In this paper an asymptotic solution of the spherical harmonics equations describing the charge transport in semiconductors is found. This solution is compared with a numerical…
Abstract
In this paper an asymptotic solution of the spherical harmonics equations describing the charge transport in semiconductors is found. This solution is compared with a numerical solution for bulk silicon device. We also indicate application of this solution to the construction of high field hydrodynamical models.
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Giovanni Mascali and Vittorio Romano
This paper intends to present a hydrodynamical model which describes the hole motion in silicon and couples holes and electrons.
Abstract
Purpose
This paper intends to present a hydrodynamical model which describes the hole motion in silicon and couples holes and electrons.
Design/methodology/approach
The model is based on the moment method and the closure of the system of moment equations is obtained by using the maximum entropy principle (hereafter MEP). The heavy, light and split‐off valence bands are considered. The first two are described by taking into account their warped shape, while for the split‐off band a parabolic approximation is used.
Findings
The model for holes is coupled with an analogous one for electrons, so obtaining a complete description of charge transport in silicon. Numerical simulations are performed both for bulk silicon and a p‐n junction.
Research limitations/implications
The model uses a linear approximation of the maximum entropy distribution in order to close the system of moment equations. Furthermore, the non‐parabolicity of the heavy and light bands is neglected. This implies an approximation on the high field results. This issue is under current investigation.
Practical implications
The paper improves the previous hydrodynamical models on holes and furnishes a complete model which couples electrons and holes. It can be useful in simulations of bipolar devices.
Originality/value
The results of the paper are new since a better approximation of the band structure is used and a description of both electron and hole behavior is present, therefore the results are of a certain relevance for the theory of charge transport in semiconductors.
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In this paper we consider the Boltzmann equation describing the carrier transport in a semiconductor. A modified Chapman‐Enskog method is used, in order to find approximate…
Abstract
In this paper we consider the Boltzmann equation describing the carrier transport in a semiconductor. A modified Chapman‐Enskog method is used, in order to find approximate solutions in the weakly non‐homogeneous case. These solutions allow us to calculate the mobility and diffusion coefficients as functions of the electric field. The integral‐differential equations derived by means of the above mentioned method are numerically solved using a combination of spherical harmonics functions and finite‐difference operators. The Kane model for the electron band structure is assumed; the parabolic band approximation is obtained as a particular case. The numerical values of the mobility and diffusivity in a silicon device are compared with experimental data. The Einstein relation is also shown.
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Giovanni Mascali and Vittorio Romano
On the basis of the maximum entropy principle, seeks to formulate a hydrodynamical model for electron transport in GaAs semiconductors, which is free of any fitting parameter.
Abstract
Purpose
On the basis of the maximum entropy principle, seeks to formulate a hydrodynamical model for electron transport in GaAs semiconductors, which is free of any fitting parameter.
Design/methodology/approach
The model considers the conduction band to be described by the Kane dispersion relation and includes both Γ and L valleys. Takes into account electron‐non‐polar optical phonon, electron‐polar optical phonon and electro‐acoustic phonon scattering.
Findings
The set of balance equation of the model forms a quasilinear hyperbolic system and for its numerical integration a recent high‐order shock‐capturing central differencing scheme has been employed.
Originality/value
Presents the results of simulations of n+ ‐n‐n+ GaAs diode and Gunn oscillator.
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Maria Torres Vega, Vittorio Sguazzo, Decebal Constantin Mocanu and Antonio Liotta
The Video Quality Metric (VQM) is one of the most used objective methods to assess video quality, because of its high correlation with the human visual system (HVS). VQM is…
Abstract
Purpose
The Video Quality Metric (VQM) is one of the most used objective methods to assess video quality, because of its high correlation with the human visual system (HVS). VQM is, however, not viable in real-time deployments such as mobile streaming, not only due to its high computational demands but also because, as a Full Reference (FR) metric, it requires both the original video and its impaired counterpart. In contrast, No Reference (NR) objective algorithms operate directly on the impaired video and are considerably faster but loose out in accuracy. The purpose of this paper is to study how differently NR metrics perform in the presence of network impairments.
