process models

The study of student enrolment decision-making or college choice behaviour is an extremely practical operation that leads to greater efficiency and effectiveness. Understanding student college choice behaviour enables institutions of higher learning to estimate the probability of student interest and enrolment. Higher education institutions (HEIs) would be able to strategise their marketing efforts in the scramble for students. This paper seeks to review systematically the student college choice models. The models to be reviewed are Chapman model (1981), Hanson and Litten model (1982), Jackson model (1982) and Hossler and Gallagher model (1987). It is suggested that future research should investigate on ‘campus security’ on student decision making in college enrolment as it has not been empirically studied in the models abovementioned. Furthermore, future empirical research can also be carried out on prospective students, i.e., students who have yet to enrol in HEI in Southeast Asia countries.

Effect of temperature on an elastic-plastic hemispherical asperity in contact with a rigid flat

The majority of surface effects are temperature dependent. The present work extends the Jackson and Green model (2005) for an elastic-plastic hemispherical asperity in contact with a rigid flat by including the temperature effects. The result initially shows that there is no change in end of elastic-plastic state or start of fully plastic regime when temperature increases at the contacting interfaces. But in practical applications, temperature effect plays an important role in determining the state transition. There is no change in the state transition from the present FEA results, because FEM packages utilize the elastic properties (E) and the yield strength (Y) as constant for the entire analysis. But the elastic modulus and yield will vary when the temperature is increasing. So, a methodology is presented and validated with the experimental observations in this paper to evaluate the variations in E/Y ratio with increasing temperature using the finite element concepts.

On the minimum fluidization velocity in 2D fluidized beds

In the present study, a new correlation for the determination of the minimum fluidization velocity in 2D fluidized beds was developed. The proposed correlation was based on the experimental results obtained in 2D fluidized beds with different particle sizes, bed thicknesses and bed heights. Thus, the proposed correlation depends only on the nondimensional variable t/dp, where t is the bed thickness and dp is the particle size. The proposed correlation was compared with other experimental results that can be found in the literature, and two different trends were observed. Namely, one set of experimental results was in accordance with the proposed correlation, while the other set deviated from the theoretical results. In particular, the minimum fluidization velocities of the experimental results were greater than the predicted values of the proposed correlation. In view of the differences in the experimental conditions, the observed discrepancies may be attributed to the effects of electrostatic charge and particle shape. In addition, the experimental fluidization–defluidization curves were compared to the theoretical results of Jackson's model, and the parameters were fitted to the experimental data. However, Jackson's model is based on a 1D bed; thus, general parameters could not be obtained for a bed with a fixed particle size and thickness due to the two dimensional voidage distribution in the bed and bed cohesion effects, which are a result of electrostatic forces and are not considered in Jackson's model.

Hierarchical Leisure Constraints on Leisure Motivation and Participation among Security Agent

This research looks close the effect of security agent's hierarchical leisure constraint on the leisure motivation and participation based on the Jackson's Model of the hierarchical leisure constraints. This research selected 420 people for sampling, designating security agents who work for security companies located in Seoul in 2009 at present as subjects by utilizing purposive sampling method, but the number of sampling used for ultimate analysis is 356. In this research, reliability analysis's and structural equation modeling's Maximum Likelihood method are used to prove the reliability and validity of questionnaire. By using these research method and procedures, the conclusion of this research is as following. First, intra-personal leisure constraint was affected by interpersonal, structural leisure constraint. Second, leisure motivation was affected negatively by leisure constraint. Third, leisure participation was affected positively by leisure motivation. Synthesizing all things referred above, leisure constraint was affected by inter-personal, structural leisure constraint, and in turn, leisure motivation and leisure participation were affected by its effects. It turned out that leisure motivation has a meaningful effect on leisure participation through leisure participation and adjusting process.

Gas–solid flow hydrodynamics of an industrial scale catalyst lift engager

This study characterizes the hydrodynamics of an industrial scale lift engager which circulates the catalyst between the reactor and regenerator sections of a continuous catalytic reformer in an oil refinery. The flow of Geldart D particles in this unit was simulated using a granular Eulerian model. Before studying the influence of the operating parameters, the effect of several model parameters such as the drag and the frictional pressure models on the predictions was carried out. Whilst all of the drag models investigated in this study (Gidaspow and Syamlal–O’Brien models) gave qualitatively similar results, the choice of the frictional pressure model affected the simulation results in a rather astounding manner. The KTGF based frictional pressure model gave inconsistent results as both catalyst velocity and its volume fraction increased along the lift line. However, the Johnson and Jackson model overcame this drawback. Interestingly, both KTGF based and Johnson and Jackson models gave similar results for the flow inside a simple riser. Therefore, it can be concluded that for complex flow domains having both dilute and dense phase flows, the most widely used KTGF model may not be appropriate and Johnson and Jackson model should be used instead. After optimizing the selection of model parameters, simulations were conducted to study the effect of the lift gas velocity. It was observed that a lower lift gas velocity leads to large-scale fluctuations in the outlet mass flow rate. The simulation results were also compared with the previously reported studies on the riser flow with a reasonable qualitative agreement.

