Harrison Model Research Articles

Does eco-innovation stimulate employment? The case of Spanish manufacturing firms

The demand for eco-products due to the exigency of friendly and environmental production could affect the employment of the firms. This paper tests whether product and process eco-innovations boost employment in Spain differentiating by the environmental goals (material and energy efficiency and environment responsiveness), by the level of qualification of the workers, and by the dirtiness of the industries. We apply a Green Harrison model, using the Technological Innovation Panel (PITEC) for Spain from 2008 to 2016. Results show a positive relationship between all types of product eco-innovations and employment, while the influence of process eco-innovations on employment depends on the environmental goals, the level of skills, and the industry. Specifically, distinguishing by industry there is a labour-saving effect in clean industries and a labour-friendly effect for low-skilled employment in dirty industries.

An Alternative Formulation of the Harrison Model

The approach advanced by Harrison puts in the spotlight the fundamental role of bistability in hysteresis modeling. The description is based on physical premises concerning irreversible thermodynamics. In the original model, the upscaling of irreversible phenomena acting on the micromagnetic level is carried out by the introduction of a phenomenological parameter β. In the present paper, an alternative approach is proposed. The outputs of individual outputs of elementary hysteresis units (hysterons) are considered like in the stop model. A verification of the proposed model is carried out using measurement data for a praseodymium–dysprosium ribbon sample and a cylinder core made of cobalt-based amorphous material.

Exact Expressions for Lightning Electromagnetic Fields: Application to the Rusck Field-to-Transmission Line Coupling Model

An exact analytical expression for the electric field of the return stroke as excited by a propagating step current source is derived in this paper. This expression could be advantageously used to evaluate the disturbances caused by lightning on overhead lines. There are three equivalent procedures to evaluate the voltages induced by lightning on power lines, namely, the Agrawal–Price–Gurbaxani model, the Taylor–Satterwhite–Harrison model, and the Rachidi model. In the case of a vertical return stroke channel, the coupling model developed by Rusck becomes identical to these three coupling models. Due to its simplicity, the Rusck model is frequently used by engineers to study the effects of lightning on power distribution and transmission lines. In order to reduce the time involved in the electromagnetic field calculation, the Rusck model is incorporated with an analytical expression for the electromagnetic fields of the return stroke excited by a propagating step current pulse. Our research work shows that the Rusck expression can be used to calculate the peak values of lightning induced voltages to an accuracy of about 10%. However, the use of this analytical expression to calculate the time derivatives of lightning induced voltages may result in errors as large as 50%. The derived expression in this paper can be used to correct for this inaccuracy. We also provide an exact expression for the electric field at any given point in space when the propagating current is an impulse function. This expression can be combined with the convolution integral to obtain the electric field corresponding to waveforms similar to measured return stroke currents.

Modeling of Magnetic Properties of Rare-Earth Hard Magnets

Magnetic properties of hard magnets are currently attracting a great deal of attention. In the paper, the modified Harrison model was used to describe the saturating hysteresis loops of three praseodymium–dysprosium ribbons that differed in their chemical composition and processing conditions. Microstructural studies (TEM and diffraction patterns) were performed for the ribbons under consideration. The Harrison model incorporates a number of physically tangible concepts such as the anhysteretic curve, bifurcations, and bi-stability. The modification of the original approach consisted of adding an additional degree of freedom in the modeling by freeing the restraints present in the original version, in which both coercivity and remanence are functions of temperature only.

Modeling the Effect of Compressive Stress on Hysteresis Loop of Grain-Oriented Electrical Steel

Modeling of hysteresis loops may be useful for the designers of magnetic circuits in electric machines. The present paper focuses on the possibility to apply the Harrison model to describe hysteresis loops of grain-oriented electrical steel subject to compressive stress. The model extension is achieved by introduction of an additional term into the equation that describes irreversible magnetization process. The extension term does not include a product of stress and magnetization, as could be anticipated from Sablik’s theory, applicable, e.g., to the Jiles–Atherton model. The present contribution points out the fundamental differences between the two aforementioned modeling approaches, which are based on different philosophies despite some apparent similarities. The modeling results are in a qualitative agreement with the experimental results obtained from a single sheet tester for a representative commercially available grain-oriented electrical steel grade 0.27 mm thick.