Design/methodology/approach
The authors assess eight NR metrics, alongside a lightweight FR metric, using VQM as benchmark in a self-developed network-impaired video data set. This paper covers a range of methods, a diverse set of video types and encoding conditions and a variety of network impairment test-cases.
Findings
The authors show the extent by which packet loss affects different video types, correlating the accuracy of NR metrics to the FR benchmark. This paper helps identifying the conditions under which simple metrics may be used effectively and indicates an avenue to control the quality of streaming systems.
Originality/value
Most studies in literature have focused on assessing streams that are either unaffected by the network (e.g. looking at the effects of video compression algorithms) or are affected by synthetic network impairments (i.e. via simulated network conditions). The authors show that when streams are affected by real network conditions, assessing Quality of Experience becomes even harder, as the existing metrics perform poorly.
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Antonio Chella, Marilia Liotta and Irene Macaluso
The aim of this paper is to integrate perception, action and symbolic knowledge to allow an autonomous robot to operate in unstructured environments and to interact with…
Abstract
Purpose
The aim of this paper is to integrate perception, action and symbolic knowledge to allow an autonomous robot to operate in unstructured environments and to interact with non‐expert users.
Design/methodology/approach
To achieve such goals, a cognitive robot architecture is proposed based on the integration between subsymbolic and linguistic computations through the introduction of an intermediate level of representation based on conceptual spaces.
Findings
The architecture has been tested in the CiceRobot project on tasks related to guided tours in the Archaeological Museum of Agrigento. Experimental results show that robot cognitive behaviors allow one to achieve a full functional robotic museum guide. In particular, through the interaction with visitors the robot is able to customize the tour depending on their preferences.
Originality/value
The paper presents a significant case study because it involves perception, planning and human‐robot interaction. The proposed architecture addresses the capacities which are generally addressed by an intelligent agent: the capability of representing itself and the external world, of imagining possible evolutions of the world, of paying attention to the relevant events, of planning and evaluating situations and actions.
The effects of failure mode and strain conditions of CFRP, concrete and stirrups on the shear capacity of reinforced beams bonded by geopolymer and epoxy are studied. In addition…
Abstract
Purpose
The effects of failure mode and strain conditions of CFRP, concrete and stirrups on the shear capacity of reinforced beams bonded by geopolymer and epoxy are studied. In addition, a prediction model of the ultimate bearing capacity of CFRP-shear-strengthened beams is proposed, which considers adhesive performance parameters adhesive performance parameter ßE and FRP width parameter ßw.
Design/methodology/approach
This paper presents an experimental study on ultimate bearing capacity of CFRP-shear-strengthened pre-cracked beams with geopolymer and epoxy resin, which considers parameters such as impregnated adhesives types and CFRP-strengthened scheme.
Findings
The failure modes of CFRP-strengthened beams bonded by geopolymer are the combination of the CFRP-concrete interface substrate failure and fracture failure of CFRP, and that of epoxy is the local substrate failures with small area. The ultimate load of CFRP-strengthened beams is directly affected by the failure modes. The ultimate bearing capacity of CFRP-strengthened beams with geopolymer is 91.4% of that of epoxy resin. Compared with ultimate bearing capacity of CFRP-strengthened beams with U-shaped, that of complete-wrapping increases by 2.5%. Moreover, the stirrup peak strain is reduced by more than 30% in CFRP-strengthened beams bonded with geopolymer and epoxy resin in comparison with the unstrengthened beam. The existing prediction model cannot accurately predict the CFRP shear capacity contribution of strengthened beams with different CFRP-strengthened schemes and adhesive properties. The estimated results are much lower than the test data, and the deviation is much larger than 20%.
Originality/value
Geopolymer alternative to epoxy as an adhesive is feasible and effective for CFRP reinforcement. Furthermore, the accuracy is improved by introducing parameters about adhesive properties based on the existing prediction model. The estimated results are in excellent agreement with the test data, and the deviation is controlled within −12.80%, and the model is suitable for predicting the shear capacity of FRP-strengthened beams with ßf = 90° in shear capacity database.
