917 resultados para two-factor models
Resumo:
This paper discusses critical findings from a two-year EU-funded research project involving four European countries: Austria, England, Slovenia and Romania. The project had two primary aims. The first of these was to develop a systematic procedure for assessing the balance between learning outcomes acquired in education and the specific needs of the labour market. The second aim was to develop and test a set of meta-level quality indicators aimed at evaluating the linkages between education and employment. The project was distinctive in that it combined different partners from Higher Education, Vocational Training, Industry and Quality Assurance. One of the key emergent themes identified in exploratory interviews was that employers and recent business graduates in all four countries want a well-rounded education which delivers a broad foundation of key business knowledge across the various disciplines. Both groups also identified the need for personal development in critical skills and competencies. Following the exploratory study, a questionnaire was designed to address five functional business areas, as well as a cluster of 8 business competencies. Within the survey, questions relating to the meta-level quality indicators assessed the impact of these learning outcomes on the workplace, in terms of the following: 1) value, 2) relevance and 3) graduate ability. This paper provides an overview of the study findings from a sample of 900 business graduates and employers. Two theoretical models are proposed as tools for predicting satisfaction with work performance and satisfaction with business education. The implications of the study findings for education, employment and European public policy are discussed.
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It is well known that one of the obstacles to effective forecasting of exchange rates is heteroscedasticity (non-stationary conditional variance). The autoregressive conditional heteroscedastic (ARCH) model and its variants have been used to estimate a time dependent variance for many financial time series. However, such models are essentially linear in form and we can ask whether a non-linear model for variance can improve results just as non-linear models (such as neural networks) for the mean have done. In this paper we consider two neural network models for variance estimation. Mixture Density Networks (Bishop 1994, Nix and Weigend 1994) combine a Multi-Layer Perceptron (MLP) and a mixture model to estimate the conditional data density. They are trained using a maximum likelihood approach. However, it is known that maximum likelihood estimates are biased and lead to a systematic under-estimate of variance. More recently, a Bayesian approach to parameter estimation has been developed (Bishop and Qazaz 1996) that shows promise in removing the maximum likelihood bias. However, up to now, this model has not been used for time series prediction. Here we compare these algorithms with two other models to provide benchmark results: a linear model (from the ARIMA family), and a conventional neural network trained with a sum-of-squares error function (which estimates the conditional mean of the time series with a constant variance noise model). This comparison is carried out on daily exchange rate data for five currencies.
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The procedure for successful scale-up of batchwise emulsion polymerisation has been studied. The relevant literature on liquid-liquid dispersion on scale-up and on emulsion polymerisation has been crit1cally reviewed. Batchwise emulsion polymerisation of styrene in a specially built 3 litre, unbaffled, reactor confirmed that impeller speed had a direct effect on the latex particle size and on the reaction rate. This was noted to be more significant at low soap concentrations and the phenomenon was related to the depletion of micelle forming soap by soap adsorption onto the monomer emulsion surface. The scale-up procedure necessary to maintain constant monomer emulsion surface area in an unbaffled batch reactor was therefore investigated. Three geometrically similar 'vessels of 152, 229 and 305mm internal diameter, and a range of impeller speeds (190 to 960 r.p.m.) were employed. The droplet sizes were measured either through photomicroscopy or via a Coulter Counter. The power input to the impeller was also measured. A scale-up procedure was proposed based on the governing relationship between droplet diameter, impeller speed and impeller diameter. The relationships between impeller speed soap concentration, latex particle size and reaction rate were investigated in a series of polymerisations employing an amended commercial recipe for polystyrene. The particle size was determined via a light transmission technique. Two computer models, based on the Smith and Ewart approach but taking into account the adsorption/desorption of soap at the monomer surface, were successful 1n predicting the particle size and the progress of the reaction up to the end of stage II, i.e. to the end of the period of constant reaction rate.
