Depth-averaged momentum equation for gravity currents with varying density : coefficient in pressure term

The second author is funded by the Swiss National Science Foundation (grant 200021 159249).Peer reviewedPostprin

Continuously Fed Density Currents Over Porous Bed

Gravity currents impact significantly the environment and human's life. Understanding their internal structure and their dynamics is fundamental for modelling purposes. In this study we observe experimentally how bed porosity affects the dynamics of density currents. We will focus on density and velocity profiles of currents traveling over porous bed, sinking and entraining water from its cavities. This abstract presents the preliminary results of this study which are relative to density currents travelling over the reference substratum, a smooth impermeable bed. The tests presented will be used as a reference to observe how the water entrained from the bottom cavities can change the structure of the current and are herein used to validate the experimental techniques. Brine water is injected at constant discharge in a 7.5 m long, 0.3 m wide and 0.3 m deep flume while instantaneous velocity and density profiles are simultaneously acquired 3 m downstream of the inlet. Initial excess densities and inlet velocities allow to reproduce gravity flows in sub and super-critical regime

Investigation of venting turbidity currents in the Rudbar-Lorestan reservoir in Iran

Venting of turbidity currents is known as an efficient measure to prevent reservoir sedimentation and is applied in many reservoirs globally. It has several economic and ecological advantages compared with other evacuation methods. In the literature, numerous researchers mentioned the importance of venting, but mostly qualitatively. Given the complexity of the phenomenon and the presence of many parameters affecting the efficiency of venting, case studies offer good insight into solutions for specific reservoirs where there is a high probability of occurrence of turbidity currents. In the present study, the efficiency of venting turbidity currents is investigated for Lorestan Reservoir in Iran. For that purpose, 3D numerical simulations of turbidity currents over 11 km and venting operation are performed using ANSYS Inc. software. The results of the present research allow to optimize venting operations in the Lorestan Reservoir and reservoirs having similar general characteristics. Recommendations are drawn on outlet opening timing and discharge allowing to vent the greater amount of sediments while minimizing the water release

Different Cyberbullying Experiences and Sensemaking Processes about the Sociocultural Context

Introduction: Cyberbullying represents one of the main current concerns of parents, educators and clinicians on youth. It consists of aggressive, offensive and injurious behaviors against a person by means of electronic device and sharing abusive content on the web. Previous studies have highlighted that cyberbullying is associated with individual factors, such as personality traits, age, sex and status, often disregarding the value attributed to one's own context of life. According to the Semiotic Dynamic Cultural Psychology Theory (SDPCT), the cultural context can be conceived as a net of interconnected trajectories of meanings, grounding the way of perceiving and experiencing a social environment, and enabling individuals to orient themselves in their material and social world. Aims: The present research aims to explore the relation between directly acted, suffered and indirectly observed behaviors of cyberbullying, the fear to be victim, the awareness of its harmfulness and sensemaking processes of one’s own context. Method: Six hundred twenty-four high school students (Mean AGE = 16.10; SD = 1.60) participated in this study. Participants filled in a questionnaire, consisting of two parts. The former was composed by six scales constructed ad hoc to explore the experience of acted, suffered and observed cyberbullying, the fear of being cyberbullied and the awareness of cyberbullying’s harmfulness. The latter the View of Context (VOC) questionnaire was used to map sensemaking processes through which people interpret their social context. Findings: Results shows significant associations between acted and suffered forms of cyberbullying, between fear of cyberbullying and the awareness of its harmfulness. The acted cyberbullying and suffered cyberbullying are both associated with representation of the context as devaluated (family, schools, social institutions are considered not welcoming, useful or reliable) and deprived of opportunities for the future. Conclusion: On clinical plan, the study suggests the importance of considering the relationships between bullying experienced and acted upon, as well as the role of meaning-making processes in understanding phenomena of social prevarication

Increasing the effectiveness of combined strikers in the defeat of lightly armored targets

