921 research outputs found
Linear parameter-varying model to design control laws for an artificial pancreas
The contribution of this work is the generation of a control-oriented model for insulin-glucose dynamic regulation in type 1 diabetes mellitus (T1DM). The novelty of this model is that it includes the time-varying nature, and the inter-patient variability of the glucose-control problem. In addition, the model is well suited for well-known and standard controller synthesis procedures. The outcome is an average linear parameter-varying (LPV) model that captures the dynamics from the insulin delivery input to the glucose concentration output constructed based on the UVA/Padova metabolic simulator. Finally, a system-oriented reinterpretation of the classical ad-hoc 1800 rule is applied to adapt the model's gain. The effectiveness of this approach is quantified both in open- and closed-loop. The first one by computing the root mean square error (RMSE) between the glucose deviation predicted by the proposed model and the UVA/Padova one. The second measure is determined by using the ν-gap as a metric to determine distance, in terms of closed-loop performance, between both models. For comparison purposes, both open- (RMSE) and closed-loop (ν-gap metric) quality indicators are also computed for other control-oriented models previously presented. This model allows the design of LPV controllers in a straightforward way, considering its affine dependence on the time-varying parameter, which can be computed in real-time. Illustrative simulations are included. In addition, the presented modeling strategy was employed in the design of an artificial pancreas (AP) control law that successfully withstood rigorous testing using the UVA/Padova simulator, and that was subsequently deployed in a clinical trial campaign where five adults remained in closed-loop for 36 h. This was the first ever fully closed-loop clinical AP trial in Argentina, and the modeling strategy presented here is considered instrumental in resulting in a very successful clinical outcome.Fil: Colmegna, Patricio Hernán. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Sánchez Peña, Ricardo S.. Instituto TecnolĂłgico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Gondhalekar, R.. Harvard University; Estados Unido
Are all Credit Default Swap databases equal?
The presence of different prices in different databases for the same securities can impair the comparability of research efforts and seriously damage the management decisions based upon such research. In this study we compare the six major sources of corporate Credit Default Swap prices: GFI, Fenics, Reuters EOD, CMA, Markit and JP Morgan, using the most liquid single name 5-year CDS of the components of the leading market indexes, iTraxx (European firms) and CDX (US firms) for the period from 2004 to 2010. We find systematic differences between the data sets implying that deviations from the common trend among prices in the different databases are not purely random but are explained by idiosyncratic factors as well as liquidity, global risk and other trading factors. The lower is the amount of transaction prices available the higher is the deviation among databases. Our results suggest that the CMA database quotes lead the price discovery process in comparison with the quotes provided by other databases. Several robustness tests confirm these results.Credit Default Swap prices, Databases, Liquidity
Interpolation for gain-scheduled control with guarantees
Here, a methodology is presented which considers the interpolation of linear time-invariant (LTI) controllers designed for different operating points of a nonlinear system in order to produce a gain-scheduled controller. Guarantees of closed-loop quadratic stability and performance at intermediate interpolation points are presented in terms of a set of linear matrix inequalities (LMIs). The proposed interpolation scheme can be applied in cases where the system must remain at the operating points most of the time and the transitions from one point to another rarely occur, e.g., chemical processes, satellites.Fil: Bianchi, Fernando Daniel. Instituto TecnolĂłgico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Sánchez Peña, Ricardo S.. Instituto TecnolĂłgico de Buenos Aires; Argentin
High-performance functional renormalization group calculations for interacting fermions
We derive a novel computational scheme for functional Renormalization Group
(fRG) calculations for interacting fermions on 2D lattices. The scheme is based
on the exchange parametrization fRG for the two-fermion interaction, with
additional insertions of truncated partitions of unity. These insertions
decouple the fermionic propagators from the exchange propagators and lead to a
separation of the underlying equations. We demonstrate that this separation is
numerically advantageous and may pave the way for refined, large-scale
computational investigations even in the case of complex multiband systems.
Furthermore, on the basis of speedup data gained from our implementation, it is
shown that this new variant facilitates efficient calculations on a large
number of multi-core CPUs. We apply the scheme to the , Hubbard model on
a square lattice to analyze the convergence of the results with the bond length
of the truncation of the partition of unity. In most parameter areas, a fast
convergence can be observed. Finally, we compare to previous results in order
to relate our approach to other fRG studies.Comment: 26 pages, 9 figure
Are all credit default swap databases equal?
The presence of different prices in different databases for the same securities can impair the comparability
of research efforts and seriously damage the management decisions based upon such research. In this
study we compare the six major sources of corporate Credit Default Swap prices: GFI, Fenics, Reuters
EOD, CMA, Markit and JP Morgan, using the most liquid single name 5-year CDS of the components
of the leading market indexes, iTraxx (European firms) and CDX (US firms) for the period from 2004
to 2010. We find systematic differences between the data sets implying that deviations from the common
trend among prices in the different databases are not purely random but are explained by idiosyncratic
factors as well as liquidity, global risk and other trading factors. The lower is the amount of transaction
prices available the higher is the deviation among databases. Our results suggest that the CMA database
quotes lead the price discovery process in comparison with the quotes provided by other databases.
Several robustness tests confirm these results
Towards a common European monetary union risk free rate
A common European bond would yield a common European Monetary Union risk free rate. We present
tentative estimates of this common risk free for the European Monetary Union countries from 2004
to 2009 using variables motivated by a theoretical portfolio selection model. First, we analyze the
determinants of EMU sovereign yield spreads and find significant effects of the credit quality, macro,
correlation, and liquidity variables. However, their effects are different before and after the current
financial crisis, being stronger in the latter period. Robustness tests with different data frequencies,
benchmarks, liquidity variables, cross section regressions and balanced panels confirm the initial results.
