What can we learn from multi-objective meta-optimization of Evolutionary Algorithms in continuous domains?

Properly configuring Evolutionary Algorithms (EAs) is a challenging task made difficult by many different details that affect EAs' performance, such as the properties of the fitness function, time and computational constraints, and many others. EAs' meta-optimization methods, in which a metaheuristic is used to tune the parameters of another (lower-level) metaheuristic which optimizes a given target function, most often rely on the optimization of a single property of the lower-level method. In this paper, we show that by using a multi-objective genetic algorithm to tune an EA, it is possible not only to find good parameter sets considering more objectives at the same time but also to derive generalizable results which can provide guidelines for designing EA-based applications. In particular, we present a general framework for multi-objective meta-optimization, to show that "going multi-objective" allows one to generate configurations that, besides optimally fitting an EA to a given problem, also perform well on previously unseen ones

An Application Of Artificial Immune System In A Wastewater Treatment Plant

Guaranteeing the continuity and the quality of services in network plants is a key issue in the research area of asset management. Especially when the plants are located in a wide area where machines are not continuously monitored by the operators. In particular, the pervasive adoption of smart sensors could be able to develop intelligent maintenance system through an elaboration of data coming from the machines: this data could be processed by diagnostics algorithms to warn preventively the fault status of the components or machines monitored. The algorithms’ structure is contained in a multiple system of agents that have different tasks to manage both the single machine and the information exchanged within the whole system. This paper aims to present an application of Artificial Immune System defining, for each plant section, the kind of agents employed and the related sensors that must be adopted to collect the useful data. In order to provide a practical example, the structure of an Artificial Immune System has been implemented in a wastewater treatment plant where the agents are tested with noteworthy results. © 20164928556

Cement-Based Radiative Coolers for Photovoltaics: Towards a Practical Design

In 2014, the experimental realization of radiative coolers capable of reaching sub-ambient temperatures under direct sunlight has opened up new possibilities for the thermal management of solar cells. Radiative coolers eject excess heat by emitting thermal radiation within the so-called atmosphere transparency window. The completely passive nature of this process and its reliance on material properties only, make radiative coolers extremely attractive in terms of energy efficiency. Integrated with a photovoltaic cell, the radiative cooler can reduce the cell operating temperature, leading to high efficiency and lifetime gains. Yet, most radiative coolers in the literature are metamaterials with scarce elements or complex fabrications processes, or organic materials with potential UV instability, with questionable economic viability or reliability. To address this problem, we have recently proposed cement-based materials as a low-cost, scalable and stable solution for photovoltaics cooling, showing that their electromagnetic properties can be tuned to maximize their thermal emissivity by acting on their microstructure. In particular, using a detailed balance model, we have demonstrated that their cooling performance could increase the efficiency of silicon solar cells by up to 9% and extended their lifetime by up to 4 times. In this work, we take a further step towards the experimental realization of this attractive concept, by investigating possible approaches, requirements and prospects for the practical design of photovoltaic systems employing cement-based radiative coolers

Bending and shear behavior of historic walls strengthened with composite reinforced mortar

Composite reinforced mortar (CRM) is a relatively new solution for the strengthening of existing masonry members that comprises fiber-reinforced polymer (FRP) grids reinforcing inorganic mortar overlays. CRMs were proven to be effective in strengthening masonry members against in- and out-of- plane loads. In this paper, a glass FRP-CRM is employed to strengthen 5-leaf historic masonry walls cut from an existing building located in Milan, Italy. The walls were strengthened and then subjected to three-point bending and diagonal compression tests. Results were compared with those of corresponding non-strengthened walls and showed the CRM effectiveness also in the case of thick masonry members

