864 resultados para Rasch modelling, structural equation modelling, experimental design


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Purpose – This study proposes to use the Theory of Planned Behaviour to predict entrepreneurial intentions among students in five developing and nine developed countries. The purpose is to investigate whether entrepreneurial intention and its antecedents differ between developing and developed countries, and to test the theory in the two groups of countries. Design/methodology/approach – A total of 2,225 students in 13 countries participated in this study by responding to a structured questionnaire in classrooms. Structural equation modelling was used to analyse the data. Findings – The findings indicate that respondents from developing countries have stronger entrepreneurial intentions than those from developed countries. Moreover, the respondents from developing countries also score higher on the theory's antecedents of entrepreneurial intentions – attitudes, subjective norms, and perceived behavioural control – than respondents from developed countries. The findings support the Theory of Planned Behaviour in both developing and developed countries. Research limitations/implications – The findings strongly support the Theory of Planned Behaviour. The measure of subjective norms used, a multiple-item index encompassing the views of other people and motivation to comply with these, seems to have advantages over other measures of this concept. Practical implications – Developing countries need to focus on the development of institutions that can support entrepreneurial efforts. At the same time, developed economies may need to accept that entrepreneurial intentions are dependent on the dynamism of an economic environment and possibly on risk-perceiving behaviours. Originality/value – While multiple-country studies on entrepreneurship in developing and developed countries have been called for, no previous study has compared entrepreneurial intentions between developing and developed countries. The inclusion of developing countries provides a unique quasi-experimental setting in which to test the theory.

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Problema. Esta investigación se aproxima al entorno escolar con el propósito de avanzar en la comprensión de los imaginarios de los adolescentes y docentes en torno al cuerpo, la corporalidad y la AF, como un elemento relevante en el diseño de programas y planes efectivos para fomento de la práctica de AF. Objetivo. Analizar los imaginarios sociales de docentes y adolescentes en torno a los conceptos de cuerpo, corporalidad y AF. Métodos. Investigación de corte cualitativo, descriptivo e interpretativo. Se realizaron entrevistas semi-estructuradas a docentes y a estudiantes entre los 12 y 18 años de un colegio público de Bogotá. Se realizó análisis de contenido. Se compararon los resultados de estudiantes por grupos de edades y género. Resultados. Docentes y estudiantes definen el cuerpo a partir de las características biológicas, las diferencias sexuales y las funciones vitales. La definición de corporalidad en los estudiantes se encuentra ligada con la imagen y la apariencia física; los docentes la entienden como la posibilidad de interactuar con el entorno y como la materialización de la existencia. La AF en los estudiantes se asocia con la práctica de ejercicio y deporte, en los docentes se comprende como una práctica de autocuidado que permite el mantenimiento de la salud. Conclusiones. Para promover la AF tempranamente como una experiencia vital es necesario intervenir los espacios escolares. Hay que vincular al cuerpo a los procesos formativos con el propósito de desarrollar la autonomía corporal, este aspecto implica cambios en los currículos.

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Purpose – The current study aims to study Hospital volunteers’ intention to stay in an organization through understanding motivation, management factors and satisfaction. Design/methodology/approach – A total of 304 Hospital volunteers, mainly women, completed a questionnaire measuring motivations, management factors, satisfaction and intention to stay. In this study structural equation modelling was used. Findings – Results demonstrate that there is a positive relationship between (a) motivation and satisfaction, (b) management factors and satisfaction, (c) satisfaction and intention to stay and (d) motivation and management factors. These results present important outcomes that should be reflected in the way organizations operate. Research limitations/implications – This research was restricted to a health care context and to the opinion of only one stakeholder (volunteers). We assume volunteer intent to stay is a main predictor of retention. However, there are other variables not considered here that might influence intent to stay. Practical implications – This research indicates aspects which are most valued by volunteers and allows NPOs to design and establish appropriate and assertive management policies. Originality/value – The value of this paper is that it looks at understanding what factors influence volunteers’ intention to stay.

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This work presents recent results concerning a design methodology used to estimate the positioning deviation for a gantry (Cartesian) manipulator, related mainly to structural elastic deformation of components during operational conditions. The case-study manipulator is classified as gantry type and its basic dimensions are 1,53m x 0,97m x 1,38m. The dimensions used for the calculation of effective workspace due to end-effector path displacement are: 1m x 0,5m x 0,5m. The manipulator is composed by four basic modules defined as module X, module Y, module Z and terminal arm, where is connected the end-effector. Each module controlled axis performs a linear-parabolic positioning movement. The planning path algorithm has the maximum velocity and the total distance as input parameters for a given task. The acceleration and deceleration times are the same. Denavit-Hartemberg parameterization method is used in the manipulator kinematics model. The gantry manipulator can be modeled as four rigid bodies with three degrees-of-freedom in translational movements, connected as an open kinematics chain. Dynamic analysis were performed considering inertial parameters specification such as component mass, inertia and center of gravity position of each module. These parameters are essential for a correct manipulator dynamic modelling, due to multiple possibilities of motion and manipulation of objects with different masses. The dynamic analysis consists of a mathematical modelling of the static and dynamic interactions among the modules. The computation of the structural deformations uses the finite element method (FEM).

