Modeling Bed Shear Stress Distribution in Rectangular Channels Using the Entropic Parameter.

The evaluation of bed shear stress distribution is fundamental to predicting the transport of sediments and pollutants in rivers and to designing successful stable open channels. Such distribution cannot be determined easily as it depends on the velocity field, the shape of the cross section, and the bed roughness conditions. In recent years, information theory has been proven to be reliable for estimating shear stress along the wetted perimeter of open channels. The entropy models require the knowledge of the shear stress maximum and mean values to calculate the Lagrange multipliers, which are necessary to the resolution of the shear stress probability distribution function. This paper proposes a new formulation which stems from the maximization of the Tsallis entropy and simplifies the calculation of the Lagrange coefficients in order to estimate the bed shear stress distribution in open-channel flows. This formulation introduces a relationship between the dimensionless mean shear stress and the entropic parameter which is based on the ratio between the observed mean and maximum velocity of an open-channel cross section. The validity of the derived expression was tested on a large set of literature laboratory measurements in rectangular cross sections having different bed and sidewall roughness conditions as well as various water discharges and flow depths. A detailed error analysis showed good agreement with the experimental data, which allowed linking the small-scale dynamic processes to the large-scale kinematic ones.

Entropy Wake Law for Streamwise Velocity Profiles in Smooth Rectangular Open Channels.

In narrow open channels, the three-dimensional nature of the flow and the transport momentum from the sidewalls to the central region cause the maximum longitudinal velocity to occur below the water surface. The entropy model is unable to accurately describe the velocities near the free surface when the dip phenomenon exists. The present paper proposes a new dip-modified entropy law for steady open channel flows, which consists of three additional terms: the first one similar to Coles' function; the second one linearly proportional to the logarithmic distance from the free surface; and the third one depending on the cubic correction near the maximum velocity. The validity of the new model was tested on a set of laboratory measurements carried out in a straight rectangular flume with smooth boundaries and for different values of water discharge, bottom slope, and aspect ratio. A detailed error analysis showed good agreement with the data measured through the present research and a more accurate prediction of the velocity-dip-position compared with the one evaluated through the original entropy model. In addition, the modified entropy wake law matched very well with other literature data collected in rectangular cross-sections with different flow conditions.

Information Entropy Theory Applied to the Dip-Phenomenon Analysis in Open Channel Flows.

The knowledge of the fluid discharge in free surface flows requires a great number of velocity measurements along the whole cross-section, taking up a large amount of time, using expensive equipment, and employing specialized labor. To overcome these obstacles, various models have been developed thus far that show how to estimate the mean velocity through the maximum velocity. In three-dimensional open channels, the maximum velocity can be located below the free surface because of the presence of secondary flows mainly originating by the sidewalls, an occurrence known as dip-phenomenon. In this condition, predicting the maximum velocity position is quite difficult and has always represented a challenge to most hydraulic engineers and researchers. In the present study, a mathematical model derived from the information entropy theory is proposed to evaluate the velocity-dip-position over the entire cross-section of both wide and narrow open channels, thus overcoming the limitations of the existing methods. Large literature measurement sets, collected in uniform and non-uniform flows, were used to test the validity of the model, showing good agreement with the experimental data and providing an accurate estimation of the dip-position.

AAC and Autism: Manual Signs and Pecs, a Comparison.

Autism Spectrum Disorders (ASD) represent a heterogeneous group of disorders, with onset in developmental age, which present a clinical expressiveness that varies from subject to subject and in the same subject over time. The DSM 5 defines Autism Spectrum Disorders according to two main criteria: persistent deficits in social communication and social interaction in multiple contexts and limited and repetitive patterns of behavior, interests or activities. This disorder can manifest itself across a broad spectrum of severity levels. Indeed, ASD includes clinical conditions from low functioning (LF-Low Functioning) to high functioning (HF-High Functioning), taking cognitive and adaptive functioning as a reference. One of the main characteristics of individuals with ASD is a delay in receptive and expressive communication. These deficits have led to the identification of evidence-based practices, particularly for those with severe communication difficulties. Augmentative Alternative Communication (AAC) has been implemented to compensate for deficits in functional communication and language skills in individuals with complex communication deficits. The AAC comprises communication systems including the Manual Signs, speech and image output devices (Communicators), and Image Exchange Systems (PECS); these systems have been shown to actually improve various abilities in autism such as social skills, modify and improve dysfunctional behaviors and, above all, improve learning. Recent meta-analyses have shown how PECS and Manual Sign can have great effects on the communication skills of young people with autism. The aim of this study is to compare these two types of intervention to improve communication in terms of vocalization in subjects with ASD and try to understand which of the two lead to more significant and rapid improvements.

Executive Functions and Foreign Language Learning.

Executive functions (EFs) serve as an umbrella term to describe a set of higher-order cognitive abilities that include working memory, inhibitory control, cognitive flexibility, planning, reasoning, and problem-solving. Various studies suggest that foreign language learning likely promotes executive functions, but others suggest that executive functions could improve foreign language learning. The aim of this study is to investigate the relationship between executive functions and foreign language learning and how these processes could interact. The sample included 64 children from kindergarten, aged 4-5 years, with no documented neuropsychiatric disorders, and from the middle-high literacy group. They were divided into three groups based on the level of their knowledge of the foreign language. A significant effect of the group on the executive tasks is shown in the comparison of the groups. Children who belonged to a group that had advanced foreign language proficiency had better results in executive tasks. Our results suggest that the higher the level of foreign language proficiency, the higher the performance of the executive tasks. However, we do not know if there is a causal effect between these variables.