•Developers star repositories mainly to show appreciation or to bookmark projects•3 out of 4 developers check the stars metric before using or contributing to projects•But developers also evaluate ...other factors, such as code quality and documentation•Fast growth in the number of stars is often a result of promotion in social sites•When ranking projects, we should check whether stars are result of active promotion
Besides a git-based version control system, GitHub integrates several social coding features. Particularly, GitHub users can star a repository, presumably to manifest interest or satisfaction with an open source project. However, the real and practical meaning of starring a project was never the subject of an in-depth and well-founded empirical investigation. Therefore, we provide in this paper a throughout study on the meaning, characteristics, and dynamic growth of GitHub stars. First, by surveying 791 developers, we report that three out of four developers consider the number of stars before using or contributing to a GitHub project. Then, we report a quantitative analysis on the characteristics of the top-5,000 most starred GitHub repositories. We propose four patterns to describe stars growth, which are derived after clustering the time series representing the number of stars of the studied repositories; we also reveal the perception of 115 developers about these growth patterns. To conclude, we provide a list of recommendations to open source project managers (e.g., on the importance of social media promotion) and to GitHub users and Software Engineering researchers (e.g., on the risks faced when selecting projects by GitHub stars).
•Non-linear 3D FE pushover analyses on eight existing masonry towers.•Preliminary modal analyses on complex 3D FE discretizations.•Comparison with simplified approaches suggested by Italian ...Guidelines on Cultural Heritage.•Utilization of elasto damaging 3D models for seismic vulnerability evaluation.•Comparative seismic analyses of masonry towers with different geometric features.
The seismic vulnerability assessment of eight historical masonry towers, located in the North-East region of Italy, is carried out by means of simplified approaches. Three-dimensional finite element models of the eight towers are created on the basis of geometrical data deduced from both existing available documentation and insitu surveys. First, preliminary eigen-frequency analyses are performed in order to obtain some basic information about the structural behavior of the different towers. Then, a simplified approach based on non-linear static pushover analyses is adopted for the seismic verification of the global performance of the eight towers. In order to avoid unnecessary complications due to the utilization of orthotropic damaging models requiring many material parameters, a damage plasticity approach is used for masonry. The essential aspects of the masonry material are reproduced with sufficient care, namely the very low tensile strength, damage in tension and crack-crushing in compression. From an overall analysis of the results, it can be observed that almost all the towers are able to resist the seismic action corresponding to Sag=0.1g, whereas the majority are unsafe at least along one geometric direction for Sag=0.2g. Finally, this study presents the evaluation of the seismic safety Index by means of the simplified sectional approach suggested by Italian Guidelines on Cultural Heritage. The collapse accelerations for the towers under consideration are compared and it is found that the results obtained with the different approaches are in a good agreement with a slight conservative trend for the simplified procedure proposed by Italian Guidelines.
The use of waste materials as alternative aggregates in cementitious mixtures is one of the most investigated practices to enhance eco-sustainability in the civil and construction sectors. For ...specific applications, these secondary raw materials can ensure adequate technological performance, minimizing the exploitation of natural resources and encouraging the circular disposal of industrial or municipal waste. Aiming to design and develop lightweight paving blocks for pedestrian or very light-traffic purposes (parking area, garage, sidewalk, or sports surfaces), this paper presents the material characterization of rubberized cement mortars using ground waste tire rubber (0-1 mm rubber powder and 1-3 mm rubber granules) to totally replace the mineral aggregates. Considering recommended requirements for concrete paving members in terms of mechanical strength, water drainage performance, acoustic attenuation, and dynamic and energy absorption behavior, a comprehensive laboratory testing is proposed for five different formulations varying the sand-rubber replacement level and the proportion ratio between the two rubber fractions. Tests highlighted positive and promising results to convert laboratory samples into pre-cast members. The "hot" finding of the work was to prove the feasibility of obtaining totally rubberized mortars (0
/
% of sand) with suitable engineering performance and enhanced eco-friendly features.
•Hybrid base isolation of a historical masonry church.•Unbonded fiber reinforced elastomeric isolators and shape memory alloy wires.•Increase of the energy dissipation capacity.•Detailed 3D FE models ...to characterize the cyclic behavior of UFREIs.•Abaqus user element (UEL) to represent the 3D behavior of the isolators for global analyses.