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Este estudio mide el efecto del uso del Internet en el crecimiento de pequeñas y medianas empresas (PYMES) en el contexto empresarial de una economía emergente. Se revisan estudios empíricos sobre el uso de Internet en PYMES y se describen factores que pueden tener una influencia en el uso del Internet y de su efecto en el crecimiento. Con una muestra de PYMES en México se contrasta el modelo de investigación usando ecuaciones estructurales. El efecto total del uso del Internet en el crecimiento de la muestra se considera plausible, con un porcentaje de varianza que explica el crecimiento en un 47%. El estudio sugiere algunas implicaciones para la teoría y para la gestión.

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This paper investigates Willingness to Accept (WTA) Genetic Modification (GM) foods based on experimental auctions carried out in the USA, UK and France. It explores perceptions of risk and benefits, moral concerns and their antecedents, attitudes to the environment and technology and trust in various sources using Structural Equation Modelling (SEM). Trust in information provided by industry proved to be the most important determinant of risk/benefit perceptions and WTA followed by general attitudes to the environment and technology. Education and age are also enhance perceived benefits and lower perceived risks of GM. Perception of risk/benefit and moral concerns all have significant effects on consumers' WTA but the perceived benefits are most important. The research suggests that trust-building by industry would be the most effective in enhancing GM acceptance.

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A common problem in many data based modelling algorithms such as associative memory networks is the problem of the curse of dimensionality. In this paper, a new two-stage neurofuzzy system design and construction algorithm (NeuDeC) for nonlinear dynamical processes is introduced to effectively tackle this problem. A new simple preprocessing method is initially derived and applied to reduce the rule base, followed by a fine model detection process based on the reduced rule set by using forward orthogonal least squares model structure detection. In both stages, new A-optimality experimental design-based criteria we used. In the preprocessing stage, a lower bound of the A-optimality design criterion is derived and applied as a subset selection metric, but in the later stage, the A-optimality design criterion is incorporated into a new composite cost function that minimises model prediction error as well as penalises the model parameter variance. The utilisation of NeuDeC leads to unbiased model parameters with low parameter variance and the additional benefit of a parsimonious model structure. Numerical examples are included to demonstrate the effectiveness of this new modelling approach for high dimensional inputs.

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The problem of technology obsolescence in information intensive businesses (software and hardware no longer being supported and replaced by improved and different solutions) and a cost constrained market can severely increase costs and operational, and ultimately reputation risk. Although many businesses recognise technological obsolescence, the pervasive nature of technology often means they have little information to identify the risk and location of pending obsolescence and little money to apply to the solution. This paper presents a low cost structured method to identify obsolete software and the risk of their obsolescence where the structure of a business and its supporting IT resources can be captured, modelled, analysed and the risk to the business of technology obsolescence identified to enable remedial action using qualified obsolescence information. The technique is based on a structured modelling approach using enterprise architecture models and a heatmap algorithm to highlight high risk obsolescent elements. The method has been tested and applied in practice in two consulting studies carried out by Capgemini involving three UK police forces. However the generic technique could be applied to any industry based on plans to improve it using ontology framework methods. This paper contains details of enterprise architecture meta-models and related modelling.

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We apply a new parameterisation of the Greenland ice sheet (GrIS) feedback between surface mass balance (SMB: the sum of surface accumulation and surface ablation) and surface elevation in the MAR regional climate model (Edwards et al., 2014) to projections of future climate change using five ice sheet models (ISMs). The MAR (Modèle Atmosphérique Régional: Fettweis, 2007) climate projections are for 2000–2199, forced by the ECHAM5 and HadCM3 global climate models (GCMs) under the SRES A1B emissions scenario. The additional sea level contribution due to the SMB– elevation feedback averaged over five ISM projections for ECHAM5 and three for HadCM3 is 4.3% (best estimate; 95% credibility interval 1.8–6.9 %) at 2100, and 9.6% (best estimate; 95% credibility interval 3.6–16.0 %) at 2200. In all results the elevation feedback is significantly positive, amplifying the GrIS sea level contribution relative to the MAR projections in which the ice sheet topography is fixed: the lower bounds of our 95% credibility intervals (CIs) for sea level contributions are larger than the “no feedback” case for all ISMs and GCMs. Our method is novel in sea level projections because we propagate three types of modelling uncertainty – GCM and ISM structural uncertainties, and elevation feedback parameterisation uncertainty – along the causal chain, from SRES scenario to sea level, within a coherent experimental design and statistical framework. The relative contributions to uncertainty depend on the timescale of interest. At 2100, the GCM uncertainty is largest, but by 2200 both the ISM and parameterisation uncertainties are larger. We also perform a perturbed parameter ensemble with one ISM to estimate the shape of the projected sea level probability distribution; our results indicate that the probability density is slightly skewed towards higher sea level contributions.