The transport properties of poly(G)-poly(C) DNA oligomers in the Harrison's model

Using the tight-binding Hamiltonian of the Harrison's model and the Landauer-Büttiker formalism, some of the electron transport properties of short poly(G)-poly(C) DNA segments lying between two semi-infinite carbon chains as the nanoleads are investigated. The analytical results of the self-energies due to the leads are represented by solving the discretized form of the one-dimensional Schrödinger's equation. Under the Harrison's model, with considering in-phase overlap between the nearest neighbors' all kinds of atomic orbitals, the influences of more atomic orbitals in central channel and backbone of DNA (according to Fishbone model) on the electron transmission probability are discussed. Transmission probabilities for both the single- and many-orbital states are calculated and compared with each other. Furthermore, the effect of increasing length of the DNA nanowire and the coupling strength of nanolead/DNA interface on transmission probability and the current-voltage (I–V) curves and also the effect of different temperatures of the leads on the I–V characteristics are studied. Our results show that the poly(G)-poly(C) DNA oligomer exhibits a semiconducting behavior and that the vertical coupling strength between base pairs and the sugar-phosphate backbone in poly(G)-poly(C) DNA structure can induce the semiconducting gap.

The Anatomy of Consonance/Dissonance: Evaluating Acoustic and Cultural Predictors Across Multiple Datasets with Chords

Acoustic and musical components of consonance and dissonance perception have been recently identified. This study expands the range of predictors of consonance and dissonance by three analytical operations. In Experiment 1, we identify the underlying structure of a number of central predictors of consonance and dissonance extracted from an extensive dataset of chords using a hierarchical cluster analysis. Four feature categories are identified largely confirming the existing three categories (roughness, harmonicity, familiarity), including spectral envelope as an additional category separate from these. In Experiment 2, we evaluate the current model of consonance/dissonance by Harrison and Pearce by an analysis of three previously published datasets. We use linear mixed models to optimize the choice of predictors and offer a revised model. We also propose and assess a number of new predictors representing familiarity. In Experiment 3, the model by Harrison and Pearce and our revised model are evaluated with nine datasets that provide empirical mean ratings of consonance and dissonance. The results show good prediction rates for the Harrison and Pearce model (62%) and a still significantly better rate for the revised model (73%). In the revised model, the harmonicity predictor of Harrison and Pearce’s model is replaced by Stolzenburg’s model, and a familiarity predictor coded through a simplified classification of chords replaces the original corpus-based model. The inclusion of spectral envelope as a new category is a minor addition to account for the consonance/dissonance ratings. With respect to the anatomy of consonance/dissonance, we analyze the collinearity of the predictors, which is addressed by principal component analysis of all predictors in Experiment 3. This captures the harmonicity and roughness predictors into one component; overall, the three components account for 66% of the consonance/dissonance ratings, where the dominant variance explained comes from familiarity (46.2%), followed by roughness/harmonicity (19.3%).

General Height-Diameter Equation Depending on the Stand Variables, for Eucalyptus benthamii

Abstract The aim of this study was to develop a general applicability equation to represent the hypsometric relationship of Eucalyptus benthamii Maiden et Cambage stands in Irani, Santa Catarina. The data came from a continuous forest inventory, with a simple random sampling design and the Bitterlich method. The functions to represent the hypsometric relationship were adjusted with their parameters linear function of stands variables, based on the Gauss-Newton algorithm. The models were evaluated according to the criteria of adjustment and precision, accuracy and validation. In general, the Harrison model, adjusted with the coefficient “c” linear function of age, dominant diameter and basal area, presented the best statistical performance to represent the hypsometric relationship of Eucalyptus benthamii.

Towards a unified approach to hysteresis and micromagnetics modeling: A dynamic extension to the Harrison model

The hysteresis description advanced by Harrison is static in nature. On the other hand, it seems crucial for some applications to consider how the dynamic effects due e.g. to eddy currents in conductive materials affect the shapes of modeled hysteresis loops. In the paper two possible model extensions are proposed. The approach based on the introduction of an additional term in the so-called effective field yields a better accuracy in comparison to the extension using a term related to relaxation time.

Effect of the off-Diagonal d–d Electron Overlappings on the Effective Pair Interaction in the Equiatomic Cu–Ag Melt

The effect of d electron overlapping between two neighboring atoms, which is off-diagonal in magnetic quantum number, on the effective pair interaction in the equiatomic Cu–Ag melt near the melting temperature is studied within the framework of the Wills–Harrison model. An increase in the fraction of off-diagonal overlapping is shown to increase the first minimum depth and to shift its coordinate to smaller interatomic distances for all three partial pair potentials.

