Tuning fuzzy power-system stabilizers in multi-machine systems by global optimization algorithms based on efficient domain partitions

In this paper, the problem of global tuning of fuzzy power-system stabilizers (FPSSs) present in a multi-machine power system in order to damp the power system oscillations is considered. In particular, it is formulated as a problem of global minimization of a multiextremal black-box function over a multidimensional hyperinterval. A global optimization technique, recently proposed, is used for solving the stated problem: the search hyperinterval is partitioned into smaller hyperintervals and the objective function is evaluated only at two vertices corresponding to the main diagonal of the generated hyperintervals, thus avoiding unnecessary ponderous simulations. Then, the performances of this technique are numerically compared with ones of a genetic algorithm (GA).     

The value of quality clues in the wine market: evidences from Lazio,Italy

The purpose of the paper is to contribute to understanding the role and effectiveness of different quality clues in the creation of value for the main wines of the Lazio region. The study presents a hedonic price model. An ordinary least squares and a quantile regression models were estimated. The latter is able to detect additional patterns related to the effects of the covariates. Prices are regressed on wine color, sub-regional area of origin, the type of certification of origin, and on experts' evaluation. The analysis is based on data released by three major Italian wine guides: Gambero Rosso, l'Espresso, and AIS (Italian Sommelier Association). Results show that: (i) white and red wines follow two different price patterns; (ii) prices are correlated with experts' evaluation; (iii) the impact of the latter is higher when other quality clues, such as geographical indications, are less effective; (iv) the role of different quality clues varies at different price levels and it is different for red and white wines; overall, wines from the Lazio region are associated with poor to mediocre quality levels. This may explain the decline in reputation and in market share that these wines are experiencing after centuries of popularity.     

MILD combustion in diffusion-controlled regimes of Hot Diluted Fuel

Reactive structures have been characterized in a steady laminar, unidimensional mixing layer on a dense grid of parameters in moderate or intense low-oxygen dilution (MILD) combustion conditions with hot and diluted fuel. The structures have been studied in terms of temperature and heat release profiles in a mixture fraction space for various ranges of stretch rates and for two reference pressures (1 and 10 bar) using a standard code and standard kinetic scheme.In the analysis of reactive structure three synthetic characteristics have been pointed out in previous works as discriminative for the occurrence of different combustion regimes. Such characteristics are the thickness of the oxidation structures, the presence/absence of a pyrolysis region and the correlation/no correlation of the regions of maximum heat release with those at which the mixture is stoichiometric. Following the same criteria, maps of regimes have been built up on a inlet fuel temperature – temperature increase plane for fixed stretch rates and different pressures.It has been pointed out that in diffusion controlled regimes of Hot Diluted Fuel, analysed in this paper, MILD combustion conditions are characterized by flame thickening and pyrolysis depression, which are also typical of flameless combustion. In addition, the region of maximum heat release has a generally high level of correlation with the stoichiometric regions. Thus, MILD combustion regime differs from MILD combustion regime found in other diffusion controlled regimes where the region of maximum heat release is generally not correlated with the stoichiometric regions. In the case presented in this paper, only a second solution, corresponding to a very low conversion occurring in a very wide stretch-rate range, shows no correlation between heat release and stoichiometric mixture fraction. This behavior has been attributed to the oxidative pyrolysis of methane.At atmospheric pressure, the flameless characteristics extend to a low level of preheating, provided that the fuel is diluted, with a consequently low level of temperature increase, thus confirming that MILD and flameless regimes are not coincident in all possible feeding conditions.In general, the results obtained in these Hot-Fuel-Diluted-Fuel conditions are consistent with and extend those reported in the literature for Hot-Oxidant-Diluted-Fuel, Hot-Oxidant and Diluted-Fuel conditions, supporting the assertion that these inlet parameters are a suitable choice for the definition of MILD combustion.     

A strategy for the efficient full-wave description of complex waveguide networks

The mode-matching analysis of rectangular waveguide networks requires a complex segmentation of the structure into simple elements. The way these elements are connected has a strong influence on the computing performance of the code. Moreover, for complex structures the size of the coefficient matrix of the main system can easily reach unaffordable dimensions, so that the use of an efficient solving strategy becomes indispensable. A new approach to the optimum automatic choice of the interconnections is presented, leading to a highly stable and outperforming method of analysis. A Butler 4 × 4 matrix, with six branch guide couplers and four phase shifters, containing 336 uniform waveguide sections and bifurcations, has been studied, and the presented strategy has allowed a performance increase up to two orders of magnitude. © 1996 John Wiley & Sons, Inc.     

An investigation of the numerical properties of the mode-matching technique

A new insight into the numerical properties of the mode-matching (MM) technique is given at the example of capacitive and inductive diaphragms in rectangular waveguide. The presence of two sources of error is pointed out and the existence is demonstrated of an optimum modal ratio which produces the best compensation between the two errors. The MM technique is formulated in a generalized form as an integral equation for either the electric field on the aperture or the current on the diaphragm. This allows the edge condition to be incorporated into the basis functions in order to improve the numerical efficiency of the method. An extensive investigation of the numerical properties of the various formulations in different cases is presented, including the frequency behaviour of the numerical error.     

CD8+ T Cell Senescence: Lights and Shadows in Viral Infections,Autoimmune Disorders and Cancer

CD8⁺ T lymphocytes are a heterogeneous class of cells that play a crucial role in the adaptive immune response against pathogens and cancer. During their lifetime, they acquire cytotoxic functions to ensure the clearance of infected or transformed cells and, in addition, they turn into memory lymphocytes, thus providing a long-term protection. During ageing, the thymic involution causes a reduction of circulating T cells and an enrichment of memory cells, partially explaining the lowering of the response towards novel antigens with implications in vaccine efficacy. Moreover, the persistent stimulation by several antigens throughout life favors the switching of CD8⁺ T cells towards a senescent phenotype contributing to a low-grade inflammation that is a major component of several ageing-related diseases. In genetically predisposed young people, an immunological stress caused by viral infections (e.g., HIV, CMV, SARS-CoV-2), autoimmune disorders or tumor microenvironment (TME) could mimic the ageing status with the consequent acceleration of T cell senescence. This, in turn, exacerbates the inflamed conditions with dramatic effects on the clinical progression of the disease. A better characterization of the phenotype as well as the functions of senescent CD8⁺ T cells can be pivotal to prevent age-related diseases, to improve vaccine strategies and, possibly, immunotherapies in autoimmune diseases and cancer.     

Microwave planar networks: the annular structure

A recent method of analysis that takes into account fringe effects is applied to 2-port annular structures. It is shown that the filtering properties of the structure can be controlled by varying the ring width and/or the position of the ports. Experiments performed on microstrips are in good agreement with the theoretical results.