The lowest of low-cost carriers: the case of AirAsia

In December 2001, just a few months after the terrorist attacks on New York and Washington left the international airline industry reeling, a new Malaysian company called ‘Tune Air’ purchased a small underperforming domestic Malaysian airline known as ‘AirAsia’ for 1 Malaysian ringgit and the assumption of 40 million ringgit in debt. Within 11 months of acquiring the company, Tune Air had fully repaid this debt and by January 2003 the company was operating six aircraft domestically. In 2006, AirAsia boasted a fleet of 35 Boeing 737-300 aircraft and eight Airbus 320 aircraft with orders for 100 more A320s (Vietnam News 2006) and was forecast to carry nine million passengers to 52 domestic and international destinations. AirAsia's meteoric rise is the result of the confluence of opportunity and skillful application of the low-cost Carrier (LCC) aviation business model. This model, which has its origins in the success of Southwest Airlines (see Gittell 2003) and Michael O'Leary's ‘Ryanair’, has been implemented around the world and consists of a number of common elements such as reduced inflight service, point to point travel, high aircraft utilization, single fleet type, ticketless passenger reservation systems and considerable functional flexibility in staffing. In this article we trace the rise of AirAsia's success and the nuances of the low-cost aviation model it has pursued. We draw upon established theory from the fields of strategy and strategic human resource management to explain AirAsia's minimalist approach to human resource management. In particular, we apply Porter's (1985) well known theory of generic business strategies and Schuler and Jackson's model linking HR practices to competitive strategy, to argue that the airline's successful quest for market cost leadership has been supported by a strict focus on Legge's (1995) ‘hard’ variety of HRM. It is further argued that while a number of the components of the Southwest Airlines model are evident, there are also significant differences in AirAsia's management of human resources. In particular, it is argued that the airline has adopted a far stronger cost minimization and ‘hard’ HRM path that is closer to Ryanair's model, which has proved highly successful for the airline in South East Asia.

Comparing different approach and avoidance models of learning and personality in the prediction of work, university, and leadership outcomes

Jackson (2005) developed a hybrid model of personality and learning, known as the learning styles profiler (LSP) which was designed to span biological, socio-cognitive, and experiential research foci of personality and learning research. The hybrid model argues that functional and dysfunctional learning outcomes can be best understood in terms of how cognitions and experiences control, discipline, and re-express the biologically based scale of sensation-seeking. In two studies with part-time workers undertaking tertiary education (N = 137 and 58), established models of approach and avoidance from each of the three different research foci were compared with Jackson's hybrid model in their predictiveness of leadership, work, and university outcomes using self-report and supervisor ratings. Results showed that the hybrid model was generally optimal and, as hypothesized, that goal orientation was a mediator of sensation-seeking on outcomes (work performance, university performance, leader behaviours, and counterproductive work behaviour). Our studies suggest that the hybrid model has considerable promise as a predictor of work and educational outcomes as well as dysfunctional outcomes.

Performances of a multistatic model of sound scattering by rough surfaces

The ocean floor is far from being a smooth and perfectly rigid surface. That is why its sound scattering properties are a useful input to the analysis of this medium as for acoustic data inversion. Thus, multi‐static scattering coefficients have been investigated in a frequency range of order of 10 kHz to 300 kHz. The Kirchhoff Approximation and the Small Perturbation Method could be cited respectively in the case of dimensions of a rough surface larger and smaller than the wavelength. Nevertheless, for those frequencies, hence for those wavelengths, a rough surface should be considered at different scales compared to the wavelength. As a part of the incident wave is transmitted to the seabed medium, it is also important to know the effect of the scattering coming from the volume. Jackson's scattering model takes these considerations into account. The aim of the study is first to show an improvement of the surface scattering method using the Small Slope Approximation and keeping the initial method of Jackson's model to describe the scattering from the volume. Comparisons with well‐known models are presented to show the performances of this new approach and comparisons between different multistatic geometries are analyzed to show the most useful configuration of the model.

Piezoelectric spectroscopic studies of Zn1-x-yBexMnymixed crystals

This paper presents results of experimental and theoretical piezoelectric studies of a group of mixed crystals of the type Zn1 - x - yBexMnySe. The fittings of theoretical to experimental amplitude and phase piezoelectric spectra were performed in a modified Jackson and Amer model. The influence of the surface treatment such as grinding, polishing and etching on the PZE spectra is analysed in the model of surface defects applied for the interpretation of the spectra for energies of photons below the energy gap of the crystal.

Modeling Transmission of Microwaves Through Dynamic Vegetation

In this paper, we develop a model for estimating canopy opacity tau for sweet corn. We estimate the refractive index based upon moisture distribution in the corn during different stages of growth. The moisture distribution was observed during two season-long field experiments. We found that the moisture content decreased linearly as the height of the corn increased, with the distribution closer to Gaussian in the fruit region during reproductive stages. The tau obtained from our model was compared to that estimated using a widely used Jackson model. In general, our tau estimates were higher than those obtained using the Jackson model, with a root mean-square difference (rmsd) of up to 0.23 Np between the two models. The tau values were used in a microwave emission model at C-band, and the model estimates of brightness were compared with field observations. We found that the model brightness temperatures matched well with observations, with rmsd values of 5.13 and 4.88 K, using our model and the Jackson model for tau, respectively.

Microstructural evolution and metastable phase formation in laser ablation-deposited films of Fe-rich Fe–Ge intermetallic compounds

Thin films of Fe-rich Fe–18 at% Ge and Fe–25 at% Ge were deposited by a pulsed laser ablation technique on single crystal NaCl substrates at room temperature to study phase evolution using transmission electron microscopy. As-deposited films contain nano-scale clusters embedded in a featureless matrix. Quadrupole mass spectrometric observations of the laser-ablated plume show the presence of charged clusters. During in situ heating of the films, the fine-scale clusters grow and profuse crystallization to a bcc FeGe solid solution occurs. For Fe–25 at% Ge thin film, crystallized bcc grains undergo two ordering transitions, viz. bcc → B2 → DO3, during subsequent cooling to room temperature. However, in the case of Fe–18 at% Ge thin film, crystallization leads to formation of the disordered bcc phase. Growth morphologies of the crystals formed during heat treatment indicate faceted growth form, which has been explained by using Jackson's interface model.