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Purpose – Corporate Occupiers require offices and services which meet their business needs, whilst landlords must attract and retain occupiers in order to maximise occupancy and rental income. The purpose of this research is to help landlords and corporate occupiers understand each other better, in order to achieve a mutually beneficial relationship. Design/methodology/approach - This paper analyses interviews with 1334 office tenants in the UK, conducted over an 11-year period, to investigate determinants of occupier satisfaction, loyalty and advocacy. Structural equation modelling and regressions are performed using respondents’ ratings of satisfaction with many aspects of occupancy as explanatory variables. The dependent variables include satisfaction with property management, value for money, overall occupier satisfaction, lease renewal intentions and occupiers’ willingness to recommend their landlord. Findings - The aspects with most impact on occupiers’ satisfaction are the office building itself, its location and amenities, and also communication with their property manager, a belief that their business needs are understood and the property manager’s responsiveness to occupiers’ requests. Occupiers’ loyalty depends mainly upon feeling that their rent and service charges provide value for money, an amicable leasing process, the professionalism of their property manager and the Corporate Social Responsibility of the Landlord. ‘Empathy’ is crucial to occupiers’ willingness to recommend their landlord, and clear documentation and efficient legal process improve occupiers’ perception of receiving ‘Value for Money’. Research Limitations - The sample is skewed towards occupiers of prime office buildings in the UK, owned by landlords who care sufficiently about their tenants to commission studies into occupier satisfaction. Practical implications - This research should help to improve the landlord – tenant relationship, benefitting the businesses that rent property and helping building managers understand where to focus their efforts to achieve maximum effect on occupier satisfaction, loyalty and advocacy. Originality/value - There has been little academic research into the determinants of satisfaction of occupiers of UK commercial property. This large-scale study enables the most influential factors to be identified and prioritised.

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In this paper we study the behavior of a structure vulnerable to excessive vibrations caused by an non-ideal power source. To perform this study, the mathematical model is proposed, derive the equations of motion for a simple plane frame excited by an unbalanced rotating machine with limited power (non-ideal motor). The non-linear and non-ideal dynamics in system is demonstrated with a chaotic behavior. We use a State-Dependent Riccati Equation Control technique for regulate the chaotic behavior, in order to obtain a periodic orbit small and to decrease its amplitude. The simulation results show the identification by State-Dependent Riccati Equation Control is very effective. © 2013 Academic Publications, Ltd.

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Besnoitia besnoiti is an apicomplexan parasite responsible for bovine besnoitiosis, a disease with a high prevalence in tropical and subtropical regions and re-emerging in Europe. Despite the great economical losses associated with besnoitiosis, this disease has been underestimated and poorly studied, and neither an effective therapy nor an efficacious vaccine is available. Protein disulfide isomerase (PDI) is an essential enzyme for the acquisition of the correct three-dimensional structure of proteins. Current evidence suggests that in Neosporacaninum and Toxoplasmagondii, which are closely related to B. besnoiti, PDI play an important role in host cell invasion, is a relevant target for the host immune response, and represents a promising drug target and/or vaccine candidate. In this work, we present the nucleotide sequence of the B. besnoiti PDI gene. BbPDI belongs to the thioredoxin-like superfamily (cluster 00388) and is included in the PDI_a family (cluster defined cd02961) and the PDI_a_PDI_a'_c subfamily (cd02995). A 3D theoretical model was built by comparative homology using Swiss-Model server, using as a template the crystallographic deduced model of Tapasin-ERp57 (PDB code 3F8U chain C). Analysis of the phylogenetic tree for PDI within the phylum apicomplexa reinforces the close relationship among B. besnoiti, N. caninum and T. gondii. When subjected to a PDI-assay based on the polymerisation of reduced insulin, recombinant BbPDI expressed in E. coli exhibited enzymatic activity, which was inhibited by bacitracin. Antiserum directed against recombinant BbPDI reacted with PDI in Western blots and by immunofluorescence with B. besnoiti tachyzoites and bradyzoites.