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A two-factor no-arbitrage model is used to provide a theoretical link between stock and bond market volatility. While this model suggests that short-term interest rate volatility may, at least in part, drive both stock and bond market volatility, the empirical evidence suggests that past bond market volatility affects both markets and feeds back into short-term yield volatility. The empirical modelling goes on to examine the (time-varying) correlation structure between volatility in the stock and bond markets and finds that the sign of this correlation has reversed over the last 20 years. This has important implications far portfolio selection in financial markets. © 2005 Elsevier B.V. All rights reserved.
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Competition between three foliose lichens common on slate rock in south Gwynedd, Wales was studied in the field using a factorial experimental design. The lichens were grown as fragments glued to pieces of slate in two- and three-species mixtures. In the two-species mixtures, Parmelia conspersa (Ehrh. Ex Ach.) Ach. outcompeted Parmelia glabratula ssp. fuliginosa (Fr. ex Duby) Laund. strongly and Physcia orbicularis (Neck.) Poetsch less strongly, while P. orbicularis outcompeted P. glabratula weakly. Significant two-factor interactions indicated that the results from the three-species mixture could not be predicted from the two-species mixtures. Parmelia glabratula and P. orbicularis grew better in the presence of two competitors than one. This result suggests that the three species may co-occur on well-lit rock surfaces at the site.
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We consider return-to-zero (RZ) pulses with random phase modulation propagating in a nonlinear channel (modelled by the integrable nonlinear Schrödinger equation, NLSE). We suggest two different models for the phase fluctuations of the optical field: (i) Gaussian short-correlated fluctuations and (ii) generalized telegraph process. Using the rectangular-shaped pulse form we demonstrate that the presence of phase fluctuations of both types strongly influences the number of solitons generated in the channel. It is also shown that increasing the correlation time for the random phase fluctuations affects the coherent content of a pulse in a non-trivial way. The result obtained has potential consequences for all-optical processing and design of optical decision elements.
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Studies of the determinants and effects of innovation commonly make an assumption about the way in which firms make the decision to innovate, but rarely test this assumption. Using a panel of Irish manufacturing firms we test the performance of two alternative models of the innovation decision, and find that a two-stage model (the firm decides whether to innovate, then whether to perform product only, process only or both) outperforms a one-stage, simultaneous model. We also find that external knowledge sourcing affects the innovation decision and the type of innovation undertaken in a way not previously recognised in the literature. © 2007 Elsevier Ltd. All rights reserved.
Resumo:
This thesis is concerned with Maine de Biran’s and Samuel Taylor Coleridge’s conceptions of will, and the way in which both thinkers’ posterities have been affected by the central role of these very conceptions in their respective bodies of thought. The research question that animates this work can therefore be divided into two main parts, one of which deals with will, while the other deals with its effects on posterity. In the first pages of the Introduction, I make the case for a comparison between two philosophers, and show how this comparison can bring one closer to truth, understood not in objective, but in subjective terms. I then justify my choice by underlining that, in spite of their many differences, Maine de Biran and Samuel Taylor Coleridge followed comparable paths, intellectually and spiritually, and came to similar conclusions concerning the essential activity of the human mind. Finally, I ask whether it is possible that this very focus on the human will may have contributed to the state of both thinkers’ works and of the reception of those works. This prologue is followed by five parts. In the first part, the similarities and differences between the two thinkers are explored further. In the second part, the connections between philosophy and singularity are examined, in order to show the ambivalence of the will as a foundation for truth. The third part is dedicated to the traditional division between subject and object in psychology, and its relevance in history and in moral philosophy. The fourth part tackles the complexity of the question of influence, with respect to both Maine de Biran’s and Coleridge’s cases, both thinkers being indebted to many philosophers of all times and places, and having to rely heavily on others for the publication, or the interpretation of their own works. The fifth part is concerned with the different aspects of the faculty of will, and primarily its relationship with interiority, as incommensurability, and actual, conditioned existence in a certain historical and spatial context. It ends with a return to the question of will and posterity and an announcement of what will be covered in the main body of the thesis. The main body is divided into three parts:‘L’émancipation’, ‘L’affirmation, and ‘La projection’. The first part is devoted to the way Maine de Biran and Samuel Taylor Coleridge extricated themselves from one epistemological paradigm to contribute to the foundation of another. It is divided in four chapters. The first chapter deals with