We propose four different estimates of the common risk free rate and show that, in most cases, this
common rate could imply savings in borrowing costs for all the countries involved
Assessment of hormonal parameters in long-term karate Practitioners
Introduction: Karate is a Japanese martial art which is widely practiced in the Western world as a form of self-defense, as well as a discipline to achieve physical and mental balance.However, little is known with respect to its specific psychobiological effects, particularly in relation to the influence that karate may exert on the endocrine system. Thus, in the present study we analyzed the effects of regular karate practice on several hormonal parameters.
Methods: 27 healthy volunteer subjects participated in the study, of whom 15 were allocated to the experimental group, and 12 were assigned to the control group. Experimental
subjects were karate players with a minimum of 3 years of practice in this discipline. Blood samples for the quantification of hormonal parameters (TSH, T3, T4, PTH, ACTH, cortisol, and DHEA) were taken in both groups. To compare the means of the control and experimental group, a t-test for independent groups was performed in each dependent variable.
Results: Significant differences between the experimental and control group were found in T3, T4, and cortisol, with karate players showing lower blood levels of these hormones than
control.
Conclusions: These findings reveal that long-term karate practice is associated to a significant endocrine modulation, which suggests interesting psychobiological implications,
and lends itself to potential clinical considerations. Further research is needed to properly assess the scope of the peculiar hormonal profile displayed by advanced karate practitioners.Universidad de Málaga, Campus de Excelencia Internacional AndalucĂa Tec
Immune modulation after long-term karate practice
Introduction: Karate is a Japanese martial arts system which traces its roots back to China, and is nowadays widely popular both as a method of self-defense, as well as a discipline
with potential physical and psychological benefits. However, karate has been scarcely investigated from a psychobiological perspective, and its effects on the immune system remain virtually unknown. Therefore, we designed the present study with the aim of analyzing the effects of several years of regular karate practice on different immune parameters.
Methods: 27 healthy volunteer subjects participated in the study, 15 being allocated to the experimental group, and 12 to the control group. Experimental subjects were all karate players who had practiced this martial art for a minimum of three years. Blood samples for the quantification of immune parameters (leukocytes, neutrophils, monocytes, eosinophils, basophils, lymphocytes, IgG, IgA, IgM, IgE) were taken in both groups. As statistical analysis, a t-test for independent groups was performed in each dependent variable.
Results: Compared to the control group, karate practitioners exhibited a significantly higher number of leukocytes, monocytes, and lymphocytes, as well as greater serum concentrations of IgG and IgM.
Conclusions: Our findings show that long-term karate practice is related to a broad modulation of immune parameters, including leukocytes counts as well as immunoglobulin
concentrations. This peculiar immunomodulatory profile, apart from its psychobiological relevance, may have noteworthy clinical implications. Further investigation would be necessary to fully elucidate the influence that long-term karate training can exert on the immune system.Universidad de Málaga, Campus de Excelencia Internacional AndalucĂa Tec
A gain-scheduled LPV control for oxygen stoichiometry regulation in PEM fuel cell systems
The article addresses the LPV control of a Polymer Electrolyte Membrane Fuel Cell (PEMFC). In order to optimize efficiency, PEMFCs require reliable control systems ensuring stability and performance, as well as robustness to model uncertainties
and external perturbations. On the other hand, PEMFCs present a highly nonlinear behavior that demands nonlinear and/or adaptive control strategies to achieve high performance in the entire operating range. Here, a linear parameter varying (LPV) gain scheduled control is proposed. The control is based on a piecewise affine LPV representation of the PEMFC, a model that can be available in practice. In order to deal with the saturation of the control action, an LPV anti-windup compensation is also proposed. The complete control strategy is applied to several experimental practical situations in a laboratory fuel cell system to evaluate its performance and the reliability of the proposed algorithms.The research of F.D. Bianchi was supported by the European Regional Development Funds (ERDF, FEDER Programa Competitivitat de Catalunya 2007-2013). The research of C. Kunusch has been supported by the Seventh Framework Programme of the European Community through the Marie Curie actions (GA: PCIG09-GA-2011-293876) and project Puma-Mind (GA: FCH-JU-2011-1-303419), as well as by the CICYT project DPI2011-25649 (MICINN-Spain). The research of C. Ocampo-Martinez has been supported by the project MACPERCON (Ref. 201250E027) of the CSIC. The research of R.S. Sánchez Peña has been supported by CONICET and
grant PICT2008-290 from the PRH Program of the Ministry of Science, Technology and Innovation of Argentina.Peer Reviewe
Strategic planning for community sustainability in model forests: Case study of the Yoro model forest, Honduras
El estudio plantea una planificaciĂłn estratĂ©gica de desarrollo en los Bosques Modelo a partir del estudio del caso del Bosque Modelo de Yoro, en Honduras, en donde el sector de la industria maderera y en concreto el subsector de carpinterĂa y mueble, parece tener más ventajas competitivas para producir productos de exportaciĂłn que generen riqueza en la zona, dada la escasa capacidad de compra de la regiĂłn. A este subsector se le realiza un Análisis estratĂ©gico, una ElecciĂłn estratĂ©gica y una ImplementaciĂłn estratĂ©gica determinando que el desarrollo del subsector podrĂa pasar por crear una cooperativa capaz de suministrar partes de muebles a una empresa de carácter internacional que tenga como estrategia comercial la venta de muebles naturales, ecolĂłgicos y que estĂ© comprometida socialment
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