A Distributed Approach for the Optimal Power Flow Problem Based on ADMM and Sequential Convex Approximations

The optimal power flow (OPF) problem, which plays a central role in operating electrical networks is considered. The problem is nonconvex and is in fact NP hard. Therefore, designing efficient algorithms of practical relevance is crucial, though their global optimality is not guaranteed. Existing semi-definite programming relaxation based approaches are restricted to OPF problems where zero duality holds. In this paper, an efficient novel method to address the general nonconvex OPF problem is investigated. The proposed method is based on alternating direction method of multipliers combined with sequential convex approximations. The global OPF problem is decomposed into smaller problems associated to each bus of the network, the solutions of which are coordinated via a light communication protocol. Therefore, the proposed method is highly scalable. The convergence properties of the proposed algorithm are mathematically substantiated. Finally, the proposed algorithm is evaluated on a number of test examples, where the convergence properties of the proposed algorithm are numerically substantiated and the performance is compared with a global optimal method.Comment: 14 page

Classical irreversible thermodynamics versus extended irreversible thermodynamics: the role of the continuity equation

This brief note focuses on a simple fluid, i.e., a homogeneous, chemically inert, and electrically neutral fluid, for which, in the linear non-equilibrium regime, the thermodynamic state is expressed by a relation between pressure, temperature, and density. The approach based on the elementary scales is used to check the validity range of both the classical irreversible thermodynamics and the extended irreversible thermodynamics. The achieved result reveals that the classical irreversible thermodynamics fails in providing arm adequate response when the mechanical solicitations exceed limit values

Beach drainage system: a comprehensive review of a controversial soft-engineering method

The beach drainage can be included among the soft engineering methods aimed to counteract the shoreline retreat related to the sediment redistribution along the beach profile. The idea that the groundwater table plays a role in the mobilization of the sediment grains underlies the application of the beach drainage system (BDS) as a tool able to modify the natural dynamics of groundwater table at sandy beaches. Indeed, BDS consists of a series of alongshore buried drains aimed to lower the groundwater table. Due to the drainage, the thickening of the layer of dry sand makes the solid grains less prone to be mobilized by the action of the waves at the swash zone, where interaction phenomena between the percolating and the incoming water lens take place. This tool had a troubled history. Its first applications were encouraging. Since then, controversial performances of both experimental and prototype scale experiences have been observed around the world. This paper aims to present an up-to-date full review of the studies and experiments carried out so far, in order to provide the reader with a complete perspective on its strength and weakness as well as open challenges to be faced in the near future

Mapping and classification of ports and marinas for the definition of long-term development strategy

Mapping and classification of ports may be of great help to define effective development strategies based on the concept of “intelligent, green and integrated port”, within the frame of sustainable development. To this end, classification tools and knowledge of the initial situation are crucial points needed, just as an example, to boost the maritime and short-sea connectivity by promoting the creation of regional touristic port network, capable of implementing a smart, green, and integrated transport system. This work deals with the mapping and classification of ports and marinas. A possible methodology to define a priority matrix intervention rank is proposed and applied to all the harbors in the Puglia region, as a case study. The collected open data aim to describe several aspects: the services, the urban planning whereby the port is thought, the facilities and structures, the connection with multi-modal local transport. The mapping activity has been performed within the frame of the AI-SMART project funded by the European Regional Development Fund that aims to implement and develop a common port network in the Adriatic-Ionian area. The case study served to highlight the feasibility and applicability of the proposed method to a real case

Non-adenine based purines accelerate wound healing

Wound healing is a complex sequence of cellular and molecular processes that involves multiple cell types and biochemical mediators. Several growth factors have been identified that regulate tissue repair, including the neurotrophin nerve growth factor (NGF). As non-adenine based purines (NABPs) are known to promote cell proliferation and the release of growth factors, we investigated whether NABPs had an effect on wound healing. Full-thickness, excisional wound healing in healthy BALB/c mice was significantly accelerated by daily topical application of NABPs such as guanosine (50% closure by days 2.5′.8). Co-treatment of wounds with guanosine plus anti-NGF reversed the guanosine-promoted acceleration of wound healing, indicating that this effect of guanosine is mediated, at least in part, by NGF. Selective inhibitors of the NGF-inducible serine/threonine protein kinase (protein kinase N), such as 6-methylmercaptopurine riboside abolished the acceleration of wound healing caused by guanosine, confirming that activation of this enzyme is required for this effect of guanosine. Treatment of genetically diabetic BKS.Cg-m+/+lepr db mice, which display impaired wound healing, with guanosine led to accelerated healing of skin wounds (25% closure by days 2.8′.0). These results provide further confirmation that the NABP-mediated acceleration of cutaneous wound healing is mediated via an NGF-dependent mechanism. Thus, NABPs may offer an alternative and viable approach for the treatment of wounds in a clinical setting

Optimizing Client Association for Load Balancing and Fairness in Millimeter-Wave Wireless Networks

Millimeter-wave communications in the 60-GHz band are considered one of the key technologies for enabling multigigabit wireless access. However, the special characteristics of such a band pose major obstacles to the optimal utilization of the wireless resources, where the problem of efficient client association to access points (APs) is of vital importance. In this paper, the client association in 60-GHz wireless access networks is investigated. The AP utilization and the quality of the rapidly vanishing communication links are the control parameters. Because of the tricky non-convex and combinatorial nature of the client association optimization problem, a novel solution method is developed to guarantee balanced and fair resource allocation. A new distributed, lightweight, and easy-to-implement association algorithm, based on Lagrangian duality theory and subgradient methods, is proposed. It is shown that the algorithm is asymptotically optimal, that is, the relative duality gap diminishes to zero as the number of clients increases

Drains influence on the beach groundwater hydrodynamics

The aim of this paper is to investigate the role in the groundwater level dynamics played by drains of a Beach Drainage System (BDS) with different nominal diameters.Three different cases are considered: drained beach without incoming waves; undrained beach with incoming waves, and drained beach with incoming waves. Hence, a preliminary numerical investigation on the hydrodynamics inside a sandy beach is carried out, accounting for the presence of both short water waves and a BDS. The (Volume Averaged) Reynolds Averaged Navier Stokes (RANS) equations are solved by using the Finite Volume Method, and the Volume of Fluid (VOF) is used to track the groundwater table fluctuations by using an OpenFoam® solver. To represent the draining surface, the atmospheric pressure at the drain boundary is imposed. In order to reproduce the concentrated head losses, a low permeability layer around the drain is used. The model is able to catch the damped behaviour of the water table oscillation inside the sandy porous medium forced by the incoming short waves. In case of drained beaches, the drain dimensions play an important role in the outflow velocities at the boundary of the pipe. On the other hand, the drain diameter does not affect the general behaviour of the groundwater level inside the beach, but within an area close to the drain location

Elementary scales and the lack of Fourier paradox for Fourier fluids

Focusing on the Fourier fluids in the liquid state, which are characterized by linear thermal constitutive equation and low compressibility, this short note proposes a discrete approach based on the elementary scales, which allows removing the so-called Fourier paradox in classical continuum thermomechanics. As a corollary, the adopted line of reasoning allows highlighting some features on the elementary scales