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Purpose – To outline new research on the ways in which older athletes incorporate drinking practices into their social and sporting identities. Drawing on research with older…
Abstract
Purpose – To outline new research on the ways in which older athletes incorporate drinking practices into their social and sporting identities. Drawing on research with older Australian athletes, the chapter asks us to re-imagine the sport–alcohol nexus to include new sites and subjects that can shed light on wider articulations of the pleasurable and problematic relationships between sport, alcohol and social identity.
Design/methodology/approach – In the first part of the chapter, key themes in sport and ageing research are discussed. In the second, issues of alcohol, older age and sporting identities are considered, drawing on research at the 2017 Australian Masters Games. This sets the scene for a fuller discussion and analysis of some of the missed opportunities in alcohol and sport research, and their implications for sport and social policy, health promotion and social care more broadly.
Findings – The chapter reveals several under-developed opportunities in a broader research agenda on sport and alcohol, including the role alcohol plays in conferring membership and belonging to the sporting communities of older athletes. The chapter suggests that a recalibration of popular understandings of sport, ageing and alcohol – both as separate and as inter-related concerns – may provide an opportunity for addressing wider social concerns with ageing more broadly.
Research limitations/implications – Discussion of ageing and alcohol, through the lens of sport, has important implications for an analysis of drinking practices and in sport, and for sport and social policy, health promotion and social care.
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Sabiha Barour and Abdesselam Zergua
This paper aims to analyze the performance of reinforced concrete (RC) beams strengthened in shear with carbon fiber-reinforced polymer (CFRP) sheets subjected to four-point…
Abstract
Purpose
This paper aims to analyze the performance of reinforced concrete (RC) beams strengthened in shear with carbon fiber-reinforced polymer (CFRP) sheets subjected to four-point bending.
Design/methodology/approach
ANSYS software is used to build six models. In addition, SOILD65, LINK180, SHELL181 and SOLID185 elements are used, respectively, to model concrete, steel reinforcement, polymer and steel plate support. A comparative study between the nonlinear finite element and analytical models, including the ACI 440.2 R-08 and FIB14 models as well as experimental data, is also carried out.
Findings
The comparative study of the nonlinear finite element results with analytical models shows that the difference between the predicted load capacity ranges from 4.44%–24.49% in the case of the ACI 440.2 R-08 model, while the difference for FIB14 code ranges from 2.69%–26.03%. It is clear that there is a good agreement between the nonlinear finite element analysis (NLFEA) results and the different expected CFRP codes.
Practical implications
This model can be used to explore the behavior and predict the RC beams strengthened in shear with different CFRP properties. They could be used as a numerical platform in contrast to expensive and time-consuming experimental tests.
Originality/value
On the basis of the results, a good match is found between the model results and the experimental data at all stages of loading the tested samples. Load capacities as well as load deflection curves are also presented. It is concluded that the differences between the loads at failure ranged from 0.09%–6.16% and 0.56%–4.98%, comparing with experimental study. In addition, the increase in compressive strength produces an increase in the ultimate load capacity of the beam. The difference in the ultimate load capacity was less than 30% when compared with the American Concrete Institute and FIB14 codes.
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As the field of leadership education continues to prioritize learning in leadership, it is important to ask the question: What do we know about the learning process itself…
Abstract
As the field of leadership education continues to prioritize learning in leadership, it is important to ask the question: What do we know about the learning process itself? Conceptual change, a learning framework used in educational psychology, can help to explain learning in leadership. Research on conceptual change in the social sciences is emergent and ripe for further exploration. Until the results of such research are readily available, there are some pedagogical tools produced by conceptual change researchers that leadership educators might find valuable in curriculum design. This paper introduces conceptual change theory and research to leadership educators as a viable framework from which to research learning in leadership, and presents pedagogical tools that encourage deeper learning through conceptual change