The article deals with the possibility of increasing the damaging effects of small-caliber artillery ammunition in the fuel tanks of aircraft and helicopters. A comparison of the results of the calculation of the probability of the incendiary effect of strikers based on fluoropolymers on diesel fuel was made. The calculations were carried out using the methods of “Fragment Criterion” and “Energy Balance”. © 2021 Institute of Physics Publishing. All rights reserved

Analisi teoriche e di campo per la caratterizzazione idrologica e geomorfologica di bacini idrografici montani

A partire da un lavoro di campo di georeferenziazione di teste di canali nel bacino del Noce è stata estratta la rete dal modello digitale del terreno.Facendo riferimento alle reti estratte si è valutato l'effetto geomorfologico e cinematico sulla distribuzione dei tempi di residenza.Inoltre è stata verificata l'invarianza degli esponenti delle distribuzioni di probabilità che descrivono la struttura del bacino, invarianza caratteristica delle strutture frattal

Continuously-fed density currents over impermeable and porous substrates

Gravity currents are buoyancy-driven flows having a significant impact on the environment and human life. They can be observed in a vast range of natural and anthropogenic scenarios, such as seawater and freshwater, the atmosphere, or industrial processes. Gravity currents transport sediments, nutrients, and oxygen in water bodies but they are also often dramatically involved in the spreading of contaminants and can represent a severe hazard to humans and infrastructures. The relevance of these phenomena has motivated extensive research on gravity currents such as the present study which addresses two main different research objectives. The first objective of this research concerns the modeling of gravity currents with Shallow Water Equations (SWE). Large Eddy Simulations data of continuously-fed gravity currents are used to discuss how the chosen definition of current depth affects the value of the coefficients appearing in the SW continuity and momentum equations due to the non-uniformity of the vertical distribution of flow variables. Moreover, the implications that different definitions of current depth have on research findings and entrainment parameterization are discussed. This analysis showed that coefficients appearing in the momentum equation might significantly (up to $30\%$) differ from one, depending on the chosen current depth definition. On the contrary, the coefficients appearing in the continuity equation were shown to be very close to one. The second main research objective was to study how the mean and turbulent structure of a density current changes when it propagates over a porous substrate and to characterize the volume exchanges occurring at its lower interface. Experiments were carried out in the Laboratory of Hydraulic Constructions at EPFL to reproduce continuously-fed density (saline) currents, which propagated first over a smooth horizontal bed and then over a porous substrate of limited length. Inflow discharge, initial excess density, substrate porosity, and downstream confinement of the substrate were systematically varied. An image analysis technique was developed to monitor the flow density evolution above the substrate and within its pores. Simultaneously, an Acoustic Doppler Velocimetry Profiler acquires a quasi-instantaneous 3D vertical velocity profile over the substrate. Experimental results showed that, after an initial phase during which the current sinks into the substrate, freshwater entrainment from the substrate pores starts. Consequently, a mixing layer gradually forms at the lower boundary of the current. Its presence affects the mean density, mean velocity, and turbulent field primarily in the near-bed region, where buoyancy contributes to turbulent kinetic energy generation together with shear. Moreover, at the porous substrate interface, buoyancy instabilities enhance the bed-normal momentum flux, increasing the bulk flow resistance. As a consequence, although the no-slip boundary condition results in lower friction losses, the shear velocity increases with the porosity of the substrate. In addition, experimental measurements allowed to quantify the current volume loss and the ambient-fluid entrainment from the substrate pores. The main drivers of these exchanges are discussed. The study of the entrainment of ambient-fluid from the bottom is fundamental to understand and model the resuspension of substances, such as nutrients and pollutants, present in the porous substrates