the aforementioned change of paradigm, as corresponding to the emergence of two separate but associated movements, Romanticism and what the French philosopher refers to as ‘The Age of History’. The second chapter concerns the movement that preceded them, i.e. the Enlightenment, its main features according to both of our thinkers, and the two epistemological models that prevailed under it and influenced them heavily in their early years: Sensationism (Maine de Biran) and Associationism (Coleridge). The third chapter is about the probable influence of Immanuel Kant and his followers on Maine de Biran and Coleridge, and the various facts that allow us to claim originality for both thinkers’ works. In the fourth chapter, I contrast Maine de Biran and Coleridge with other movements and thinkers of their time, showing that, contrary to their respective thoughts, Maine de Biran and Coleridge could not but break free from the then prevailing systematic approach to truth. The second part of the thesis is concerned with the first part of its research question, namely, Maine de Biran’s and Coleridge’s conceptions of the will. It is divided into four chapters. The first chapter is a reflection on the will as a paradox: on the one hand, the will cannot be caused by any other phenomenon, or it is no longer a will; but it cannot be left purely undetermined, as if it is, it is then not different from chance. It thus needs, in order to be, to be contradictorily already moral. The second chapter is a comparison between Maine de Biran’s and Coleridge’s accounts of the origin of the will, where it is found that the French philosopher only observes that he has a will, whereas the English philosopher postulates the existence of this will. The comparison between Maine de Biran’s and Coleridge’s conceptions of the will is pursued in the third chapter, which tackles the question of the coincidence between the will and the self, in both thinkers’ works. It ends with the fourth chapter, which deals with the question of the relationship between the will and what is other to it, i.e. bodily sensations, passions and desires. The third part of the thesis focuses on the second part of its research question, namely the posterity of Maine de Biran’s and Coleridge’s works. It is divided into four chapters. The first chapter constitutes a continuation of the last chapter of the preceding part, in that that it deals with Maine de Biran’s and Coleridge’s relations to the ‘other’, and particularly their potential and actual audience, and with the way these relations may have affected their writing and publishing practices. The second chapter is a survey of both thinkers’ general reception, where it is found that, while Maine de Biran has been claimed by two important movements of thoughts as their initiator, Coleridge has been neglected by the only real movement he could have, or may indeed have pioneered. The third chapter is more directly concerned with the posterities of Maine de Biran’s and Coleridge’s conceptions of will, and attempts to show that the approach to, and the meaning of the will have evolved throughout the nineteenth century, and in the French Spiritualist and the British Idealist movements, from an essentially personal one to a more impersonal one. The fourth chapter is a partial conclusion, whose aim is to give a precise idea of where Maine de Biran and Coleridge stand, in relation to their century and to the philosophical movements and matters we are concerned with. The conclusion is a recapitulation of what has been found, with a particular emphasis on the dialogue initiated between Maine de Biran and Coleridge on the will, and the relation between will and posterity. It suggests that both thinkers have to pay the price of a problematic reception for the individuality that pervades their respective works, and goes further in suggesting that s/he who chooses to found his individuality on the will is bound to feel this incompleteness in his/her own personal life more acutely than s/he who does not. It ends with a reflection on fixedness and movement, as the two antagonistic states that the theoretician of the will paradoxically aspires to.
Resumo:
Over recent years much has been learned about the way in which depth cues are combined (e.g. Landy et al., 1995). The majority of this work has used subjective measures, a rating scale or a point of subjective equality, to deduce the relative contributions of different cues to perception. We have adopted a very different approach by using two interval forced-choice (2IFC) performance measures and a signal processing framework. We performed summation experiments for depth cue increment thresholds between pairs of pictorial depth cues in displays depicting slanted planar surfaces made from arrays of circular 'contrast' elements. Summation was found to be ideal when size-gradient was paired with contrast-gradient for a wide range of depth-gradient magnitudes in the null stimulus. For a pairing of size-gradient and linear perspective, substantial summation (> 1.5 dB) was found only when the null stimulus had intermediate depth gradients; when flat or steeply inclined surfaces were depicted, summation was diminished or abolished. Summation was also abolished when one of the target cues was (i) not a depth cue, or (ii) added in conflict. We conclude that vision has a depth mechanism for the constructive combination of pictorial depth cues and suggest two generic models of summation to describe the results. Using similar psychophysical methods, Bradshaw and Rogers (1996) revealed a mechanism for the depth cues of motion parallax and binocular disparity. Whether this is the same or a different mechanism from the one reported here awaits elaboration.