One of the most promising devices for seismic base isolation of structures is the Unbonded Fiber Reinforced Elastomeric Isolator (UFREI) due to its low manufacturing cost and horizontal stiffness. This paper investigates the possibility of combining UFREIs and shape memory alloy (SMA) wires to increase the energy dissipation capacity of the isolation system for the seismic protection of a historical masonry church. Detailed 3D finite element (FE) analyses are performed to characterize the response of UFREIs under cyclic displacements. The behavior of SMA is simulated through a thermomechanical constitutive model implemented in a user-defined material (UMAT) subroutine available in the software package Abaqus. To reduce the computational effort in non-linear dynamic analyses of large isolated structures, an Abaqus user element (UEL) is developed to represent the 3D behavior of the isolation system proposed in this study. Non-linear dynamic time history analyses are then carried out to evaluate the seismic response of a historical masonry church in different configurations (fixed-base model and model equipped with different base isolation systems) for moderate and severe seismic intensity levels. Numerical results show that the damage observed in the masonry church can be considerably reduced through the insertion of UFREIs. The utilization of SMA wires with a specific pre-strain significantly increases the energy dissipation capacity of the base isolation system and decreases the horizontal displacements of the masonry church.
Technology can assist and support both people with dementia (PWD) and caregivers. Recently, technology has begun to embed remote components. Timely with respect to the pandemic, the present work ...reviews the most recent literature on technology in dementia contexts together with the newest studies about technological support published until October 2020. The final aim is to provide a synthesis of the timeliest evidence upon which clinical and non-clinical decision-makers can rely to make choices about technology in the case of further pandemic waves.
A review of reviews was performed alongside a review of the studies run during the first pandemic wave. PsycInfo, CINAHL, and PubMed-online were the databases inspected for relevant papers published from January 2010.
The search identified 420 articles, 30 of which were reviews and nine of which were new studies meeting the inclusion criteria. Studies were first sorted according to the target population, then summarized thematically in a narrative synthesis. The studies targeting technologies for PWD were categorized as follows: monitoring and security purposes, sustaining daily life, and therapeutic interventions. Each category showed potential benefits. Differently, the interventions for caregivers were classified as informative, psycho-education programs, psychosocial-supportive, therapeutic, and cognitive/physical training. Benefits to mental health, skills learning, and social aspects emerged.
The evidence shows that technology is well-accepted and can support PWD and caregivers to bypass physical and environmental problems both during regular times and during future pandemic waves. Nevertheless, the lack of a common methodological background is revealed by this analysis. Further and more standardized research is necessary to improve the implementation of technologies in everyday life while respecting the necessary personalization.
This article tests the suitability of a new method to monitor the degree of substitution of cellulose acetate films, by employing a compact and inexpensive near-infrared miniaturized spectrometer ...(908.1–1676.2 nm) that can be easily applied in situ. The present study compares the analytical performance of the proposed method against conventional diagnostic strategies based on benchtop micro-attenuated total reflectance Fourier transform Infrared (μATR -FTIR) measurements in the mid-infrared spectral range.
The novel calibration function exploits the shifts in the first overtone of the hydroxyl stretching 2νOH band of probe materials and was created using a set of analytical standards with different degrees of substitution. The robustness of the method was assessed by application on a group of sixteen historical cinematographic films. The accurate condition assessment of these films was performed in situ, in a non-invasive manner. The proposed analytical procedure is quick and easy-to-implement, and therefore it constitutes a rapid method to guide conservation strategies regarding film storage and digitalization in cultural institutions, including museums and cinematheques. Potential applications on three-dimensional objects and industrial processes are possible.
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•New reliable diagnostic method for cellulose acetate films.•High reliability of NIR for high DS samples due to sensibility towards 2νOH.•Deeper penetration depth of the system permits more representative results.•System is compact, simple, fast non-destructive, non-invasive, and inexpensive.•Industrial and museum tool to measure DS in acetate films and artifacts.