Effect of salt crystallization on the bond behavior of glass FRCM-masonry joints

The use of fabric-reinforced cementitious matrix (FRCM) composites for reinforcement of existing masonry members has attracted an increasing interest in recent years. FRCM composites are particularly suitable for masonry strengthening and retrofitting due to their ease of installation, reversibility, excellent compatibility with the substrate and vapor permeability. Tensile mechanical properties and bond behavior of FRCM composites were extensively studied. However, limited information is available regarding the durability of FRCM and FRCM-strengthened members, which may represent a critical issue for the effectiveness of the strengthening system. Indeed, existing masonry structures suffer from the presence of moisture, which can come from rising damp, condensation, infiltration of rainwater, etc. Water is often responsible for the presence of salt within the element, which represents a major cause of masonry damage. When the salt crystallization takes place at the interface between the FRCM and the substrate, a possible reduction of the FRCM bond capacity can be observed. In this paper, the effect of salt crystallization on the bond behavior of an FRCM applied onto a masonry substrate is experimentally investigated. The FRCM composite employed comprises a glass open mesh reinforcing textile and a cementitious matrix. FRCM-masonry joints were conditioned in a saline solution to induce salt crystallization in the FRCM, i.e., within the composite strips and at the FRCM-masonry interface. The bond behavior of the FRCM composite before and after the conditioning is investigated with single-lap direct shear tests. The results obtained provide information on the long-term behavior of the glass FRCM composite considered

Emotion-based analysis of programming languages on Stack Overflow

When developing a software engineering project, selecting the most appropriate programming language is a crucial step. Most often, feeling at ease with the possible options becomes almost as relevant as the technical features of the language. Therefore, it appears to be worth analyzing the role that the emotional component plays in this process. In this article, we analyze the trend of the emotions expressed by developers in 2018 on the Stack Overflow platform in posts concerning 26 programming languages. To do so, we propose a learning model trained by distant supervision and the comparison of two different classifier architectures

Radiative Cooling of Solar Cells with Cement-Based Materials

Lowering the operating temperature of solar cells can increase efficiency and lifespan of these devices. Among the available thermal management options, radiative cooling shines because of its passive nature and systemic simplicity. Unfortunately, the applicability of most radiative coolers to industrial manufacturing is questioned by high cost or UV instability. We have recently shown that stable and cost-effective cement-based materials can be designed to be suitable radiative coolers for solar cells. However, we have done so in line with the literature, by modeling the solar cell in the radiative limit and neglecting the thermal contact resistance at the cell/cooler interface, which might actually be large enough to hinder heat transfer because of the poor adhesion properties of cement-based materials. In this work, we have generalized the model used to assess radiative coolers by incorporating solar cell non-radiative losses (Auger, Shockley-Read-Hall) and a thermal barrier between cell and cooler. The final model provides a description of the thermal behavior of a solar cell with radiative cooler closer to reality, while preserving the transparency of the detailed-balance approach, that has allowed us to better assess these systems and provide design guidelines, with focus on cement-based radiative coolers

Extended detailed balance modeling toward solar cells with cement-based radiative coolers

Research conducted in the framework of MIRACLE Project (Photonic Metaconcrete with Infrared RAdiative Cooling capacity for Large Energy savings, GA 964450), coordinated by Dr. Jorge Sánchez Dolado, from Centro de Física de Materiales (CFM).Reducing the temperature of a solar cell increases its efficiency and lifetime. This can be achieved by radiative cooling, a passive and simple method relying on materials that dump heat into outer space by thermal emission within the atmosphere transparency window between 8 and (Formula presented.). As most radiative coolers are expensive or possibly UV unstable, we have recently proposed cement-based solutions as a robust and cost-effective alternative. However, the assessment model used describes the cell in the radiative limit and with perfect thermal coupling to the cooler, in line with the literature. In this work, we lift these two approximations, by incorporating Auger and Shockley–Read–Hall nonradiative recombination and a finite heat transfer coefficient at the cell/cooler interface, to obtain a thermal description of the cell/cooler stack closer to reality, while preserving the universality and transparency of the detailed-balance approach. We use this model to demonstrate that the cell performance gains provided by a radiative cooler are underestimated in the radiative limit and are hence more prominent in devices with stronger nonradiative recombination. Furthermore, we quantify the relation between cell temperature and heat transfer coefficient at the cell/cooler interface and show how this can be used to define design requirements. The extended model developed, and the resulting observations provide important guidelines toward the practical realization of novel radiative coolers for solar cells, including cement-based ones.This research was supported by the European Union's Horizon 2020 Research and Innovation Program under grant agreement no. 964450.Peer reviewe