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OBJECTIVES: The purpose of the present study was to investigate predictors of perceived vulnerability for breast cancer in women with an average risk for breast cancer. On the basis of empirical findings that suggested which variables might be associated with perceived vulnerability for breast cancer, we investigated whether knowledge of breast cancer risk factors, cancer worry, intrusions about breast cancer, optimism about not getting cancer and perceived health status have a predictive value for perceived breast cancer vulnerability. DESIGN: In a 3-step approach, we recruited 292 women from the general public in Germany who had neither a family history of breast cancer nor breast cancer themselves. After receiving an initial informational letter about study objectives, the women were interviewed by telephone and then asked to fill in a self-administered questionnaire. METHODS: We used structural equation modelling and hypothesized that each of the included variables has a direct influence on perceived vulnerability for breast cancer. RESULTS: We found a valid model with acceptable fit indices. Optimism about not getting cancer, intrusions about breast cancer and women's perceived health status explained 32% of the variance of perceived vulnerability for breast cancer. Cancer worry and knowledge about breast cancer did not influence perceived vulnerability for breast cancer. CONCLUSION: Perceived vulnerability for breast cancer is associated with health-related variables more than with knowledge about breast cancer risk factors.

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Introduction Prospective memory (PM), the ability to remember to perform intended activities in the future (Kliegel & Jäger, 2007), is crucial to succeed in everyday life. PM seems to improve gradually over the childhood years (Zimmermann & Meier, 2006), but yet little is known about PM competences in young school children in general, and even less is known about factors influencing its development. Currently, a number of studies suggest that executive functions (EF) are potentially influencing processes (Ford, Driscoll, Shum & Macaulay, 2012; Mahy & Moses, 2011). Additionally, metacognitive processes (MC: monitoring and control) are assumed to be involved while optimizing one’s performance (Krebs & Roebers, 2010; 2012; Roebers, Schmid, & Roderer, 2009). Yet, the relations between PM, EF and MC remain relatively unspecified. We intend to empirically examine the structural relations between these constructs. Method A cross-sectional study including 119 2nd graders (mage = 95.03, sdage = 4.82) will be presented. Participants (n = 68 girls) completed three EF tasks (stroop, updating, shifting), a computerised event-based PM task and a MC spelling task. The latent variables PM, EF and MC that were represented by manifest variables deriving from the conducted tasks, were interrelated by structural equation modelling. Results Analyses revealed clear associations between the three cognitive constructs PM, EF and MC (rpm-EF = .45, rpm-MC = .23, ref-MC = .20). A three factor model, as opposed to one or two factor models, appeared to fit excellently to the data (chi2(17, 119) = 18.86, p = .34, remsea = .030, cfi = .990, tli = .978). Discussion The results indicate that already in young elementary school children, PM, EF and MC are empirically well distinguishable, but nevertheless substantially interrelated. PM and EF seem to share a substantial amount of variance while for MC, more unique processes may be assumed.

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Low parental monitoring is related to youth risk behaviors such as delinquency and aggression. The purpose of this dissertation was to describe the development and evaluation of a parent education intervention to increase parental monitoring in Hispanic parents of middle school children.^ The first study described the process of intervention mapping as used to develop Padres Trabajando por la Paz, a newsletter intervention for parents. Using theory, empirical literature, and information from the target population, performance objectives and determinants for monitoring were defined. Learning objectives were specified and a staged social-cognitive approach was used to develop methods and strategies delivered through newsletters.^ The second study examined the outcomes of a randomized trial of the newsletter intervention. Outcome measures consisted of a general measure of monitoring, parent and child reports of monitoring behaviors targeted by the intervention, and psychosocial determinants of monitoring (self-efficacy, norms, outcome expectancies, knowledge, and beliefs). Seventy-seven parents completed the randomized trial, half of which received four newsletters over an eight-week period. Results revealed a significant interaction effect for baseline and treatment for parent's reports of norms for monitoring (p =.009). Parents in the experimental condition who scored low at baseline reported increased norms for monitoring at follow-up. A significant interaction effect for child reports of parental monitoring behaviors (p =.04) reflected an small increase across baseline levels in the experimental condition and decreases for the control condition at higher baseline scores. Both groups of parents reported increased levels of monitoring at follow-up. No other outcome measures varied significantly by condition.^ The third study examined the relationship between the psychosocial determinants of parental monitoring and parental monitoring behaviors in the study population. Weak evidence for a relationship between outcome expectancies and parental monitoring behaviors suggests further research in the area utilizing stronger empirical models such as longitudinal design and structural equation modeling.^ The low-cost, minimal newsletter intervention showed promise for changing norms among Hispanic parents for parental monitoring. In light of the importance of parental monitoring as a protective factor for youth health risk behaviors, more research needs to be done to develop and evaluate interventions to increase parental monitoring. ^