Relative cluster entropy for power-law correlated sequences

We propose an information-theoretical measure, the \textit{relative cluster entropy} $\mathcal{D_{C}}[P \| Q]$, to discriminate among cluster partitions characterised by probability distribution functions $P$ and $Q$. The measure is illustrated with the clusters generated by pairs of fractional Brownian motions with Hurst exponents $H_1$ and $H_2$ respectively. For subdiffusive, normal and superdiffusive sequences, the relative entropy sensibly depends on the difference between $H_1$ and $H_2$. By using the \textit{minimum relative entropy} principle, cluster sequences characterized by different correlation degrees are distinguished and the optimal Hurst exponent is selected. As a case study, real-world cluster partitions of market price series are compared to those obtained from fully uncorrelated sequences (simple Browniam motions) assumed as a model. The \textit{minimum relative cluster entropy} yields optimal Hurst exponents $H_1=0.55$, $H_1=0.57$, and $H_1=0.63$ respectively for the prices of DJIA, S\&P500, NASDAQ: a clear indication of non-markovianity. Finally, we derive the analytical expression of the relative cluster entropy and the outcomes are discussed for arbitrary pairs of power-laws probability distribution functions of continuous random variables

A novel correlation model for horizontal axis wind turbines operating at high-interference flow regimes

Driven by economics-of-scale factors, wind-turbine rotor sizes have increased formidably in recent years. Larger rotors with lighter blades of increased flexibility will experiment substantially higher levels of deformation. Future turbines will also incorporate advanced control strategies to widen the range of wind velocities over which energy is captured. These factors will extend turbine operational regimes, including flow states with high interference factors. In this paper we derive a new empirical relation to both improve and extend the range of Blade Element Momentum (BEM) models, when applied to high interference-factor regimes. In most BEM models, these flow regimes are modeled using empirical relations derived from experimental data. However, an empirical relation that best represents these flow states is still missing. The new relation presented in this paper is based on data from numerical experiments performed on an actuator disk model, and implemented in the context of a novel model of the BEM family called the DRD-BEM (Dynamic Rotor Deformation—BEM), recently introduced in Ponta, et al., 2016. A detailed description of the numerical experiments is presented, followed by DRD-BEM simulation results for the case of the benchmark NREL-5MW Reference Wind Turbine with this new polynomial curve incorporated

The role of monetary incentives: Bonus and/or stimulus

In this paper, the role of the monetary incentives in the employee performance is investigated in the context of Public Administration (PA). In particular, the distribution of monetary incentives among the employees based on the position held, is compared with a merit approach which tends to recognize and reward individual contributions. Starting from a questionnaire, the informal network, which ignores the vertical relation among supervisor and employees, is created and a Centrality Index, based on the employee connections, has been defined and used to proxy the performance of employees. The main goals of the paper are to understand if the two mechanisms of monetary incentive distribution affect the employee performance, to analyze the variables that influence the employee performance, and therefore to identify the role of monetary incentives. The linear regression methodology has been chosen as a tool of analysis. Results show that the distribution of monetary incentives according to merit criteria rewards the employee performance and has positive effects on the employee performance in the short term

heterogeneous information based artificial stock market

In this paper, an information-based artificial stock market is considered. The market is populated by heterogeneous agents that are seen as nodes of a sparsely connected graph. Agents trade a risky asset in exchange for cash. Besides the amount of cash and assets owned, each agent is characterized by a sentiment. Moreover, agents share their sentiments by means of interactions that are identified by the graph. Interactions are unidirectional and are supplied with heterogeneous weights. The agent's trading decision is based on sentiment and, consequently, the stock price process depends on the propagation of information among the interacting agents, on budget constraints and on market feedback. A central market maker (clearing house mechanism) determines the price process at the intersection of the demand and supply curves. Both closed- and open-market conditions are considered. The results point out the validity of the proposed model of information exchange among agents and are helpful for understanding the role of information in real markets. Under closed market conditions, the interaction among agents' sentiments yields a price process that reproduces the main stylized facts of real markets, e.g. the fat tails of the returns distributions and the clustering of volatility. Within open-market conditions, i.e. with an external cash inflow that results in asset price inflation, also the unitary root stylized fact is reproduced by the artificial stock market. Finally, the effects of model parameters on the properties of the artificial stock market are also addressed

The Size Variance Relationship of Business Firm Growth Rates

The relationship between the size and the variance of firm growth rates is known to follow an approximate power-law behavior $\sigma(S) \sim S^{-\beta(S)}$ where $S$ is the firm size and $\beta(S)\approx 0.2$ is an exponent weakly dependent on $S$. Here we show how a model of proportional growth which treats firms as classes composed of various number of units of variable size, can explain this size-variance dependence. In general, the model predicts that $\beta(S)$ must exhibit a crossover from $\beta(0)=0$ to $\beta(\infty)=1/2$. For a realistic set of parameters, $\beta(S)$ is approximately constant and can vary in the range from 0.14 to 0.2 depending on the average number of units in the firm. We test the model with a unique industry specific database in which firm sales are given in terms of the sum of the sales of all their products. We find that the model is consistent with the empirically observed size-variance relationship

A comparison of sacral neuromodulation vs. transvaginal electrical stimulation for the treatment of refractory overactive bladder: The impact on quality of life, body image, sexual function, and emotional well-being

Overactive bladder syndrome (OAB) is defined by the presence of urinary urgency, with or without urge incontinence, usually accompanied by an increase in urinary frequency and nocturia in the absence of urinary tract infections (UTI) or other diseases. The overall prevalence of OAB symptoms in the female population is reported to be 16.6% and increases with advancing age and menopause. The aetiology of OAB is not fully understood and is likely to affect a heterogeneous population of patients due to changes to their central and peripheral nervous systems. Although OAB is frequently associated with female sexual dysfunction (FSD), its real impact on sexual function in women has been evaluated only in a few studies. The first line of treatment for OAB includes behavioural modification and physical therapy, either as monotherapies or in combination. Many patients who have not had success in managing their symptoms with more conservative therapies may decide to resort to third-line treatments for refractory OAB. These treatments include neuromodulation therapies, particularly transvaginal electrical stimulation (TES) and sacral neuromodulation (SN). The aim of this short commentary is to provide an overview of the effectiveness of these treatments and of their impact on quality of life, body image, sexual function, and emotional well-being