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This paper uses a feminist post-structuralist approach to examine the gendered identities of a sample of British business leaders in Britain. While recent national surveys offer many material reasons why women are acutely under-represented as business leaders, the role of language is rarely addressed. This paper explores the ways in which ten senior women and men construct their sense of leadership identities through the medium of interview narratives. Drawing upon two poststructuralist models of analysis (Derrida’s 1987 theory of deconstruction and Bakhtin’s 1927/1981 concept of double-voiced discourse), the paper shows how both females and males are able to shift pragmatically between interwoven corporate discourses, which demand competing cultural allegiances from one moment to the next, allegiances constantly tested by the rapid change and uncertainty that characterise global business. While male leaders experience a relative freedom of movement between different cultural discourses, female leaders are circumscribed by negative and reductive representations of female speech and behaviour. In sum, senior women are required constantly to observe, review, police and repair their use of leadership language, which potentially undermines their confidence and authority as leaders.
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The primary aim of the thesis is to provide a comprehensive investigation of the osmotic dehydration processes in plant tissue. Effort has been concentrated on the modelling for simulating the processes. Two mathematical models for simulating the mass transfer during osmotic dehydration processes in plant tissues are developed and verified using existing experimental data. Both models are based on the mechanism of diffusion and convection of any mobile material that can transport in plant tissues. The mass balance equation for the transport of each constituent is established separately for intracellular and extra-cellular volumes with taking into account the mass transfer across the cell membrane the intracellular and extra-cellular volumes and the shrinkage of the whole tissue. The contribution from turgor pressure is considered in both models. Model two uses Darcy’s law to build the relation between shrinkage velocity and hydrostatic pressure in each volume because the plant tissue can be considered as the porous medium. Moreover, it has been extended to solve the multi-dimensional problems. A lot of efforts have been made to the parameter study and the sensitivity analyses. The parameters investigated including the concentration of the osmotic solution, diffusion coefficient, permeability of the cell membrane, elastic modulus of the cell wall, critical cell volume etc. The models allow us to quantitatively simulate the time evolution of intracellular and extra-cellular volumes as well as the time evolution of concentrations in each cross-section.
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This thesis aims to consider the role played by science in policy making. Firstly, two decision models are considered, synoptic rationality which depends heavily on formal information and comprehensive planning, and disjointed incrementalism, under which decisions are made in a fragmented and remedial manner via the interaction of interested partisans and with little necessity for formal information. Secondly, different descriptions of scientific activity are discussed and a broadly Kuhnian view of science is supported, with what is regarded as a `fact' being heavily influenced by social factors. It is suggested that scientific controversies are more likely to occur in policy related science but for reasons that are intrinsic to science rather than due to some correctable aberration. A number of case studies, including two `in-depth' studies into maternal deprivation and the relationship between hyperactivity and food additives, support this contention and also show that whilst scientific findings can raise issues they cannot aid in the resolution of these as the synoptic model suggests that they should. Instead information supports and legitimates value based policy views, with actual policy decisions arrived at via negotiation and aiming at a balancing of partisan pressures, as suggested by the incremental model. Not only does information not aid the resolution of policy disputes, it cannot do so. When policy is disputed, scientific findings are also likely to be disputed and further research merely attracts more highly destructive criticism. This is termed the over critical model. When policy is decided then there is reduced impetus to critically test scientific ideas; this is termed the under critical model. Both of these situations act to the detriment of science. The main conclusion drawn is that the belief that science is essential to decision making is misleading and may serve to mask rather than illuminate areas of dispute.