Interplay of orbital hopping and perpendicular magnetic field in anisotropic phase transitions for Bernal bilayer graphene and hexagonal boron-nitride.

We theoretically address the perpendicular magnetic field effects on the electronic phase of Bernal bilayer graphene and hexagonal boron-nitride (h-BN) taking into account the total and orbital-projected electronic bands using the tight-binding parameters in the Harrison model, followed by the Green's function method. First, we confirm that our model is computationally efficient and accurate for calculating the magneto-orbital electronic phase transition by reproducing the semimetallic and insulating treatments of pristine Bernal bilayer graphene and h-BN, respectively. In our model, the magnetic field couples only to the electron spin degrees of freedom (with the same contributions for spin-up and spin-down) due to the low dimension of the systems. Here, the main features of the phase transitions are characterized by the electronic density of states (DOS). We found that sp2-hybridization is destroyed when the systems are immersed in the magnetic field, leading to a phase transition to metal for both systems at strong magnetic fields. While there is no phase transition for bilayer graphene at weak magnetic fields, for the case of bilayer h-BN, an insulator to semiconductor phase transition can be viewed, making h-BN more applicable in industry. In bilayer graphene, the anisotropic phase transition appears as insulator-semiconductor, insulator-metal, and semimetal-metal for s-, {px + py}-, and pz-orbitals, respectively, whereas in the case of bilayer h-BN, one observes the same transitions for {s,pz}-orbitals but insulator-semiconductor for {px + py} orbitals. Generically, our findings highlight that the applied magnetic field manipulates the band structure of bilayer graphene and h-BN, and gives ideas to experimentalists for tuning the electro-optical properties of these materials.

The Harrison Model as a Tool to Study Phase Transitions in Magnetocaloric Materials

The Harrison Model as a Tool to Study Phase Transitions in Magnetocaloric Materials

Magnetic and thermal characteristics of armchair graphene nanoribbons in the two-band Harrison model

In this study, within a two-band tight-binding Harrison Hamiltonian and the Green’s function approach, the influences of both localized σ and delocalized π electrons on the Pauli paramagnetic susceptibility, heat capacity and density of states of armchair graphene nanoribbons with different widths are investigated. Temperature dependence of the paramagnetic susceptibility and electronic heat capacity are compared for s and p orbitals of every width. In the density of states, an extension in the bandwidth and the extra number of Van-Hove singularities are observed. More importantly, a paramagnetic behavior associated with the π electrons could take place. Finally, a Schottky anomaly for the heat capacity is reported. Overall, in this paper, it was observed that both the σ and the π electrons contribute significantly to the aforementioned quantities.

GENERAL HEIGHT-DIAMETER EQUATION WITH BIOLOGICAL ATTRIBUTES FOR Pinus taeda L. STANDS

ABSTRACT The aim of this study was to develop an equation with biological attributes and general applicability, to represent the height-diameter relationship for Pinus taeda L. stands, with and without thinning, in the Middle West region of Santa Catarina state, Brazil. The data came from 652 permanent plots, with 428 to 740 m2, located in forest stands with ages ranging from 4.6 to 35.2 years, in which the total heights of about 20% of the trees were measured, in addition to the dominant trees. The functions developed by Harrison, Michailoff, Prodan and Stoffels & Van Soest were fitted with their parameters linear function of stand variables, based on the Gauss-Newton algorithm. In general, the Harrison model, fitted with the parameter linear function of age (t), site index (S), coefficient of variation of the tree diameters in the plot (CV d ) and basal area of the plot (G), showed the best statistical performance to represent the height-diameter relationship, biological consistency and general applicability for stands of Pinus taeda.

Orbital magneto-electronic heat capacity of hydrogenated graphene in the presence of dilute charged impurity

In this paper, the effect of dilute charged impurity and external magnetic field on orbital-resolved density of states (DOS) and electronic heat capacity (EHC) of a monolayer hydrogenated graphene which is called chair-like graphane is investigated within the Harrison model and Green’s function technique. The self-consistent Born approximation has been implemented to describe the effect of scattering between electrons and dilute charged impurities. Our results show that the graphane is a semiconductor and its band gap decreases with impurity and magnetic field. EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity and magnetic field. Generally, EHC increases with the mentioned parameters. Surprisingly, impurity doping only affects the salient behavior of [Formula: see text] orbital contribution of carbon atoms due to the symmetry breaking.