The recycling of waste tires is of paramount importance for environmental protection and
for economic reasons. The number of scrapped tires in the United States has reached 550
million per year and ...is still rising. Even higher numbers are estimated in the European
Union, reaching 1 billion tires per year. Disused tires create waste with a highly
negative environmental impact. Tire disposal mainly involves highly polluting treatments
(e.g. combustion processes to produce fuel oil), with only a small percentage of waste (3%
to 15%) destined for less-invasive treatments such as powdering. In this article we will
look at previous studies in which different amounts of waste tire powder are combined with
cement concrete mixtures to provide a final product with mechanical properties suitable
for engineering applications. Previous work has shown that a good compressive strength can
be achieved through replacing 30% of powdered tire with crushed sand. First, as the
percentage of aggregation between crumb rubber and crushed sand increases, compressive
strength decreases. Second, aggregation replacement of crumb rubber and crushed sand shows
a reduction in density at around 10%. Third, the modulus of elasticity depends on the
percentages added: the more rubber added to concrete, the less elastic the product will
be. In addition, a less tough concrete means higher strength. However, adding rubber to
concrete increases the toughness.1
Up to now, fiber-reinforced composites with thermoplastic matrix have seen limited fields of use in the structural scope due to their high viscosity in the molten state, which results in poor ...impregnability of the reinforcement, leading to mechanical properties of the finished product that are not comparable to those of thermosets. Although the latter still dominate the various sectors of automotive, aerospace, transportation and construction, new applications involving the production of thermoplastic composites are growing rapidly, offering new approaches to the solution of this problem. The aim of this work is to study and evaluate the state of the art on the manufacturing processes of thermoplastic matrix composite, analyzing the parameters that come into play and that most influence the process and material performance. The advantages of film stacking and powder impregnation techniques are contrasted by the versatility of hybrid fabrics and, at the same time, parameters such as pressure and temperature must be carefully considered. A description of different thermoplastic composite processes such as powder impregnation, film stacking molding, hybrid woven fabric, hybrid yarn and products follows, which represent the current possibilities to move from a thermosetting matrix composite to a thermoplastic one, upon which the concept of sustainability is based. This article wants to present an overview of research that has been done in manufacturing thermoplastic reinforced composites and will serve as a baseline and aid for further research and development efforts.
•Seismic assessment and earthquake response of slender historical masonry bell towers.•Seismic response is affected by the main geometrical features and main vibration properties of the bell ...towers.•Damage distribution among the different parts of the bell towers for different PGA values.•Influence of different accelerograms on the energy density dissipated by tensile damage and maximum top displacements.•Main limitations of the simplified approach are highlighted through a comparison with non-linear dynamic analyses.
Masonry bell towers represent a large portion of the Italian cultural heritage and are highly vulnerable to seismic actions mainly due to their relevant slenderness, as also observed in recent seismic events. The present study investigates the seismic vulnerability and earthquake response of five slender historical masonry bell towers, which are located in South-East Lombardia (Northern Italy), through a preliminary simplified procedure suggested by the Italian Code and advanced numerical simulations. To thoroughly study the seismic response of the bell towers, detailed three-dimensional FE models with a damage plasticity constitutive law for masonry are developed and non-linear dynamic analyses are performed using different accelerograms. The results of the non-linear dynamic analyses show that the geometrical features and the main vibration properties of the bell towers turn out to be the main parameters influencing the seismic performance of such a construction typology. Moreover, it can be noted a clear influence of the accelerograms characteristics on both the energy dissipated by tensile damage and the maximum normalized displacements of the bell towers. On the other hand, the structural geometrical characteristics play a very important role in terms of damage distribution among the different parts of the bell towers. In addition, the main limitations of the simplified approach suggested by the Italian Code for the seismic assessment of the bell towers under study are highlighted through a comparison with the results obtained from non-linear dynamic analyses. The main outcomes presented in this study may also represent a useful insight to better understand the earthquake response and seismic vulnerability of similar masonry bell towers located in the same region, providing valuable information that can be directly used in seismic risk assessment at regional scale.
Celluloid artifacts are known by conservation professionals to be prone to degradation, threatening their own integrity and that of nearby heritage collections. Celluloid alteration can have a ...heterogeneous nature, and this research topic is still in its infancy for heritage science. This article investigates degradation gradients, both along depth and width, of artificially aged celluloid sheets, and compares them to three-dimensional (3D) historical objects with the aim of gaining a better insight into the nature and evolution of their decay. ATR-FTIR was used to systematically study different sampling points of the artificially and naturally aged specimens and allowed us to recognize better-preserved surfaces and more deteriorated cores. ATR-FTIR was found suitable for assessing the molecular changes induced by degradation, particularly denitration and formation of carbonyl-containing degradation products in severely aged specimens. Even though the severely artificially aged sheets displayed unusual alteration phenomena, they present a degradation gradient similar to the one observed for the naturally aged 3D objects under study. This research underlines that sampling at different depths and/or widths is relevant for characterizing the heterogeneity of degraded celluloid, and further investigation with chromatographic techniques would greatly benefit the understanding of the complex degradation of celluloid artifacts.
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