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Colleen Schinkel, Nadia Stavreva, Pavel Stavrev, Marco Carlone and B. Fallone

Functional form comparison between the population and the individual Poisson based TCP models

In this work, the functional form similarity between the individual and fundamental population TCP models is investigated. Using the fact that both models can be expressed in terms of the geometric parameters γ50 and D50, we show that they have almost identical functional form for values of γ50 ≥ 1. The conceptual inadequacy of applying an individual model to clinical data is also discussed. A general individual response TCP expression is given, parameterized by Df and γf - the dose corresponding to a control level of f, and the normalized slope at that point. It is shown that the dose-response may be interpreted as an individual response only if γ50 is sufficiently high. Based on the functional form equivalency between the individual and the population TCP models, we discuss the possibility of applying the individual TCP model for the case of heterogeneous irradiations. Due to the fact that the fundamental population TCP model is derived for homogeneous irradiations only, we propose the use of the EUD, given by the generalized mean dose, when the fundamental population TCP model is used to fit clinical data.

Open access

Magdalena Ulrichs

Abstract

Dynamic macroeconomic models (both VAR and DSGE) currently play a very significant role in macroeconomic modelling. But these types of models rarely take into account the impact of financial markets on the behaviour of economies, they are rather more focused on the monetary transmission mechanism. The financial crisis of 2007-2008 highlighted the impact of the financial market on the macroeconomy. In this context macroprudential policy and financial stability analysis has gained a stronger meaning. The main aim of the paper is to estimate a model that simultaneously explains the dynamics of macroeconomic and financial variables and to assess whether the identified relationships are stable over time. Therefore, based on the estimated empirical structural vector autoregression model explaining the interactions between the real economy, the financial system and monetary policy in Poland, financial and macroeconomic shocks were identified. It was shown that the impulse reaction functions changed after the financial crisis. On the basis of Markov‑ Switching vector autoregression model probabilities of transitions between states of the economy and the regime-dependent impulse reaction functions were estimated.

Open access

Harald J. van Heerde, Shuba Srinivasan and Marnik G. Dekimpe

Abstract

To evaluate the success of a new product, managers need to determine how much of its new demand is due to cannibalizing the company’s other products, rather than drawing from competition or generating primary demand. A new model allows managers to estimate cannibalization effects and to calculate the new product’s net demand, which may be considerably less than its total demand. The new methodology is applied to the introduction of the Lexus RX 300 using detailed car transaction data. This case is especially interesting since the Lexus RX 300 was the first crossover SUV, implying that its demand could come from both the SUV and the Luxury Sedan categories. As Lexus was active in both categories, there was a double cannibalization potential. Indeed, demand is shown to originate from different sources and to vary over time. The results contain valuable insights for evaluating and managing brand extensions.

Open access

Piotr Płuciennik

Abstract

Subprime crisis which started in the USA in 2007 was the cause of the most significant economic disturbances since the Great Depression in 1930s. Soon it transmitted to other countries, including those in which banks were not engaged in the subprime mortgage market. The crisis hit various sectors of national economies and led to changing of the trends on the stock markets, which are connected to American capital market. In the following article we researched the influence of the American market on the other markets in the context of the financial crisis. Our analysis is based on the results obtained from the multivariate parametric models. Seeing that the data space is high-dimensional, we used GO-GARCH models introduced by van der Weide (2005) and Boswijk and van der Weide (2006).

Open access

Justyna Brzezińska

Abstract

Item Response Theory (IRT) is a modern statistical method using latent variables designed to model the interaction between a subject’s ability and the item level stimuli (difficulty, guessing). Item responses are treated as the outcome (dependent) variables, and the examinee’s ability and the items’ characteristics are the latent predictor (independent) variables. IRT models the relationship between a respondent’s trait (ability, attitude) and the pattern of item responses. Thus, the estimation of individual latent traits can differ even for two individuals with the same total scores. IRT scores can yield additional benefits and this will be discussed in detail. In this paper theory and application with R software with the use of packages designed for modelling IRT will be presented.

Open access

A.A. Markou and G.D. Manolis

Abstract

Numerical methods for the solution of dynamical problems in engineering go back to 1950. The most famous and widely-used time stepping algorithm was developed by Newmark in 1959. In the present study, for the first time, the Newmark algorithm is developed for the case of the trilinear hysteretic model, a model that was used to describe the shear behaviour of high damping rubber bearings. This model is calibrated against free-vibration field tests implemented on a hybrid base isolated building, namely the Solarino project in Italy, as well as against laboratory experiments. A single-degree-of-freedom system is used to describe the behaviour of a low-rise building isolated with a hybrid system comprising high damping rubber bearings and low friction sliding bearings. The behaviour of the high damping rubber bearings is simulated by the trilinear hysteretic model, while the description of the behaviour of the low friction sliding bearings is modeled by a linear Coulomb friction model. In order to prove the effectiveness of the numerical method we compare the analytically solved trilinear hysteretic model calibrated from free-vibration field tests (Solarino project) against the same model solved with the Newmark method with Netwon-Raphson iteration. Almost perfect agreement is observed between the semi-analytical solution and the fully numerical solution with Newmark’s time integration algorithm. This will allow for extension of the trilinear mechanical models to bidirectional horizontal motion, to time-varying vertical loads, to multi-degree-of-freedom-systems, as well to generalized models connected in parallel, where only numerical solutions are possible.