Discrete particle simulations of bubble-to-emulsion phase mass transfer in single-bubble fluidized beds

A classical Euler–Lagrangian model for gas–solid flows was extended with gas component mass conservation equations and used to obtain fundamental insights into bubble-to-emulsion phase mass transfer in bubbling gas–solid fluidized beds. Simulations of injected single rising bubbles under incipient fluidization conditions were carried out, using Geldart-A and -B particles. Phenomena observed in the simulations and those of various theoretical models used to derive phenomenological models were compared to challenge the assumptions underlying the phenomenological models. The bubble-to-emulsion phase mass transfer coefficients calculated for the simulations using Geldart-B particles were in a good agreement with predictions made using the Davidson and Harrison (1963) model. The bubble-to-emulsion phase mass transfer coefficients for Geldart-A particles were, however, much smaller than the predictions obtained from theoretical models (e.g. Chiba and Kobayashi (1970)). The newly developed model allows a detailed analysis of various hydrodynamic aspects and their effects on the mass transfer characteristics in and around rising bubbles in fluidized beds.

Orbital electronic heat capacity of hydrogenated monolayer and bilayer graphene

The tight-binding Harrison model and Green’s function approach have been utilized in order to investigate the contribution of hybridized orbitals in the electronic density of states (DOS) and electronic heat capacity (EHC) for four hydrogenated structures, including monolayer chair-like, table-like, bilayer AA- and finally AB-stacked graphene. After hydrogenation, monolayer graphene and bilayer graphene are behave as semiconducting systems owning a wide direct band gap and this means that all orbitals have several states around the Fermi level. The energy gap in DOS and Schottky anomaly in EHC curves of these structures are compared together illustrating the maximum and minimum band gaps are appear for monolayer chair-like and bilayer AA-stacked graphane, respectively. In spite of these, our findings show that the maximum and minimum values of Schottky anomaly appear for hydrogenated bilayer AA-stacked and monolayer table-like configurations, respectively.

Free energy of mixing of an Fe–Co liquid alloy taking into account nondiagonal d−d-electron coupling in the framework of the Willis−Harrison model

Within the framework of the Willis−Harrison model, the effect of taking into account d−d-electron couplings nondiagonal in the magnetic quantum number between the neighboring atoms in a transition metal on the partial pair potentials and the free energy of mixing of an Fe–Co liquid alloy near the melting temperature is investigated. It is found that an increase in the fraction of nondiagonal couplings results in a decrease in the depth of the first minimum of the partial pair potentials and in the displacement of its position towards larger r. It is shown that taking this factor into account considerably improves the agreement with experimental data of the concentration dependence of the free energy of mixing of the system under consideration.

Impurity doping effects on the orbital thermodynamic properties of hydrogenated graphene, graphane, in Harrison model

Using the Harrison model and Green's function technique, impurity doping effects on the orbital density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) of a monolayer hydrogenated graphene, chair-like graphane, are investigated. The effect of scattering between electrons and dilute charged impurities is discussed in terms of the self-consistent Born approximation. Our results show that the graphane is a semiconductor and its band gap decreases with impurity. As a remarkable point, comparatively EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity. Generally, EHC and MS increases with impurity doping. Surprisingly, impurity doping only affects the salient behavior of py orbital contribution of carbon atoms due to the symmetry breaking.

Modeling 3D Bubble Heat Transfer in Gas–Solid Fluidized Beds Using the CFD-DEM

Computational fluid dynamics discrete element method simulations of a 3D fluidized bed at nonisothermal conditions are presented. Hot gas injection into a colder bed that is slightly above minimum fluidization conditions is modeled in a 3D square bed containing up to 8 million particles. In this study, bubbles formed in monodisperse beds of different glass particle sizes (0.25, 0.5, 0.75, and 1 mm) and using hot-gas-injection temperatures ranging from 700 to 1100 K are analyzed. Bubble heat-transfer coefficients in 3D fluidized beds are reported and compared with theoretical predictions on the basis of the Davidson and Harrison model.