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Mental simulations and analogies have been identified as powerful learning tools for RNPs. Furthermore, visuals in advertising have recently been conceptualized as meaningful sources of information as opposed to peripheral cues and thus may help consumers learn about RNPs. The study of visual attention may also contribute to understanding the links between conceptual and perceptual analyses when learning for a RNP. Two conceptual models are developed. the first model consists of causal relationships between the attributes of advertising stimuli for RNPs and consumer responses, as well as mediating influences. The second model focuses on the role of visual attention in product comprehension as a response to advertising stimuli. Two experiments are conducted: a Web-Experiment and an eye-tracking experiment. The first experiment (858 subjects) examines the effect of learning strategies (mental simulation vs. analogy vs. no analogy/no mental simulation) and presentation formats (words vs. pictures) on individual responses. The mediating role of emotions is assessed. The second experiment investigates the effect of learning strategies and presentation formats on product comprehension, along with the role of attention (17 subjects). The findings from experiment 1 indicate that learning strategies and presentation formats can either enhance or undermine the effect of advertising stimuli on individual responses. Moreover, the nature of the product (i.e. hedonic vs. utilitarian vs. hybrid) should be considered when designing communications for RNPs. The mediating role of emotions is verified. Experiment 2 suggests that an increase in attention to the message may either reflect enhanced comprehension or confusion.
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Fluidized bed spray granulators (FBMG) are widely used in the process industry for particle size growth; a desirable feature in many products, such as granulated food and medical tablets. In this paper, the first in a series of four discussing the rate of various microscopic events occurring in FBMG, theoretical analysis coupled with CFD simulations have been used to predict granule–granule and droplet–granule collision time scales. The granule–granule collision time scale was derived from principles of kinetic theory of granular flow (KTGF). For the droplet–granule collisions, two limiting models were derived; one is for the case of fast droplet velocity, where the granule velocity is considerable lower than that of the droplet (ballistic model) and another for the case where the droplet is traveling with a velocity similar to the velocity of the granules. The hydrodynamic parameters used in the solution of the above models were obtained from the CFD predictions for a typical spray fluidized bed system. The granule–granule collision rate within an identified spray zone was found to fall approximately within the range of 10-2–10-3 s, while the droplet–granule collision was found to be much faster, however, slowing rapidly (exponentially) when moving away from the spray nozzle tip. Such information, together with the time scale analysis of droplet solidification and spreading, discussed in part II and III of this study, are useful for probability analysis of the various event occurring during a granulation process, which then lead to be better qualitative and, in part IV, quantitative prediction of the aggregation rate.
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Aims: To assess the effectiveness of a digital-story intervention (short videos made by young people) seeking to reduce the prevalence of young people's binge drinking in Caerphilly. Method: A quasi-experimental design was adopted with three intervention sites and one control site providing the sample (mainly aged 1415 years). Three rounds of self-completion questionnaires, completed prior (T1), immediately after (T2) and 6 months after the intervention (T3). Findings: A total of 1031 questionnaires completed across the three time-points. Two-factor ANOVAs revealed a positive effect on knowledge for the intervention sample. The intervention group results showed stable attitudes towards drinking at the three time-points whilst the control group showed increasing positive attitudes towards drunkenness over the same time period. Intentions towards drunkenness were higher in the control group than the intervention group at T2 (ControlT1 Mean 3.37, T2 Mean 3.90; interventionT1 Mean 3.26, T2 Mean 3.29). Intervention participants got drunk on fewer occasions in the last week (mean occasions last week 1.57) compared to control participants (mean occasions last week 2.00), with the difference approaching statistical significance (F 1.90, p 0.07). Conclusions: Promoting negative attitudes towards drunkenness, alongside a greater sense of control and potential regret about drunkenness are likely to be important factors when considering how to change people's intentions to drink. The study shows the potential to reduce the frequency of drinking behaviour when intentions are changed, and provides recommendations for future interventions of this nature. © 2010 Informa UK Ltd.