The concept of context in the field of addiction research. A review

Objective: In the field of addiction research, the studies have typically focused on the identification of individual factors that affect the onset and maintenance of addictive behaviors. However, during the last 20 years, there has been a growing interest in the role of social and cultural factors and efforts have also been made to re-situate addicts in their social environment. The authors reviewed the literature on addictions with the purpose of investigating how scholars have conceptualized and incorporated contextual influences in their work. Method: Studies investigating different aspects of the “context”, published in the period 2012-2014 in one of the most representative journal in the field, were analyzed. Results: From a total of 126 studies examined, 14 macro-categories and 56 sub-categories were identified. Most of the articles identify the context with the socio-demographic variables, the exposition to addictive behaviors in the social environment and different social and familiar factors (like media influence, parental style, etc); Conclusions: Currently, there is a huge variability in the way of defining and analyzing the role of context. Only few studies addressed the role of culture. The view of culture as the context-container to which individuals belong emerges, with a little recognition of the role of individuals in negotiating their cultural world and the meaning of their experience

The concept of context in the field of addiction research. A review

In the field of addiction research, studies have typically focused on the identification of individual factors that affect the onset and maintenance of addictive behaviors. However, there has been growing interest in the role of social and cultural factors. The authors reviewed the literature on addictions with the purpose of investigating how scholars have conceptualized and incorporated contextual influences in their work. An analysis was made of studies investigating “context”, in the period 2012-2014, in one of the most representative journals in the field. From a total of 142 studies examined, 14 macro-categories and 48 sub-categories were identified. Most of the articles identify context with socio-demographic variables, exposition to addictive behaviors in the social environment and different social and family factors. The review reveals that many studies lack an explicit theoretical model; furthermore, there is a huge variability in the way of defining and analyzing the role of context; only a few studies addressed the role of culture and the meaning of the experience

Subjective culturer, smoking, alcohol and the Internet dependence

Cross cultural, ethnographic, anthropological studies, as well as research in the field of developmental and cultural psychopathology, give evidence in support of the idea that “context” (interpersonal environment, conventional social structures, social norms, socio-economic variables, cultural factors) plays a main role in defining which expression of distress is accepted or sanctioned (Draguns, 1995; Gone & Kirmayer, 2010). Different studies show how acculturation plays an important role in the initiation and maintenance of a number of mental illnesses (Oei & Raylu, 2009). According to the cultural standpoint, our work focuses on the role of the subjects’ cultures in many types of problematic repetitive behaviors, like smoking, alcohol and internet addictions. The term “subjective culture” can be originally found in Triandis (1972, 2002). According to the author, subjective culture includes ideas about how to live properly and how to behave in relation to objects and people. However, whereas for the author subjective culture is a “characteristic way of perceiving its social environment" by society (Triandis, 1972, p. viii, 3), we recognize that many subjective cultures may be expressed within the same society (Venuleo, Salvatore, & Mossi, 2014; Venuleo, Mossi, & Salvatore, 2014; Venuleo & Marinaci, forthcoming). Previous studies in the Italian context have already provided evidence that subjective cultures, through which people interpret their social environment, play a major role in differentiating heavy drinkers, as well as pathological gamblers, compared with a control group (Venuleo, Salvatore, & Mossi, 2014). The current study assessed whether smoking dependent subjects express different subjective cultures compared with alcohol dependent subjects and internet dependent subjects. Our hypothesis is that subjective cultures also play a role in differentiating various kinds of addiction, having different implications for individuals’ social adapting, Participants, recruited in three different contexts (public health services for the treatment of addiction, casino, undergraduate course) were subjected to the Cigarette Dependence Scale (CDS) (J-F. Etter, J. Le Houezec & T. V. Perneger 2003), the Alcohol Use Disorders Identification Test (AUDIT) (World Health Organization 1993), the Internet Addiction Test (IAT) (K. Young 1998), and the Questionnaire on the Interpretation of the Social Environment (QUISE) (Mossi & Salvatore 2011), in order to investigate the subjective cultures. Two different logistic regressions were applied in order to esteem the capability of the QUISE scores to differentiate smoking dependent subjects from alcohol dependent subjects and internet dependent subjects. Consistent with the hypothesis, the results show that smoking dependent subjects express a different way of connoting the social environment, when compared with alcohol dependent and internet dependent subjects. The former depict the environment as positive and reliable, while the the latter depict it as negative and unreliable. Implications for prevention and intervention efforts are discussed